Thoracic Oncology

Thoracic Oncology

 

PET Imaging of Esophageal Cancer

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Course Video Transcript

Good morning.

 

My name is Ka Kit Wong.

 

I'm a Nuclear Medicine Physician at the University of Michigan.

 

We're going to be going through PET/CT imaging of esophageal cancer.

 

The objectives of the talk are to appreciate the diagnosis,

 

staging, work up, and management of esophageal cancer.

 

To describe typical FDG PET CT findings of the primary tumor, regional,

 

and distant metastases.

 

To review indications and test performance of FDG PET CT for staging and

 

restaging compared to standard anatomic imaging, CT and endoscopic ultrasound.

 

A question, which of the following statements regarding

 

FDG PET/CT imaging of esophageal cancer is true?

 

A) PET/CT has a high great than 90% sensitive for

 

detecting T1 and T2 primary esophageal cancers.

 

B) The introduction of PET/CT for preoperative staging has made CT and

 

endoscopic ultrasound obsolete.

 

C) PET/CT has superior specificity than CT and

 

endoscopic ultrasound for staging of regional nodal metastases.

 

And D) PET/CT performs poorly for detecting distant metastases to bone.

 

Esophageal cancer is a rare tumor.

 

10% of all gastrointestinal malignancies with a poor 5-year

 

survival between 14 to 20%.

 

Squamous cell cancer accounts for 50-70% and adenocarcinoma 30-50% of all cancers.

 

Squamous cell cancer affects the middle and distal thirds.

 

And alcohol and smoking are risk factors.

 

Adenocarcinoma is becoming more common in a fixed distal part and

 

this is associated with Barrett's esophagus.

 

Only 15% of esophageal cancers are proximal third tumors.

 

The esophagus does not have serosa therefore infiltration into

 

the mediastinum occurs early.

 

The esophagus is lymphatic- and vascular-rich; therefore,

 

it is prone to early nodal and distant metastatic disease.

 

Distant sites are the liver, adrenal, lung, and

 

bone, with spread at diagnosis of 20 to 30% of cases.

 

Early stage disease is often asymptomatic.

 

However, late stage disease presents with dysphagia due to obstruction.

 

Staging of esophageal cancer follows the American Joint Committee on

 

Cancer's Seventh Edition TNM staging system.

 

The seventh edition defines regional nodes to the level of the celiac axis.

 

The number of disease nodes may be more important for

 

prognosis rather than the actual sites of these nodes.

 

This is example of the T-staging system.

 

A TX score is when the primary tumor cannot be assessed.

 

Very early, small tumors are T1.

 

T1b, invading the submucosa.

 

And large, invasive tumors are T4.

 

Being T4a, resectable, or T4b, unresectable.

 

In terms of an N stage, when you have N0,

 

there's no evidence of regional lymph node metastases.

 

And then you can have N1, N2, or N3 disease,

 

depending on the number of lymph nodes.

 

The individual T, N, and M scores are combined to reach a stage

 

one to four with four being the presence of distenmastate disease.

 

54 to 69% of patients are eligible for surgery.

 

The main survival after surgery however is only 13%-19%.

 

Neoadjuvant chemotherapy and

 

external beam radiation therapy prior to operation is gaining acceptance.

 

Conventional work-up is fluoroscopy, CT, MRI, endoscopic ultrasound.

 

PET/CT, positron emission tomography with hybrid CT Using

 

18F-fluorodeoxyglucose is a relatively new imaging modality.

 

Adenocarcinoma and

 

squamous cell carcinomas have overall similar metabolic signatures.

 

Adenocarcinomas mucinous types near the gastro-esophageal

 

junction may have slightly less FDG uptake than squamous cell cancers.

 

The majority though not all literature support the intensity of FDG uptake is

 

correlated to survival.

 

FDG uptake is a prognostic indicator.

 

Primary tumor SUVs of less than 3.0 have better survival.

 

Prognostic indicators such as the length of tumor, number of N1 positive

 

lymph nodes and distant FDG-avid sites also predict a lower survival.

 

Indications for PET/CT include a strategy to detect distant metastases at diagnosis.

 

Improving the specificity of lymph node staging, combining PET/CT and endoscopic

 

ultrasound guided biopsy as a preoperative workup for the highest nodal yield.

 

PET/CT Performance.

 

For locoregional staging,

 

PET/CT has a sensitivity of 51% and a specificity of 94%.

 

For distance staging, it has a sensitivity of 67% and a specificity of 84%.

 

For the primary tumor, PET CT has overall sensitivity of 80% for

 

primary esophageal cancer.

 

The sensitivity is close to a 100% for large tumors T3 and

 

T4 but the sensitivity is only 43% for smaller T1 tumors.

 

PET/CT cannot detect inside you or T1a tumors.

 

PET/CT cannot determine the T stage of an esophageal cancer.

