Pancreatic Cancer

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Pancreatic cancer is a disease characterized by abnormal growth of cells in the pancreas, a 15-cm- (6-inch-) long gland located behind the stomach. The pancreas is primarily made up of two different tissues with separate functions: the exocrine pancreas, which secretes enzymes into the digestive tract, aiding the breakdown of fats and proteins, and the endocrine pancreas, which secretes glucagon and insulin into the bloodstream to control blood sugar levels. Ninety-five percent of pancreatic cancers develop from the exocrine pancreas. The remaining 5 percent are often called neuroendocrine tumours or islet cell cancers; these develop from endocrine cells.

As is the case with many cancers, symptoms of pancreatic cancer are shared with those of many other illnesses. Symptoms often do not appear until the cancer has advanced to a late stage; they include abdominal pain, unexplained weight loss, problems with sugar metabolism, and difficulty digesting fatty foods. As a pancreatic tumour grows, it may block the common bile duct, which leads to a buildup of bilirubin in the blood and causes jaundice (a yellowing of the skin and eyes). Blockage of the bile duct may also cause the gallbladder to become enlarged.

The causes of pancreatic cancer vary and in many cases remain unknown. However, several factors have been identified that increase the risk of developing pancreatic cancer. Smoking is the most controllable risk factor, and up to 30 percent of pancreatic tumours have been linked to cigarette smoking. A diet high in animal products, particularly animal fat, also increases cancer risk. In addition, exposure to certain dyes, pesticides, and petroleum products may increase the probability of developing pancreatic cancer. Uncontrollable risk factors include age, sex — males are 30 percent more likely to develop cancers of the pancreas than are females — and illnesses such as diabetes mellitus and chronic pancreatitis. Some cases of pancreatic cancer are clearly the result of inherited defects, while other cases appear to stem from random or environmental causes.

Blood tests that assess various pancreatic and liver functions may suggest pancreatic cancer. If cancer is suspected, a needle biopsy is usually conducted to examine pancreatic cells for signs of cancer. Extensive use of imaging procedures is also required owing to the pancreas's location deep within the abdominal cavity. Imaging techniques include computed tomography (CT) scans, magnetic resonance imaging (MRI), and ultrasound. An endoscope can also be used for injection of dye into the bile duct, which allows better X-ray imaging of this structure. Angiography, a procedure that uses X rays to view blood vessels, is sometimes used to determine if the cancer has spread through the walls of the vessels feeding into the pancreas.

Once pancreatic cancer has been diagnosed, its stage is then determined to indicate how far the cancer has progressed. Stage I cancers are confined to the pancreas and have not spread to nearby lymph nodes. Stage II cancers have spread locally to the bile duct or small intestine but have not reached the lymph nodes, whereas stage III tumours have reached these nodes. Stage IV cancers have spread to other organs such as the lungs, liver, spleen, or colon.

The survival rate from pancreatic cancer is lower than that seen with many other cancers because the symptoms of pancreatic cancer often do not become obvious until the later stages of the disease. The average five-year survival rate from all stages of pancreatic cancer is extremely low, as is the one-year survival rate. However, survival rates are higher for patients who have their cancer diagnosed early in the course of the disease.

Surgery can be used to treat pancreatic cancer, but, given the poor prognosis of the disease and the unusually high number of complications associated with pancreatic surgery, surgery is usually reserved for cases in which there is a reasonable possibility of curing the disease. If the cancer is considered to be incurable, major surgery is done mainly to relieve symptoms or digestive problems. Islet cell tumours are often localized to the tail of the pancreas, and a distal pancreatectomy may be conducted to remove this portion of the pancreas along with the spleen.

Exocrine cancers are often treated with the Whipple procedure, a complicated surgical approach that removes all or part of the pancreas and nearby lymph nodes, the gallbladder, and portions of the stomach, small intestine, and bile duct. Serious complications often arise following this procedure, which requires an extensive hospital stay and considerable experience on the part of the surgeon. Other exocrine tumours are sometimes treated by complete removal of the pancreas (total pancreatectomy). Surgery can also be used to relieve complications of pancreatic cancers, such as obstruction of the bile duct. The bile duct may be redirected around the tumour, or a tube may be placed in the bile duct to keep it open.

Radiation therapy is sometimes used in conjunction with surgery — often prior to surgery to reduce a tumour to a more manageable size but also after surgery to destroy any remaining cancer cells. The position of the pancreas in the abdominal cavity makes it a difficult target for focused radiotherapy, but a procedure using radiotherapy simultaneously with surgery permits the surgeon to focus radiation directly onto the pancreas by moving obstructing organs aside. Side effects of this radiation therapy may include vomiting, diarrhea, fatigue, or skin irritations resembling a sunburn.

Chemotherapy is generally used when pancreatic cancers have spread to distant organs and may be required so that as many cancer cells as possible can be sought out and destroyed. Endocrine or islet cell tumours may be treated with hormone therapy, in which specific hormones are used to stop or slow the growth of the cancer in the endocrine cells.

Pancreatic cancer cannot be completely prevented, but risk can be decreased by reducing or eliminating cigarette smoking and following a diet low in animal products and high in fruits and vegetables.