Radiotion Therapy

What is radiation therapy?

Radiation therapy uses high-energy radiation to shrink tumors and kill cancer cells . X-rays, gamma rays, and charged particles are types of radiation used for cancer treatment.

The radiation may be delivered by a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy, also called brachytherapy).

Systemic radiation therapy uses radioactive substances, such as radioactive iodine, that travel in the blood to kill cancer cells.

About half of all cancer patients receive some type of radiation therapy sometime during the course of their treatment.

How does radiation therapy kill cancer cells?

Radiation therapy kills cancer cells by damaging their DNA (the molecules inside cells that carry genetic information and pass it from one generation to the next). Radiation therapy can either damage DNA directly or create charged particles (free radicals) within the cells that can in turn damage the DNA.

Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and eliminated by the body’s natural processes.

Does radiation therapy kill only cancer cells?

No, radiation therapy can also damage normal cells, leading to side effects.

Doctors take potential damage to normal cells into account when planning a course of radiation therapy. The amount of radiation that normal tissue can safely receive is known for all parts of the body. Doctors use this information to help them decide where to aim radiation during treatment.

Why do patients receive radiation therapy?

Radiation therapy is sometimes given with curative intent (that is, with the hope that the treatment will cure a cancer, either by eliminating a tumor, preventing cancer recurrence, or both). In such cases, radiation therapy may be used alone or in combination with surgery, chemotherapy, or both.

Radiation therapy may also be given with palliative intent. Palliative treatments are not intended to cure. Instead, they relieve symptoms and reduce the suffering caused by cancer.

Some examples of palliative radiation therapy are:

• Radiation given to the brain to shrink tumors formed from cancer cells that have spread to the brain from another part of the body (metastases).
• Radiation given to shrink a tumor that is pressing on the spine or growing within a bone, which can cause pain.
• Radiation given to shrink a tumor near the esophagus, which can interfere with a patient’s ability to eat and drink.

How is radiation therapy planned for an individual patient?

A radiation oncologist develops a patient’s treatment plan through a process called treatment planning, which begins with simulation.
During simulation, detailed imaging scans show the location of a patient’s tumor and the normal areas around it. These scans are usually computed tomography (CT) scans, but they can also include magnetic resonance imaging (MRI), positron emission tomography (PET), and ultrasound scans.

Computed Tomography Scanner. CT scans are often used in treatment planning for radiation therapy. During CT scanning, pictures of the inside of the body are created by a computer linked to an x-ray machine.

During simulation and daily treatments, it is necessary to ensure that the patient will be in exactly the same position every day relative to the machine delivering the treatment or doing the imaging. Body molds, head masks, or other devices may be constructed for an individual patient to make it easier for a patient to stay still. Temporary skin marks and even tattoos are used to help with precise patient positioning.

Patients getting radiation to the head may need a mask. The mask helps keep the head from moving so that the patient is in the exact same position for each treatment.

After simulation, the radiation oncologist then determines the exact area that will be treated, the total radiation dose that will be delivered to the tumor, how much dose will be allowed for the normal tissues around the tumor, and the safest angles (paths) for radiation delivery.

The staff working with the radiation oncologist (including physicists and dosimetrists) use sophisticated computers to design the details of the exact radiation plan that will be used. After approving the plan, the radiation oncologist authorizes the start of treatment. On the first day of treatment, and usually at least weekly after that, many checks are made to ensure that the treatments are being delivered exactly the way they were planned.

Radiation doses for cancer treatment are measured in a unit called a gray (Gy), which is a measure of the amount of radiation energy absorbed by 1 kilogram of human tissue. Different doses of radiation are needed to kill different types of cancer cells.

Radiation can damage some types of normal tissue more easily than others. For example, the reproductive organs (testicles and ovaries) are more sensitive to radiation than bones. The radiation oncologist takes all of this information into account during treatment planning.
If an area of the body has previously been treated with radiation therapy, a patient may not be able to have radiation therapy to that area a second time, depending on how much radiation was given during the initial treatment. If one area of the body has already received the maximum safe lifetime dose of radiation, another area might still be treated with radiation therapy if the distance between the two areas is large enough.

The area selected for treatment usually includes the whole tumor plus a small amount of normal tissue surrounding the tumor. The normal tissue is treated for two main reasons:

• To take into account body movement from breathing and normal movement of the organs within the body, which can change the location of a tumor between treatments.
• To reduce the likelihood of tumor recurrence from cancer cells that have spread to the normal tissue next to the tumor (called microscopic local spread).

How is radiation therapy given to patients?

Radiation can come from a machine outside the body (external-beam radiation therapy) or from radioactive material placed in the body near cancer cells (internal radiation therapy, more commonly called brachytherapy). Systemic radiation therapy uses a radioactive substance, given by mouth or into a vein, that travels in the blood to tissues throughout the body.
The type of radiation therapy prescribed by a radiation oncologist depends on many factors, including:

• The type of cancer.
• The size of the cancer.
• The cancer’s location in the body.
• How close the cancer is to normal tissues that are sensitive to radiation.
• How far into the body the radiation needs to travel.
• The patient’s general health and medical history.
• Whether the patient will have other types of cancer treatment.
• Other factors, such as the patient’s age and other medical conditions.

External-beam radiation therapy
External-beam radiation therapy is most often delivered in the form of photon beams (either x-rays or gamma rays). A photon is the basic unit of light and other forms of electromagnetic radiation. It can be thought of as a bundle of energy. The amount of energy in a photon can vary. For example, the photons in gamma rays have the highest energy, followed by the photons in x-rays.

Linear Accelerator Used for External-beam Radiation Therapy.
Many types of external-beam radiation therapy are delivered using a machine called a linear accelerator (also called a LINAC). A LINAC uses electricity to form a stream of fast-moving subatomic particles. This creates high-energy radiation that may be used to treat cancer.

