Revision 69 for 'Pancreatic ductal adenocarcinoma'All Revisions
Pancreatic ductal adenocarcinoma
Pancreatic ductal adenocarcinoma makes up the vast majority (90%) of all pancreatic neoplasms, and remains a disease with very poor prognosis and high morbidity.
Pancreatic cancer accounts for 22% of all deaths due to gastrointestinal malignancy, and 5% of all cancer deaths 1. In general it is a malignancy of the elderly with over 80% of cases occurring after the age of 60 1.
Risk factors include:
- cigarette smoking: strongest environmental risk factor
- diet rich in animal fats and protein
- family history: three or more first-order relatives with pancreatic cancer results in ~20x risk 8
- hereditary syndromes 6
Perhaps surprisingly there is only a weak if at all present association with heavy alcohol consumption 1.
- pain (most common)
- Courvoisier’s gallbladder: painless jaundice and enlarged gallbladder
- Trousseau’s syndrome: migratory thrombophelebitis
- new onset diabetes mellitus
- lipase hypersecretion syndrome (10-15%) 9
- polyarthralgia and subcutaneous fat necrosis +/- lytic bone lesions
- elevated serum lipase and eosinophilia
Three precursor lesions for pancreatic adenocarcinoma have been identified 8:
- pancreatic intraepithelial neoplasia (PanIN)
- intraductal papillary mucinous neoplasm (IPMN)
- mucinous cystic neoplasm
Cancerous cells arise from pancreatic ductal epithelium. As the majority of tumours (90%) 1 are not resectable, this is mostly achieved with imaging (typically CT scan) although laparoscopy is often required to confirm resectability 1-2. The key to accurate staging is assessment of the SMA and coeliac axis, which if involved exclude the patient from any attempted resection 1-2.
- adenocarcinoma: majority
- acinar cell carcinoma of pancreas
- adenosquamous carcinoma of pancreas
- undifferentiated with osteoclasts giant cells
Location and classification
- head and uncinate process: two-thirds of cases
- body and tail: one-third of cases 1
Please see: pancreatic ductal adenocarcinoma staging.
Findings are non-specific and include:
- generally hypoechoic mass
- a double duct sign may be seen
CT is the work-horse of pancreatic imaging. Typically ductal adenocarcinomas appear as poorly defined masses with extensive surrounding desmoplastic reaction. They enhance poorly compared to adjacent normal pancreatic tissue and thus appear hypodense on arterial phase scans in 75-90% of cases, but may become isodense on delayed scans 1 (thus the need for multiple phase scanning when pancreatic cancer is the clinical question). Double duct sign may be seen.
CT correlates well with surgical findings in predicting unresectablitly (positive predictive value of 89-100% 3). The most important feature to assess locally is the relationship of the tumour to surrounding vessels (SMA and coeliac axis). If the tumour surrounds a vessel by more than 180 degrees then it is deemed T4 disease and is unresectable 3.
Signal characteristics include:
- T1: hypo intense c.f. normal pancreas 5
- T1 FS: hypo intense c.f. normal pancreas 5
- T1 + C (Gd): slower enhancement than normal pancreas, therefore dynamic injection with arterial phase imaging with fat saturation is ideal
- T2/FLAIR: variable (therefore not very useful) depending on the amount of reactive desmoplastic reaction 1,5
- MRCP: double duct sign may be seen
Barium meal/small bowel follow through
If large enough may demonstrate a reverse impression on the duodenum: Frostburg inverted 3 sign, or a wide duodenal sweep
Treatment and prognosis
Most tumours are not resectable at diagnosis.
Surgery for stage I and II (see staging of pancreatic cancer) does offer the chance of cure, with however high morbidity (20-30%) and mortality (5%) 3. Resection is performed with a Whipple operation.
Even when resection is possible, the majority of patients succumb to recurrence, with only a doubling of survival in operated patients 1 from 5 to 10% at 5 years 4. Almost a quarter of patients are dead 12 months following diagnosis 4.
General imaging differential considerations include: