According to estimates from the National Cancer Institute, there were 37,680 new cases of pancreatic cancer in 2008 with 34,290 deaths. These numbers represent, with chilling clarity, how deadly this form of cancer is. The 16th edition of Harrison’s Principles of Internal Medicine states that pancreatic cancer results in the death of greater than 98% of individuals with the tumor. The causes of pancreatic cancer are not well known. Cigarette smoking is the single largest risk factor for developing pancreatic cancer, though the mechanism by which this occurs is not certain. Chronic pancreatitis is another cause. Chronic pancreatitis refers to inflammation of the pancreas as a result of many things, including alcoholism, drug use, infection, and others. Long-standing diabetes is also a risk factor for cancer.
The term “pancreatic cancer” encompasses several types of tumors that can arise from the pancreas. To understand the differences in these tumors, it is necessary to understand how the pancreas is organized and what it does.
The pancreas is located behind the stomach and just below the lungs. In general, it is thought of as having two different functions. These are referred to as endocrine and exocrine functions. The endocrine functions are those that come to mind when we think of the pancreas and so we will deal with those first.
Endocrine is a term that refers to the function of certain organs whereby they secrete a chemical into the blood that as effects throughout the body. The pancreas secretes three main chemicals into the blood: insulin, glucagon, and somatostatin. Insulin is necessary for reducing the level of sugar in the blood and helping to get the sugar into cells for use and storage in response to a meal. Glucagon has the opposite effect. When you have not eaten for a while, glucagon is secreted by the pancreas and acts on the liver to release stores of sugar. This sugar is then used by other organs, such as the brain and muscles that need it. Somatostatin has other, less easily defined functions that relate to regulating the levels of insulin, glucagon, and other hormones. Each of the three hormones is made in a different type of cell within the pancreas. Insulin is made in Beta cells, glucagon in Alpha cells, and somatostatin in Delta cells. Each of these cells can give rise to cancer.
The other function of the pancreas is referred to as its exocrine function. Exocrine refers to the secretion of chemicals onto the surface of the body or the inside of the intestine. In the case of the pancreas, it secretes chemicals into the intestine that aide in digestion. The cells that make these chemicals are different from the cells that make insulin, glucagon, and somatostatin. These cells are referred to as acinar cells.
So, we now know that the pancreas is made up of two parts, the exocrine and endocrine parts. Each of these parts is further broken down into specific types of cells that make certain chemicals. Any of the cells in the pancreas can give rise to cancer. The severity and aggressiveness of the cancer are determined by the type of cell from which the cancer arises.
Almost all (95%) of pancreatic cancers are referred to as adenocarcinomas. These are very aggressive, very deadly tumors. Average life expectancy after diagnosis of adenocarcinoma of the pancreas is 6 months. These tumors arise from the exocrine pancreas often originate in the ducts that allow the chemicals to reach the intestine. The other 5% of pancreatic cancers arise from the endocrine pancreas where insulin and glucagon are made. These tumors are generally less aggressive and are often caught at an earlier stage than adenocarcinoma. A biopsy is usually necessary to make the diagnosis.
The symptoms of pancreatic cancer include abdominal pain, weight loss, jaundice (yellowing of the skin and eyes), a feeling of being full sooner than normal when eating, loss of appetite, and changes in the stool. These symptoms are by no means specific and can be due to a variety of other conditions. Other testing is necessary to delineate the exact cause of these symptoms.
Tests may include a CT scan of the abdomen, abdominal ultrasound, regular x-rays with contrast, blood tests, stool tests, and possible exploratory surgery. CT examination is by far the most specific test (next to surgery) and has an 80% chance of picking up a cancer if one exists. Other tests that might be done include and ERCP, PET scan, MRI, endoscopic ultrasound. ERCP is a test in which a tube is inserted into the mouth and into the small intestine so that dye can be injected into the pancreatic duct. The dye is then visualized by x-ray to determine if it flows freely though the pancreatic duct or not. A lack of free flow suggests obstruction. If obstruction is noted, a piece of tissue will be taken if possible, but open surgery is the next likely step to make a final diagnosis.
Treatment is aimed at completely removing the tumor or, if that is not possible, using chemotherapy to suppress the growth of the tumor. Unfortunately, if complete surgical resection (i.e. removal) is not an option, then there is little potential for curing the tumor. The median survival for patients in whom the tumor cannot be removed is 6 months. Management at that point is directed at comfort. Narcotics and chemotherapy may both be used to reduce the discomfort associated with the tumor. Surgical procedures may also be undertaken to allow for drainage of pancreatic contents to reduce discomfort. All of these options are palliative.
Mayer RJ. Chapter 79: Pancreatic Cancer. In: Kasper, Braunwald, Fauci, Hauser, Longo, Jameson. Harrison’s Principles of Internal Medicine, 16th ed. 2005. New York: McGraw-Hill. P. 537-8.