Patients usually receive external-beam radiation therapy in daily treatment sessions over the course of several weeks. The number of treatment sessions depends on many factors, including the total radiation dose that will be given.

One of the most common types of external-beam radiation therapy is called 3-dimensional conformal radiation therapy (3D-CRT). 3D-CRT uses very sophisticated computer software and advanced treatment machines to deliver radiation to very precisely shaped target areas.

Many other methods of external-beam radiation therapy are currently being tested and used in cancer treatment. These methods include:

• Intensity-modulated radiation therapy (IMRT): IMRT uses hundreds of tiny radiation beam-shaping devices, called collimators, to deliver a single dose of radiation (2). The collimators can be stationary or can move during treatment, allowing the intensity of the radiation beams to change during treatment sessions. This kind of dose modulation allows different areas of a tumor or nearby tissues to receive different doses of radiation.
  Unlike other types of radiation therapy, IMRT is planned in reverse (called inverse treatment planning). In inverse treatment planning, the radiation oncologist chooses the radiation doses to different areas of the tumor and surrounding tissue, and then a high-powered computer program calculates the required number of beams and angles of the radiation treatment (3). In contrast, during traditional (forward) treatment planning, the radiation oncologist chooses the number and angles of the radiation beams in advance and computers calculate how much dose will be delivered from each of the planned beams.
• The goal of IMRT is to increase the radiation dose to the areas that need it and reduce radiation exposure to specific sensitive areas of surrounding normal tissue. Compared with 3D-CRT, IMRT can reduce the risk of some side effects, such as damage to the salivary glands (which can cause dry mouth, or xerostomia), when the head and neck are treated with radiation therapy (4). However, with IMRT, a larger volume of normal tissue overall is exposed to radiation. Whether IMRT leads to improved control of tumor growth and better survival compared with 3D-CRT is not yet known (4).
• Image-guided radiation therapy (IGRT): In IGRT, repeated imaging scans (CT, MRI, or PET) are performed during treatment. These imaging scans are processed by computers to identify changes in a tumor’s size and location due to treatment and to allow the position of the patient or the planned radiation dose to be adjusted during treatment as needed. Repeated imaging can increase the accuracy of radiation treatment and may allow reductions in the planned volume of tissue to be treated, thereby decreasing the total radiation dose to normal tissue (5).
• Tomotherapy: Tomotherapy is a type of image-guided IMRT. A tomotherapy machine is a hybrid between a CT imaging scanner and an external-beam radiation therapy machine (6). The part of the tomotherapy machine that delivers radiation for both imaging and treatment can rotate completely around the patient in the same manner as a normal CT scanner. Tomotherapy machines can capture CT images of the patient’s tumor immediately before treatment sessions, to allow for very precise tumor targeting and sparing of normal tissue.
  Like standard IMRT, tomotherapy may be better than 3D-CRT at sparing normal tissue from high radiation doses (7). However, clinical trials comparing 3D-CRT with tomotherapy have not been conducted.
• Stereotactic radiosurgery: Stereotactic radiosurgery (SRS) can deliver one or more high doses of radiation to a small tumor (5, 8). SRS uses extremely accurate image-guided tumor targeting and patient positioning. Therefore, a high dose of radiation can be given without excess damage to normal tissue. SRS can be used to treat only small tumors with well-defined edges. It is most commonly used in the treatment of brain or spinal tumors and brain metastases from other cancer types. For the treatment of some brain metastases, patients may receive radiation therapy to the entire brain (called whole-brain radiation therapy) in addition to SRS.
  SRS requires the use of a head frame or other device to immobilize the patient during treatment to ensure that the high dose of radiation is delivered accurately.
• Stereotactic body radiation therapy: Stereotactic body radiation therapy (SBRT) delivers radiation therapy in fewer sessions, using smaller radiation fields and higher doses than 3D-CRT in most cases. By definition, SBRT treats tumors that lie outside the brain and spinal cord. Because these tumors are more likely to move with the normal motion of the body, and therefore cannot be targeted as accurately as tumors within the brain or spine, SBRT is usually given in more than one dose (8). SBRT can be used to treat only small, isolated tumors, including cancers in the lung and liver (8). Many doctors refer to SBRT systems by their brand names, such as the CyberKnife®.
• Proton therapy: External-beam radiation therapy can be delivered by proton beams as well as the photon beams described above. Protons are a type of charged particle. Proton beams differ from photon beams mainly in the way they deposit energy in living tissue. Whereas photons deposit energy in small packets all along their path through tissue, protons deposit much of their energy at the end of their path (called the Bragg peak) and deposit less energy along the way.
  In theory, use of protons should reduce the exposure of normal tissue to radiation, possibly allowing the delivery of higher doses of radiation to a tumor (9). Proton therapy has not yet been compared with standard external-beam radiation therapy in clinical trials (10, 11).
• Other charged particle beams: Electron beams are used to irradiate superficial tumors, such as skin cancer or tumors near the surface of the body, but they cannot travel very far through tissue (1). Therefore, they cannot treat tumors deep within the body.

Patients can discuss these different methods of radiation therapy with their doctors to see if any is appropriate for their type of cancer and if it is available in their community or through a clinical trial.

Internal radiation therapy
Internal radiation therapy (brachytherapy) is radiation delivered from radiation sources (radioactive materials) placed inside or on the body (12). Several brachytherapy techniques are used in cancer treatment. Interstitial brachytherapy uses a radiation source placed within tumor tissue, such as within a prostate tumor. Intracavitary brachytherapy uses a source placed within a surgical cavity or a body cavity, such as the chest cavity, near a tumor. Episcleral brachytherapy, which is used to treat melanoma inside the eye, uses a source that is attached to the eye.

