Pancreatic Metastases

Pancreatic metastases are secondary tumours in the pancreas from a non-pancreatic primary cancer. They account for 2% to 5% of malignant pancreatic masses and are found in some autopsy series in a higher share of patients with widespread cancer.

Renal cell carcinoma is the commonest source (about 60% to 70% of resected cases), followed by lung, colorectal, breast and gastric cancer, sarcoma and melanoma. Renal cell metastases can appear 10 to 20 years after nephrectomy, and in about 20% to 50% the pancreas is the only site of disease.

Pathophysiology.

Spread is by blood or lymph, or by direct invasion from adjacent organs. Renal cell metastases are hypervascular, and they tend to be solitary and slow growing, so selected patients do well after resection.

Many patients have no symptoms and the lesion is found at surveillance imaging. Others have abdominal or back pain, weight loss, obstructive jaundice, pancreatitis, gastrointestinal bleeding or new diabetes.

Red flags.

• Jaundice or cholangitis.
• Upper gastrointestinal bleeding from tumour erosion.
• Recurrent pancreatitis from duct obstruction.
• Rapid weight loss.

Review the cancer history and previous imaging. Multiphase CT or magnetic resonance imaging shows a well defined mass; renal cell metastases enhance avidly in the arterial phase, unlike ductal adenocarcinoma. CA 19-9 is usually normal. Endoscopic ultrasound with fine needle biopsy and immunostaining (for example PAX8, CD10 and carbonic anhydrase IX for renal cell carcinoma) confirms the diagnosis. Stage with chest, abdomen and pelvis CT, and consider positron emission tomography.

Differential diagnosis.

• Pancreatic ductal adenocarcinoma.
• Pancreatic neuroendocrine tumour.
• Pancreatic lymphoma.
• Autoimmune pancreatitis.
• Intrapancreatic accessory spleen.

Resect isolated or oligometastatic renal cell metastases when the patient is fit and other disease is absent or controlled; five year survival after resection is 60% to 80%. Other primaries are resected only when the disease is isolated and biologically slow. Otherwise systemic treatment for the primary cancer is given.

• Sunitinib (metastatic renal cell carcinoma): 50 mg orally once daily for 4 weeks, then 2 weeks off, repeated until progression or unacceptable toxicity; maximum 50 mg daily; monitor blood pressure, thyroid function, full blood count, liver tests and cardiac function; reduce in steps of 12.5 mg to a minimum of 25 mg for toxicity, use 37.5 mg with strong CYP3A4 inhibitors, and use caution in severe hepatic impairment.
• Pembrolizumab or other immune checkpoint combinations are used for renal cell carcinoma and melanoma by oncology decision.

Relieve biliary obstruction with an endoscopic metal stent when resection is not planned.

Monitoring. Imaging every 3 to 6 months for 2 years after resection, then yearly for at least 10 years in renal cell carcinoma.

Referral and escalation. Pancreatic surgery and oncology multidisciplinary review.