 

This is a PET/CT scan, which shows intense FDG outtake in the distill esophagus.

 

The fusion FDG PET/CT images, show that it's localized to the distill esophagus.

 

This image shows the PET on the top and the fusion PET/CT on the bottom.

 

There are FDG avid long nodules compatible with nodal metastatic disease.

 

This is a different case.

 

There is intensive FDG uptake which localizes to the upper

 

cervical esophagus with circumferential mucosal thickening.

 

This is compatible with a cervical esophageal cancer.

 

This PET image shows EDG outtake in prevascular lymph node.

 

This is compatible with nodal metastatic disease.

 

This actual image shows FDG uptake in a lung nodule in the right middle lobe.

 

This is compatible with lung metastasis.

 

Some pitfalls of FDG PET/CT are that mild esophageal uptake

 

with an SUV max of less than four may actually related to esophagitis or

 

lower esophageal sphincter activity.

 

Hiatal hernias, benign stricture after dilatations, post-biopsy and

 

esophageal leiomyomas can have mild FDG uptake.

 

These are sources of false-positive results.

 

Small intracapsular nodal metastases have a high false-negative rate.

 

Intense uptake in the primary tumor may obscure subtle abnormal adjacent nodes.

 

Synchronous primary neoplasms are found in 5.5 to 8% of patients for

 

esophageal cancer on PET scanning.

 

PET/CT compared to CT and endoscopic ultrasound combination for

 

nodal staging shows that PET although being less sensitive,

 

22%, has a very high specificity of 91% compared to CT/EUS,

 

83% sensitivity but only 45% specificity.

 

Therefore, the combination of PET CT and

 

CT/EUS would have the highest diagnostic accuracy.

 

PET/CT versus CT for distant MI disease.

 

The PET scan has a sensitivity of 69% and a specificity of 93%.

 

Whereas the CT has only a sensitivity of 46% and the lowest specificity of 74%.

 

In PET/CT adverse to CT for M1 bone disease.

 

The PET has a sensitivity of 92% and a specificity of 94%,

 

which is superior to CT of 77% and specificity of 84%.

 

This is a case showing FDG avid bone metastasis and

 

the arrow is localizing lumber's fine bone metastasis in this

 

patient with esophageal cancer.

 

These axial images show FDG [INAUDIBLE] rib metastases.

 

This image in the same patient show FDG avid bone metastases

 

to the right pubic synthesis and the left femoral head.

 

The impact of PET/CT on patient management is that it will change

 

staging in 14% of patients.

 

PET will find distant metastatic diseases in additional 5 to 8%

 

of patients after conventional imaging workup.

 

PET is insensitive for locoregional disease and

 

does not replace CT/endoscopic ultra sound for detection of neural disease.

 

PET is more specific than CT/endoscopic ultra sound for regional and

 

distant disease.

 

Using PET/CT for detection of recurrences two-thirds

 

of patients relapse within one to two years after their diagnosis.

 

For re-staging PET/CT has been shown to have a sensitivity of 94% and

 

a specificity of 82% for detection of recurrent metastatic disease.

 

PET is not really better than the conventional modality CT and MRI.

 

PERCIST is an acronym for therapeutic response criteria, based on PET imaging.

 

RECIST is an acronym for therapeutic response criteria based on CT,

 

which looks at changes in size of tumor sites.

 

By using PERCIST criteria, which is based on the metabolic signature,

 

which is the FDG uptaking tumor and the changes after treatment.

 

Treatment response, monitoring is better than using the older RECIST criteria.

 

Responders versus non-responders on early response PET/CT is

 

associated with better survival in some studies with a threshold

 

of SUV reduction between 30 to 80% being advocated.

 

PET cannot exclude minimal residual disease as there is

 

cases of significant recurrence even after a SUV decline.

 

So going back to the multi-choice question from earlier, which of the following

 

statements regarding FDG PET/CT imaging of esophageal cancer is true?

 

The answer is, C, the PET/CT has superior specificity

 

than CT/endoscopic Ultrasound for staging of regional nodal metastases.

 

Therefore, the combination of PET/CT with CT and

 

endoscopic ultrasound together will have the highest diagnostic accuracy.

 

Some take home points.

 

Esophageal cancer is a biologically aggressive,

 

metabolically active malignancy.

 

FDG PET/CT is a useful imaging modality for staging and restaging

 

of esophageal cancer, prognostication, and assessing treatment response.

 

FDG PET/CT has good specificity for loco-regional nodal metastases.

 

FDG PET/CT is a whole-body technique with good accuracy for

 

distant metastatic disease.

 

This is a bibliography of relevent articles on PET/CT for esophagus cancer.

 

So PET/CT is a relatively new, very powerful imaging methodology for

 

the diagnosis and staging of a wide range of cancers, including esophageal cancer.

 

I'd like to thank you for your participation in this educational lecture,

 

hope that its been helpful.

 

Thank you.