In brachytherapy, radioactive isotopes are sealed in tiny pellets or “seeds.” These seeds are placed in patients using delivery devices, such as needles, catheters, or some other type of carrier. As the isotopes decay naturally, they give off radiation that damages nearby cancer cells.

If left in place, after a few weeks or months, the isotopes decay completely and no longer give off radiation. The seeds will not cause harm if they are left in the body (see permanent brachytherapy, described below).

Brachytherapy may be able to deliver higher doses of radiation to some cancers than external-beam radiation therapy while causing less damage to normal tissue (1, 12).

Brachytherapy can be given as a low-dose-rate or a high-dose-rate treatment:

• In low-dose-rate treatment, cancer cells receive continuous low-dose radiation from the source over a period of several days (1, 12).
• In high-dose-rate treatment, a robotic machine attached to delivery tubes placed inside the body guides one or more radioactive sources into or near a tumor, and then removes the sources at the end of each treatment session. High-dose-rate treatment can be given in one or more treatment sessions. An example of a high-dose-rate treatment is the MammoSite® system, which is being studied to treat patients with breast cancer who have undergone breast-conserving surgery.

The placement of brachytherapy sources can be temporary or permanent (1, 12):

• For permament brachytherapy, the sources are surgically sealed within the body and left there, even after all of the radiation has been given off. The remaining material (in which the radioactive isotopes were sealed) does not cause any discomfort or harm to the patient. Permanent brachytherapy is a type of low-dose-rate brachytherapy.
• For temporary brachytherapy, tubes (catheters) or other carriers are used to deliver the radiation sources, and both the carriers and the radiation sources are removed after treatment. Temporary brachytherapy can be either low-dose-rate or high-dose-rate treatment.

Doctors can use brachytherapy alone or in addition to external-beam radiation therapy to provide a “boost” of radiation to a tumor while sparing surrounding normal tissue (12).

Systemic radiation therapy
In systemic radiation therapy, a patient swallows or receives an injection of a radioactive substance, such as radioactive iodine or a radioactive substance bound to a monoclonal antibody.

Radioactive iodine (¹³¹I) is a type of systemic radiation therapy commonly used to help treat some types of thyroid cancer. Thyroid cells naturally take up radioactive iodine.

For systemic radiation therapy for some other types of cancer, a monoclonal antibody helps target the radioactive substance to the right place. The antibody joined to the radioactive substance travels through the blood, locating and killing tumor cells. For example:

• The drug ibritumomab tiuxetan (Zevalin®) has been approved by the Food and Drug Administration (FDA) for the treatment of certain types of B-cell non-Hodgkin lymphoma (NHL). The antibody part of this drug recognizes and binds to a protein found on the surface of B lymphocytes.
• The combination drug regimen of tositumomab and iodine I 131 tositumomab (Bexxar®) has been approved for the treatment of certain types of NHL. In this regimen, nonradioactive tositumomab antibodies are given to patients first, followed by treatment with tositumomab antibodies that have ¹³¹I attached. Tositumomab recognizes and binds to the same protein on B lymphocytes as ibritumomab. The nonradioactive form of the antibody helps protect normal B lymphocytes from being damaged by radiation from ¹³¹I.

Many other systemic radiation therapy drugs are in clinical trials for different cancer types.
Some systemic radiation therapy drugs relieve pain from cancer that has spread to the bone (bone metastases). This is a type of palliative radiation therapy. The radioactive drugs samarium-153-lexidronam (Quadramet®) and strontium-89 chloride (Metastron®) are examples of radiopharmaceuticals used to treat pain from bone metastases (13).

Why are some types of radiation therapy given in many small doses?

Patients who receive most types of external-beam radiation therapy usually have to travel to the hospital or an outpatient facility up to 5 days a week for several weeks. One dose (a single fraction) of the total planned dose of radiation is given each day. Occasionally, two treatments a day are given.
Most types of external-beam radiation therapy are given in once-daily fractions. There are two main reasons for once-daily treatment:

• To minimize the damage to normal tissue.
• To increase the likelihood that cancer cells are exposed to radiation at the points in the cell cycle when they are most vulnerable to DNA damage (1, 14).

In recent decades, doctors have tested whether other fractionation schedules are helpful (1), including:

• Accelerated fractionation—treatment given in larger daily or weekly doses to reduce the number of weeks of treatment.
• Hyperfractionation—smaller doses of radiation given more than once a day.
• Hypofractionation—larger doses given once a day or less often to reduce the number of treatments.

Researchers hope that different types of treatment fractionation may either be more effective than traditional fractionation or be as effective but more convenient.

When will a patient get radiation therapy?

A patient may receive radiation therapy before, during, or after surgery. Some patients may receive radiation therapy alone, without surgery or other treatments. Some patients may receive radiation therapy and chemotherapy at the same time. The timing of radiation therapy depends on the type of cancer being treated and the goal of treatment (cure or palliation).

Radiation therapy given before surgery is called pre-operative or neoadjuvant radiation. Neoadjuvant radiation may be given to shrink a tumor so it can be removed by surgery and be less likely to return after surgery (1).

Radiation therapy given during surgery is called intraoperative radiation therapy (IORT). IORT can be external-beam radiation therapy (with photons or electrons) or brachytherapy. When radiation is given during surgery, nearby normal tissues can be physically shielded from radiation exposure (15). IORT is sometimes used when normal structures are too close to a tumor to allow the use of external-beam radiation therapy.

Radiation therapy given after surgery is called post-operative or adjuvant radiation therapy.

Radiation therapy given after some types of complicated surgery (especially in the abdomen or pelvis) may produce too many side effects; therefore, it may be safer if given before surgery in these cases (1).

