Pancreatic Cancer

Fast Facts:

• 3% of all cancers
• 6% of all cancer deaths
• Aggressive: 5-year survival rate of 5%

Types:

• Adenocarcinomas: 95%
• Neuroendocrine Tumors: 4-5%
• Lymphoma: <1%

Indications for PET/CT Scan: 

Diagnosis: 

• Valuable role in ruling out malignancy for an equivocal mass noted on a prior CT or MRI (estimated accuracy of 85%-93%).

Initial Staging: 

• Limited value in the assessment of local resectability. A contrast-enhanced CT scan is required to determine the relationship of the mass to the adjacent vasculature. 
• The utility of PET/CT for staging lies in its assessment of regional nodes and distant metastatic disease.

Distant Disease: Most commonly to the liver, peritoneum, lung, pleura, bones and adrenal glands.

Assessing Response to Therapy & Prognosis: 

• Early Response: Non-responders can be offered alternative therapy.
• Late Response: Assess success or failure of therapy, and ultimate outcome.

Recurrence & Restaging: 

• Restaging suspected recurrence.
• Distinguishing recurrence from post-therapeutic inflammation.

Criteria for “Active Malignancy”: 

Although many patients with pancreatic cancer have a biopsy-proven diagnosis prior to PET/CT scanning, it is not uncommon for a PET/CT scan to be ordered to assess whether an equivocal lesion is benign or malignant.

• Any focus of metabolic activity (well-defined or not) involving the pancreas should raise a suspicion for malignancy. 
• An accompanying well-defined soft tissue abnormality will not always be detected on the co-registered CT images (especially as these studies are almost always performed without intravenous contrast).
• The more focal and the more intense the uptake, the more likely the lesion is to be malignant.
• The presence of associated hypermetabolic nodes dramatically increases the likelihood of malignancy.

What We Report:  

Size, metabolic activity & location of the primary lesion and representative metastatic lesions are reported. 

• Primary Lesion: Size, metabolic activity & location.
• Loco-Regional Disease: Usually hypermetabolic lymph nodes.
• Distant Disease: Most commonly to the liver, peritoneum, lung, pleura, bones and adrenal glands.

False Positives:

• Inflammation: Pancreatitis (acute or chronic) can cause intense parenchymal uptake.  Such uptake, however, is usually non-focal, involving a significant segment of the pancreas.   
• Benign Lesions: Several benign lesions can demonstrate varying degrees of FDG uptake, including intraductal papillary mucinous neoplasm (IPMN), serous cystadenoma, and hemorrhagic pseudocysts.

False Negatives:

• Lesions < 8.0 mm, considered “beneath the resolution of PET.”
• Hyperglycemia: While elevated blood glucose can limit the PET/CT evaluation of any malignancy (addressed in detail, here), many radiologists believe it to have an especially significant effect in decreasing the FDG uptake of some pancreatic lesions.