Most patients with pancreatic cancer are diagnosed at a late stage, because in its early stage the disease is completely asymptomatic, causing no symptoms at all. This delay is the reason that the tumour is unresectable, meaning it cannot be completely removed by surgery, or metastatic, meaning it has spread to distant sites, by the time it is found.
How the disease presents depends on where in the pancreas it sits. Tumours of the body and tail are more silent than tumours of the head, and they are larger by the time they cause symptoms. The reason is anatomical: a tumour in the head lies next to the common bile duct and the pancreatic duct, which are major ducts, so it can block them and involve the biliary tract and the rest of the pancreas early. A tumour in the tail is far from the common bile duct and does not obstruct it at all. As a result, patients with body and tail tumours tend to present with more advanced disease.
A tumour in the head of the pancreas can produce two groups of obstructive symptoms:
- Biliary obstruction, from blockage of the bile duct — jaundice (yellowing of the skin and eyes), dark-coloured urine and pruritus (itching).
- Pancreatic duct obstruction, which stops digestive enzymes reaching the gut — exocrine pancreatic insufficiency, with steatorrhoea (fatty stools) and malabsorption.
Pain is the major complaint of patients with pancreatic cancer. It is caused by invasion of the tumour into the coeliac and superior mesenteric nerve plexuses, the networks of nerves in the upper abdomen. The pain is characteristically low in intensity, vague and poorly localised, felt mostly in the upper abdomen, and it can radiate to the back. It is sometimes post-prandial, meaning it comes after meals, and the pain can lead to weight loss.
Other, non-specific findings include nausea, fatigue, weight loss and anorexia. Abnormal glucose metabolism is also common: about 85% of patients have an abnormal fasting glucose at diagnosis, and roughly half already have diabetes, which is often of recent onset. Pancreatic cancer itself disturbs glucose metabolism, which is why new-onset diabetes can be an early clue to it.
Obstruction of the pancreatic duct can, rarely, present as acute pancreatitis with a raised serum amylase. Pancreatic cancer should therefore be suspected in a patient who develops acute pancreatitis without any recognised cause.