The combination of chemotherapy and radiation therapy given at the same time is sometimes called chemoradiation or radiochemotherapy. For some types of cancer, the combination of chemotherapy and radiation therapy may kill more cancer cells (increasing the likelihood of a cure), but it can also cause more side effects (1, 14).

After cancer treatment, patients receive regular follow-up care from their oncologists to monitor their health and to check for possible cancer recurrence. Detailed information about follow-up care can be found at NCI's Follow-up Medical Care page.

Does radiation therapy make a patient radioactive?

External-beam radiation does not make a patient radioactive.
During temporary brachytherapy treatments, while the radioactive material is inside the body, the patient is radioactive; however, as soon as the material is removed, the patient is no longer radioactive. For temporary brachytherapy, the patient will usually stay in the hospital in a special room that shields other people from the radiation.

During permanent brachytherapy, the implanted material will be radioactive for several days, weeks, or months after the radiation source is put in place. During this time, the patient is radioactive. However, the amount of radiation reaching the surface of the skin is usually very low. Nonetheless, this radiation can be detected by radiation monitors and contact with pregnant woman and young children may be restricted for a few days or weeks.

Some types of systemic radiation therapy may temporarily make a patient’s bodily fluids (such as saliva, urine, sweat, or stool) emit a low level of radiation. Patients receiving systemic radiation therapy may need to limit their contact with other people during this time, and especially avoid contact with children younger than 18 and pregnant women.
A patient’s doctor or nurse will provide more information to family members and caretakers if any of these special precautions are needed. Over time (usually days or weeks), the radioactive material retained within the body will break down so that no radiation can be measured outside the patient’s body.

What are the potential side effects of radiation therapy?

Radiation therapy can cause both early (acute) and late (chronic) side effects. Acute side effects occur during treatment, and chronic side effects occur months or even years after treatment ends (1). The side effects that develop depend on the area of the body being treated, the dose given per day, the total dose given, the patient’s general medical condition, and other treatments given at the same time.
Acute radiation side effects are caused by damage to rapidly dividing normal cells in the area being treated. These effects include skin irritation or damage at regions exposed to the radiation beams. Examples include damage to the salivary glands or hair loss when the head or neck area is treated, or urinary problems when the lower abdomen is treated.

Most acute effects disappear after treatment ends, though some (like salivary gland damage) can be permanent. The drug amifostine (Ethyol®) can help protect the salivary glands from radiation damage if it is given during treatment. Amifostine is the only drug approved by the FDA to protect normal tissues from radiation during treatment. This type of drug is called a radioprotector. Other potential radioprotectors are being tested in clinical trials.

Fatigue is a common side effect of radiation therapy regardless of which part of the body is treated. Nausea with or without vomiting is common when the abdomen is treated and occurs sometimes when the brain is treated. Medications are available to help prevent or treat nausea and vomiting during treatment.
Late side effects of radiation therapy may or may not occur. Depending on the area of the body treated, late side effects can include (1):

• Fibrosis (the replacement of normal tissue with scar tissue, leading to restricted movement of the affected area).
• Damage to the bowels, causing diarrhea and bleeding.
• Memory loss.
• Infertility (inability to have a child).
• Rarely, a second cancer caused by radiation exposure.

Second cancers that develop after radiation therapy depend on the part of the body that was treated (16). For example, girls treated with radiation to the chest for Hodgkin lymphoma have an increased risk of developing breast cancer later in life. In general, the lifetime risk of a second cancer is highest in people treated for cancer as children or adolescents (16).
Whether or not a patient experiences late side effects depends on other aspects of their cancer treatment in addition to radiation therapy, as well as their individual risk factors. Some chemotherapy drugs, genetic risk factors, and lifestyle factors (such as smoking) can also increase the risk of late side effects.
When suggesting radiation therapy as part of a patient’s cancer treatment, the radiation oncologist will carefully weigh the known risks of treatment against the potential benefits for each patient (including relief of symptoms, shrinking a tumor, or potential cure). The results of hundreds of clinical trials and doctors’ individual experiences help radiation oncologists decide which patients are likely to benefit from radiation therapy.
A more comprehensive discussion of acute and late side effects from radiation therapy, as well as ways to cope with these side effects, can be found in the NCI publications Radiation Therapy and You: Support for People With Cancer and the Radiation Therapy Side Effects Series.

What research is being done to improve radiation therapy?

Doctors and other scientists are conducting research studies called clinical trials to learn how to use radiation therapy to treat cancer more safely and effectively. Clinical trials allow researchers to examine the effectiveness of new treatments in comparison with standard ones, as well as to compare the side effects of the treatments.

Researchers are working on improving image-guided radiation so that it provides real-time imaging of the tumor target during treatment. Real-time imaging could help compensate for normal movement of the internal organs from breathing and for changes in tumor size during treatment.

Researchers are also studying radiosensitizers and radioprotectors, chemicals that modify a cell's response to radiation:

• Radiosensitizers are drugs that make cancer cells more sensitive to the effects of radiation therapy. Several agents are under study as radiosensitizers. In addition, some anticancer drugs, such as 5-fluorouracil and cisplatin, make cancer cells more sensitive to radiation therapy.
• Radioprotectors (also called radioprotectants) are drugs that protect normal cells from damage caused by radiation therapy. These drugs promote the repair of normal cells exposed to radiation. Many agents are currently being studied as potential radioprotectors.

The use of carbon ion beams in radiation therapy is being investigated by researchers, but, at this time, the use of these beams remains experimental. Carbon ion beams are available at only a few medical centers around the world. They are not currently available in the United States. Researchers hope that carbon ion beams may be effective in treating some tumors that are resistant to traditional radiation therapy.

People with cancer who are interested in taking part in a clinical trial should talk with their doctor. A comprehensive list of current clinical trials is available on NCI’s website.
NCI's Cancer Information Service (CIS) can also provide information about clinical trials and help with clinical trial searches. Call the CIS at 1–800–4–CANCER (1–800–422–6237).

Selected References

1. Lawrence TS, Ten Haken RK, Giaccia A. Principles of Radiation Oncology. In: DeVita VT Jr., Lawrence TS, Rosenberg SA, editors. Cancer: Principles and Practice of Oncology. 8^th ed. Philadelphia: Lippincott Williams and Wilkins, 2008.
2. Taylor A, Powell ME. Intensity-modulated radiotherapy—what is it? Cancer Imaging 2004; 4(2):68–73. [PubMed Abstract]
3. Gaspar LE, Ding M. A review of intensity-modulated radiation therapy. Current Oncology Reports 2008; 10(4):294–299. [PubMed Abstract]
4. Veldeman L, Madani I, Hulstaert F. et al. Evidence behind use of intensity-modulated radiotherapy: A systematic review of comparative clinical studies. Lancet Oncology 2008; 9(4):367–375. Erratum in: Lancet Oncology 2008; 9(6):513. [PubMed Abstract]
5. Noda SE, Lautenschlaeger T, Siedow MR, et al. Technological advances in radiation oncology for central nervous system tumors. Seminars in Radiation Oncology 2009; 19(3):179–186. [PubMed Abstract]
6. Detorie NA. Helical tomotherapy: A new tool for radiation therapy. Journal of the American College of Radiology 2008; 5(1):63–66.
7. Fenwick JD, Tomé WA, Soisson ET, et al. Tomotherapy and other innovative IMRT delivery systems. Seminars in Radiation Oncology 2006; 16(4):199–208. [PubMed Abstract]
8. Kavanagh BD, Timmerman RD. Stereotactic radiosurgery and stereotactic body radiation therapy: An overview of technical considerations and clinical applications. Hematology/Oncology Clinics of North America 2006; 20(1):87–95. [PubMed Abstract]
9. Schulz-Ertner D, Jäkel O, Schlegel W. Radiation therapy with charged particles. Seminars in Radiation Oncology 2006; 16(4):249–259. [PubMed Abstract]
10. Brada M, Pijls-Johannesma M, De Ruysscher D. Proton therapy in clinical practice: Current clinical evidence. Journal of Clinical Oncology 2007; 25(8):965–970.
11. Olsen DR, Bruland OS, Frykholm G, Norderhaug, IN. Proton therapy—a systematic review of clinical effectiveness. Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology 2007; 83(2):123–132. [PubMed Abstract]
12. Patel RR, Arthur DW. The emergence of advanced brachytherapy techniques for common malignancies. Hematology/Oncology Clinics of North America 2006; 20(1):97–118. [PubMed Abstract]
13. Lam MG, de Klerk JM, van Rijk PP, Zonnenberg, BA. Bone seeking radiopharmaceuticals for palliation of pain in cancer patients with osseous metastases. Anti-cancer Agents in Medicinal Chemistry 2007; 7(4):381–397. [PubMed Abstract]
14. Connell PP, Hellman S. Advances in radiotherapy and implications for the next century: A historical perspective. Cancer Research 2009; 69(2):383–392.
15. Calvo FA, Meirino RM, Orecchia R. Intraoperative radiation therapy first part: Rationale and techniques. Critical Reviews in Oncology/Hematology 2006; 59(2):106–115. [PubMed Abstract]
16. Travis LB, Hodgson D, Allan JM, Van Leeuwen FE. Second Cancers. In: DeVita VT Jr., Lawrence TS, Rosenberg SA, editors. Cancer: Principles and Practice of Oncology. 8th ed. Philadelphia: Lippincott Williams and Wilkins, 2008.

Related Resources

• Radiation Therapy and You: Support for People With Cancer
• Radiation Therapy to Treat Cancer

• Reviewed: June 30, 2010

Most text on the National Cancer Institute website may be reproduced or reused freely. The National Cancer Institute should be credited as the source and a link to this page included, e.g., “Radiation Therapy for Cancer was originally published by the National Cancer Institute.”

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Radiation Therapy Side Effect Series has practical steps and advice to help you manage nine (9) side effects from radiation therapy, so you feel better during treatment:

• Diarrhea (PDF)
• Fatigue (PDF)
• Hair loss (PDF)
• Mouth and throat changes (PDF)
• Nausea and vomiting (PDF)
• Sexuality and fertility in men (PDF)
• Sexuality and fertility in women (PDF)
• Skin changes (PDF)
• Urination changes (PDF)

These colorful sheets are designed to help you learn how to manage these side effects. They include engaging quotes and questions to ask your health care provider, so you can learn more. Health conditions that may need urgent medical care are highlighted.

how your digestive system works

How long does it take to digest food — from the time you eat it to the time you excrete it? 
The digestion process takes between 24 and 72 hours, Elimination of undigested residue food  usually begins after 24 hours. Complete elimination from the body may take several days. 

Answers from Michael F. Picco, M.D.
Digestion time varies between individuals and between men and women. After you eat, it takes about six to eight hours for food to pass through your stomach and small intestine. Food then enters your large intestine (colon) for further digestion, absorption of water and, finally, elimination of undigested food.

In the 1980s, Mayo Clinic researchers measured digestion time in 21 healthy people. Total transit time, from eating to elimination in stool, averaged 53 hours (although that figure is a little overstated, because the markers used by the researchers passed more slowly through the stomach than actual food). The average transit time through just the large intestine (colon) was 40 hours, with significant difference between men and women: 33 hours for men, 47 hours for women.

Two British doctors studied digestion time in children. They fed 35 children juice containing a red marker and asked the children's mothers to note when the stool first turned red. The mean time of transit from mouth to anus for the group was 33 hours (meaning half the children had digestion times slower than this and half had digestion times greater than this).

With Regards,
Michael F. Picco, M.D.




Your digestive system gears up
A fresh-baked apple pie has just come out of the oven. Just the sight and smell of it are enough to make you start salivating. So even before you take a bite, your digestive system has swung into action.

After the first morsel enters your mouth, the many organs of your digestive tract kick into high gear. Here's a look at how your digestive system works, from top to bottom.



Mouth and salivary glands
After you take your first bite of pie, your salivary glands produce saliva — a mixture of secretions that help lubricate and break down food. Besides the salivary glands in the lining of your mouth, you have three pairs of larger salivary glands — the parotid, sublingual and submandibular glands. You typically produce about 2 pints (about 1 liter) of saliva a day.

Not all of the work is chemical, though. As you savor the bite of pie, your teeth work to break down the pie while your tongue mixes it with saliva. This action transforms it into a soft, moist, rounded mass (bolus) suitable for swallowing.



Esophagus
As you swallow the bite of pie, muscles in your mouth and throat propel it to your upper esophagus, the tube that connects your throat to your stomach. Muscles in the wall of your esophagus create synchronized waves — one after another — that propel the pie into your stomach. In this process, called peristalsis, muscles behind the bolus of pie contract, squeezing it forward, while muscles ahead of it relax, allowing it to advance without resistance.

When the bolus reaches the lower end of your esophagus, pressure from the food signals a muscular valve — the lower esophageal sphincter — to relax and let the food enter your stomach.



Stomach
After entering your stomach, the pie is broken down further. With its powerful muscles, the stomach begins churning and mixing the food into smaller and smaller pieces. Your digestive glands in your stomach lining produce stomach acid and enzymes, which mix with the food to form a murky semifluid or paste called chyme.

Once the chyme is well-mixed, waves of muscle contractions propel it through a valve called the pylorus and into the first section of your small intestine (duodenum). The pylorus might release about an eighth of an ounce (about 4 milliliters) of chyme at a time. The rest is held back for more mixing.



Pancreas, liver and gallbladder
In your duodenum, digestion continues as chyme from the stomach mixes with a variety of digestive juices from your pancreas, liver and gallbladder:

Pancreas. The pancreas produces digestive enzymes that help break down proteins, carbohydrates and fats.

Liver. The liver produces bile, a solution that helps you digest fats.

Gallbladder. The gallbladder stores bile. As fatty food enters the upper portion of your small intestine (the duodenum), the gallbladder squeezes bile into the small intestine through the bile ducts.



Small intestine
As bile and pancreatic digestive juices mix with other juices secreted by the wall of your small intestine, digestion continues. What was once apple pie is propelled into the second portion of your small intestine, the jejunum. Here it's further broken down into smaller molecules of nutrients that can be absorbed. Then it moves into the final and longest portion of your small intestine — the ileum — where virtually all of the remaining nutrients are absorbed through the lining of the ileum's wall.

What remains of the food when it reaches the end of the ileum is a combination of water, electrolytes — such as sodium and chloride — and waste products, such as plant fiber and dead cells shed from the lining of your digestive tract.



Large intestine
As this residue passes through the colon, nearly all of the water is absorbed, leaving a usually soft but formed substance called stool. Muscles in the wall of your colon separate the waste into small segments that are pushed into your lower colon and rectum. As the rectal walls are stretched, they signal the need for a bowel movement.

When the sphincter muscles in your anus relax, the rectal walls contract to increase pressure. These coordinated muscle contractions expel the stool.

The End of Slide Show. 

Water Cure Acid Reflux/Heartburn

Subject: Re: Maher Hakim Testomonial 
Date: Sun, 10 Oct 2010 17:07:43 +0400 
From: Maher Hakim  
To: Robert Butts

About 3 months back I had a sever heart burn at 4 am which I thought it was a heart attack. After very panicky night/morning I stated to feel sever pain when I sleep on either side or even when I lay on my back, the pain was hard along with some sort of a shiver and massive bloating and bleaches. I lost my ability to sleep even though I have tried all possible solutions (PPI, Anti Acid, Raise the bed…etc) but nothing can stop the pain. I did an endoscopy and I was diagnosed with a small hernia, a small esophagus diverticulium and some bacteria in the stomach (h. Pylori). 

I was given more PPI and a lot of antibiotics for about 30 days. My sleep problem grow worse to a full fledge PSYCHOLOGICAL INSOMNIA (fear of sleeping) and I was diagnosed by my psychiatrist with sever anxiety and put me on 3 different medications (with horrible possible side effects). My over all health has deteriorated because of sever the anxiety that was coming from the fact that I cannot sleep at night without the help of drugs and I was over worried about my family well-being ( a lovely wife and 2 children) in case I die. Of course before all this started I did not have fear of sleep nor fear of death. 

After seeing many top notch doctors and after I have done a lot of research on the internet and have reached the conclusion that I have a serious case of systemic candidas because of the frequent use of antibiotics. But however now my serious insomnia along with the 3 heavy PSYCHOLOGICAL drugs made me feel like a zombie with few days left to live. Boy it is sure a horrible and helpless feeling.

Today I was on the internet and read about the water cure (which by the way it should be renamed to "The water and sea salt cure") and I have reached out to my sea salt and put 1/4 teaspoon in a large glass of pure water and drank…. and WOW immediately my body pains decreased and my overall mental zombie mode improved from depression and fear to a bit more normal and more positive mind set, which have made me feel good enough to write this testimonial.

So I will continue with the Sea Salt & Water regimen and will keep you updated on my improvement.

Keep up the great work and god bless those who truly give and not desire to be mere takers. 

Kind Regards,
Maher Hakim

Dehydration Causes, Symptoms and Tips to Stay Hydrated

Our Body of Water
The majority of the body is made up of water with up to 75% of the
body's weight due to H2O. Most of the water is found within the
cells of the body (intracellular space). The rest is found in the
extracellular space, which consists of the blood vessels
(intravascular space) and the spaces between cells (interstitial
space).

What is Dehydration?
Dehydration occurs when the amount of water leaving the body is
greater than the amount being taken in. The body is very dynamic
and always changing. This is especially true with water levels in
the body. We lose water routinely when we: 
>breathe and humidified air leaves the body; 
>sweat to cool the body; and
>urinate or have a bowel movement to rid the body of waste
products.

In a normal day, a person has to drink a significant amount of
water to replace this routine loss.

Causes of Dehydration: Diarrhea.
Diarrhea is the most common reason a person loses excess
water. Diarrhea consists of unusually frequent or unusually liquid
bowel movements and excessive watery evacuations of fecal material. Persistent diarrhea is both uncomfortable and dangerous, as a significant amount of water can be lost with each
bowel movement. Worldwide, more than four million children die
each year because of dehydration from diarrhea.



Causes of Dehydration: Vomiting
Vomiting is the act of forcible emptying of the stomach, in which
the stomach has to overcome the pressures that are normally in
place to keep food and secretions within the stomach. The
stomach almost turns itself inside out - forcing itself into the
lower portion of the esophagus (the tube that connects the mouth
to the stomach) during a vomiting episode. Constant vomiting can
be a serious cause of fluid loss and it is difficult for a person to
replace water if they are unable to tolerate liquids.



Causes of Dehydration: Sweat
The body can lose significant amounts of water when it tries to
cool itself by sweating. Whether the body is hot because of the
environment (for example, working in a warm environment),
intense exercising in a hot environment, or because a fever is
present due to an infection; the body uses a significant amount of
water in the form of sweat to cool itself. Depending upon weather
conditions, a brisk walk will generate up to 16 ounces of sweat
(one pound of water).



Causes of Dehydration: Diabetes
In people with diabetes, elevated blood sugar levels cause sugar
to spill into the urine, and water then follows, which can cause
significant dehydration. For this reason, frequent urination and
excessive thirst are among the symptoms of diabetes.



Causes of Dehydration: Burns
The skin has an important role to play in the fluid and temperature
regulation of the body. If enough skin area is injured, the ability to maintain that control can be lost. Burn victims become
dehydrated because water seeps into the damaged skin. Other
inflammatory diseases of the skin are also associated with fluid
loss.



Causes of Dehydration: Inability to Drink Fluids
The inability to drink adequately is another potential cause of
dehydration. Whether it is the lack of availability of water or the
lack of strength to drink adequate amounts, this, coupled with
routine or excessive amounts of water loss can compound the
degree of dehydration.



What Are the Signs and Symptoms of Dehydration?

The body's initial responses to dehydration are thirst to increase
water intake along with decreased urine output to try to conserve
water. The urine will become concentrated and more yellow in
color. As the level of water loss increases, more symptoms can
become apparent, such as increased thirst, dry mouth, cessation
of tear production by the eyes, cessation of sweating , muscle
cramps, nausea and vomiting, heart palpitations, and
lightheadedness (especially when standing). With severe
dehydration, confusion and weakness will occur as the brain and
other body organs receive less blood. Finally, coma and organ
failure will occur if the dehydration remains untreated.



How is Dehydration Diagnosed?
Dehydration is often a clinical diagnosis. Aside from diagnosing
the reason for dehydration, the health care professional's
examination of the patient will assess the level of dehydration.
Initial evaluations may include:
Mental status tests to evaluate whether the patient is awake,
alert, and oriented.
Vital sign assessments may include postural readings
(blood pressure and pulse rate are taken lying down and
standing). With dehydration, the pulse rate may increase and
the blood pressure may drop because the intravascular
space is depleted of water.
Temperature may be measured to assess fever.
Skin will be checked to see if sweat is present and to assess
the degree of elasticity. As dehydration progresses, the skin
loses its water content and becomes less elastic.
Infant evaluation: infants may have additional evaluations
performed, including checking for a soft spot on the skull
(sunken fontanelle), assessing the suck mechanism, muscle,tone, or loss of sweat in the armpits and groin.

Pediatric patients are often weighed during routine visits, thus a body weight measurement may be helpful in assessing how much water has been lost with the acute illness.
In some cases, blood tests to measure potential electrolyte abnormalities and urinalysis may be ordered to determine the level of dehydration in the patient.



How is Dehydration Treated?

Fluid replacement is the treatment for dehydration. This may be
attempted by replacing fluid by mouth, but if this fails, intravenous
fluid (IV) may be required. Should oral rehydration be attempted,
frequent small amounts of clear fluids should be used. 

Clear fluids include:

>water,
>clear broths,
>popsicles,
>Jell-O, and
>other replacement fluids that may contain electrolytes.

Can Dehydration Be Treated at Home?
Dehydration occurs over time. If it can be recognized in its earliest
stages, and if its cause can be addressed, then home treatment may be adequate. Steps a person can take at home to prevent
severe dehydration include:

>People with vomiting and diarrhea can try to alter their diet
and use water-cure-protocol formula to control symptoms to minimize water loss.

>Acetaminophen or ibuprofen may be used to control fever.
Ibuprofen may irritate the stomach and cause nausea and
vomiting, so it should be used with caution in individuals
who already have these symptoms.

>Fluid replacements may be attempted by replacing fluid by mouth with frequent small amounts of clear fluids.

 If the individual becomes confused or lethargic; if there is
persistent, uncontrolled fever, vomiting, or diarrhea; or if there are
any other specific concerns, then medical care should be accessed. EMS or 911 should be activated for any person with altered mental status.



What Are the Complications of Dehydration?

Complications of dehydration may occur because of the
dehydration, and/or because of the underlying disease or situation
that causes the fluid loss. Complications that may occur include:
>kidney failure,

>coma,

>shock,

>heat-related illnesses (heat exhaustion or heat stroke), and

>electrolyte abnormalities.



Dehydration Prevention Tip #1

Plan ahead and take extra water to all outdoor events where
increased sweating, activity, and heat stress will increase fluid
loss. Encourage athletes and people who work outside to replace
fluids at a rate that equals the loss.



Dehydration Prevention Tip #2

Check weather forecasts for high heat index days. When
temperatures are high, avoid exercise, outdoor exposure, and plan
events that must occur outside during times of the day when
temperatures are lower.



Dehydration Prevention Tip #3

The young and elderly are most at risk of dehydration. Ensure that
older people, infants, and children have adequate drinking water or
fluids available and assist them as necessary. Encourage
individuals who are incapacitated or impaired to drink plenty of
water and assure they are provided with adequate fluids.
During heat waves, attempts should be made to check on the elderly in their homes. During the Chicago heat wave of 1995, more than 600 people died in their homes from heat exposure.



Dehydration Prevention Tip #4

Avoid alcohol consumption, especially when it is very hot, because
alcohol increases water loss and impairs your ability to recognize
early signs associated with dehydration. 



Dehydration Prevention Tip #5

Wear light-colored and loose-fitting clothing if you must be
outdoors when it is hot outside. Drink plenty of water and carry a
personal fan or mister to cool yourself.



Dehydration Prevention Tip #6

Break up your exposure to hot temperatures. Find air-conditioned
or shady areas and allow yourself to cool between exposures.
Taking someone into a cooled area for even a couple of hours
each day will help prevent the cumulative effects of high heat
exposure.



Dehydration Prevention Tip #7

Know the signs and symptoms of heat cramps, heat rash, heat
exhaustion, and heat stroke. Preventing dehydration is one step to
avoid these conditions.



Dehydration At A Glance

>The body needs water to function.

>Dehydration occurs when water intake is less than water loss.

>Symptoms range from mild to life-threatening.

>Prevention is the important first step in treating dehydration.

>The young and the elderly are especially susceptible to
dehydration.

How is dehydration diagnosed?

Dehydration is often a clinical diagnosis. Aside from diagnosing the reason for dehydration, the health care professional's examination of the patient will assess the level of dehydration. Initial evaluations may include:

Mental status tests to evaluate whether the patient is awake, alert, and oriented. Infants and children may appear listless and have whiny cries and decreased muscle tone.


Vital signs may include postural readings (blood pressure and pulse rate are taken lying down and standing). With dehydration, the pulse rate may increase and the blood pressure may drop because the blood is depleted of fluid. People taking beta blocker medications for high blood pressure, heart disease, or other indications, occasionally lose the ability to increase their heart rate as a compensation mechanism since these medications block the adrenaline receptors in the body.

Temperature may be measured to assess fever. While it is common to measure temperature in the ear (tympanic) or by mouth (orally), a rectal thermometer may be used to assess core body temperature if the patient appears warm, but no fever is noted tympanically or orally.

Skin may be checked to see if sweat is present and to assess the degree of elasticity (turgor). As dehydration progresses, the skin loses its water content and becomes less elastic. The amount of sweat is often felt in the armpit or groin, two areas that tend to have moisture normally.

The mouth can become dry and the health care professional may look at or feel the tongue to see how wet it is.

Infants may have additional evaluations performed, including checking for a soft spot on the skull (sunken fontanelle), and assessing the suck mechanism, loss of sweat in the armpits and groin, and muscle tone. All are signs of potential significant dehydration.

Pediatric patients are often weighed during routine child visits, thus a body weight measurement may be helpful in assessing how much water has been lost with the acute illness. This is very rough estimate because all scales are not the same, and for infants and children, it is important to know what clothing they were wearing when the original weight was taken.

Laboratory testing

The purpose of blood tests is to assess potential electrolyte abnormalities (including sodium, potassium, chloride, and carbon dioxide levels) associated with the dehydration. Other tests may or may not be ordered depending upon the underlying cause of dehydration, the severity of illness, and the health care professional's assessment of their needs and resources available.

Other blood tests may be helpful in determining the level of dehydration. Hemoglobin and red blood cell counts may be elevated because the blood is more concentrated with water loss from the intravascular space.

Kidney function tests including BUN and creatinine may be elevated, and this is one way of measuring the severity of dehydration.

Urinalysis may be ordered to determine urine concentration; the more concentrated the urine, the more dehydrated the patient.

Many of the Major Pains of the Body ...

...denote localized thirst. Heartburn in the upper parts of the intestinal tract, and colitis pain and its companion constipation in the lower intestinal tact --- which predispose to cancers of stomach, esophagus, colon, rectum,and their pancreatic water-distributing organ --- are the most frequently seen thirst pains of the body. 

The pancreas is responsible for giving priority to the intestinal tract for its water-distribution mechanisms. Primarily, it manufactures of  a watery bicarbonate solution and injects it into the first part of the small intestine. Not only does this alkaline, enzyme-laden watery solution neutralize the acid from the stomach, but it also constantly irrigates the intestinal walls during the digestive process, As it was explained, its rate of insulin production is dependent on the amount of water that reaches the pancreas.

When the body gets more and more dehydrated,...


... insulin release is reduced until full-blown diabetes develops. With unintegrated insulin release and without considering the body's state of hydration, much water also leaves the blood along with the sugar that enters all cells of the body through their insulin receptor openings. Such an uncontrolled loss of water from blood circulation, in a dehydrated state, limits the amount of water that reaches the brain, and that is a no-no for the integrity of brain function.