Pancreatic cancer

Definition

Pancreatic cancer is a disease in which cancerous cells are found within the tissues of the pancreas. The pancreas is a six-inch long, pear-shaped gland that lies behind the stomach, surrounded by other digestive organs, such as the liver, gallbladder, and small intestine. It has two main functions, to produce digestive juices that help break down food, and to produce hormones (like insulin) that control how the body stores and uses the food.

Description

The part of the pancreas that produces the digestive juices is called the exocrine pancreas, and almost 95% of pancreatic cancers occur in the tissues of the exocrine pancreas. The hormone-producing area of the pancreas is the endocrine pancreas and only 5% of the tumors originate there.

Though pancreatic cancer accounts for only 2-3% of all cancers, it is the fourth most frequent cause of cancer deaths. It is estimated that at least 29,000 new cases of pancreatic cancer will be diagnosed in the United States in 1998. Unfortunately, cancer of the pancreas is often fatal, and only 18% will survive one year after diagnosis. The five-year survival rate is 4%. This is because by the time a patient exhibits symptoms, and the cancer is diagnosed, it is no longer in its early stages. It has usually spread to other organs such as the lung and the liver.

The incidence of pancreatic cancer increases with age, and most cases are detected in individuals aged 60 or older. Men are also 30% more likely to develop cancer of the pancreas than are women. African Americans have been noted to have a higher frequency of pancreatic cancer than European Americans and Asian Americans. However, whether the increase is because of race or the influence of diet cannot be really ascertained. Studies have shown that among Africans and Asians whose diet is lower in fat than African Americans and Asian Americans, the incidence of pancreatic cancer is significantly lower.

Causes & symptoms

Although the exact cause for pancreatic cancer remains unknown, several risk factors, such as smoking and diets rich in red meat and fat, have been shown to increase the susceptibility to this particular cancer. It has been observed that a third of pancreatic cancer cases occur among smokers. Therefore, smoking is regarded as the single greatest risk factor for this cancer.

Although the association between diabetes and pancreatic cancer is not known, the disease is more common among diabetics. Conditions such as chronic pancreatitis (long-term inflammation of the pancreas) have also been associated with an increased risk for pancreatic cancer. Some research data shows that exposure to certain substances, such as gasoline and dry cleaning chemicals increases the risk of this cancer.

The most common signs and symptoms of the disease are:

• Abdominal pain is generally a sign that the pancreatic cancer has spread to the surrounding area and the tumor is pressing down on the nerves. Typically, the pain is in the back and relieved by sitting up and bending forward.
• Weight loss that is not due to drastic dieting or exercising is a common occurrence in pancreatic cancer patients. Weight loss could be due to loss of appetite and improper digestion.
• Digestive problems, diarrhea, and nausea may often occur in patients because the pancreas plays an important role in making certain digestive juices that break down the fatty foods.
• Gallbladder enlargement may sometimes occur, because the pancreatic tumor expands in size and presses down on the ducts leading from the gallbladder to the small intestine. Hence, the bile accumulates in the gallbladder causing it to become enlarged (a positive Courvoisier sign).
• Jaundice (a yellowish discoloration of the whites of the eyes and the skin) due to an accumulation of a substance called "bilirubin" in these tissues. Jaundice is secondary, and related, to associated obstruction of the common bile duct by the cancer. Many other conditions, such as hepatitis and the presence of gallstones also cause jaundice.

Diagnosis

The first step in diagnosing pancreatic cancer is a thorough medical history and a complete physical examination. The doctor will inquire about the severity of the pain, how long it has been present, its location, etc. A physical examination will be conducted to check for fluid accumulation, or any lumps, or masses, in the abdomen. The skin and the whites of the eyes will be checked for jaundice. Blood tests will be performed to rule out the possibility of liver diseases that can also contribute to jaundice.

Imaging tests such as CT scans, MRI imaging, or ultrasonography may be ordered in order to get a detailed picture of the internal organs. This will also help to check whether the cancer has spread to other organs beyond the pancreas.

The doctor may perform a test known as ERCP (endoscopic retrograde cholangiopancreatography), where a long thin tube is passed down the patient's throat and food pipe (through an endoscope and under endoscopic guidance) into the stomach. This enables the doctor to check for any blockage of the pancreatic ducts that may be due to cancer. The doctor can also place a small brush in the tube and collect some cells from the pancreas. These can then be examined microscopically, and any cancerous cells, if existing, can be detected.

The most definitive test for pancreatic cancer is a biopsy, where a sample of the tumor is removed and examined microscopically.

Treatment

Pancreatic cancer can be treated by any of the three standard modalities: surgery, radiation therapy, or chemotherapy.

If the imaging studies show that the cancer is contained within the pancreas, the doctors will attempt surgery to remove all the cancer. Depending on the location of the tumor, different types of surgery can be performed, where either the whole pancreas or only parts of the pancreas are removed. If, however, the imaging studies show that the cancer has spread beyond the pancreas and cannot be completely removed, the doctors will perform surgery to relieve symptoms, or to prevent complications.

If the tumor is too widespread to be removed by surgery, radiation therapy in combination with chemotherapy is used.

Prognosis

The disease is often fatal. Once diagnosed with this cancer, 95% of patients will die within five years. More than 80% of the patients will not survive the first year after initial diagnosis. The poor prognosis is because of late diagnosis; the pancreas is a small gland located deep within the abdominal cavity, and, hence, cannot be seen or felt during routine physical examination. There are no early symptoms, and by the time the symptoms are manifested, the cancer has already spread to other organs and is in an advanced stage. Doctors and researchers are working hard to find new methods of diagnosing pancreatic cancer before it spreads.

Prevention

Since the exact cause of pancreatic cancer is not known, there are no guidelines for prevention. The wisest approach would be to avoid all the risk factors for pancreatic cancer.

Quitting cigarette smoking will certainly reduce the risk for many cancers, including pancreatic cancer. In countries where the diet is low in fat, the incidence of pancreatic cancer is much lower. The American Cancer Society recommends a diet rich in fruits, vegetables, and dietary fiber in order to reduce the risk of pancreatic cancer.

Key Terms

Biopsy

The surgical removal and microscopic examination of living tissue for diagnostic purposes.

Cancer

A fatal disease, if left untreated, of neoplasms (tumors or growths). Cancer cells spread in the body and invade other tissue.

Chemotherapy

A treatment of the cancer with synthetic drugs that destroy the tumor either by inhibiting the growth of the cancerous cells or by killing the cancer cells.

Computerized tomography (CT) scan

A medical procedure where a series of x-rays are taken and put together by a computer in order to form detailed pictures of areas inside the body.

Courvoisier sign

Related to Courvoisier's Law which states: When the common bile duct is obstructed by a stone, dilation of the gallbladder is rare; when the duct is obstructed some other way, dilation is common.

Diabetes

A condition where dietary carbohydrates, especially sugars, are not efficiently metabolized by the body, leading to the presence of sugar (or glucose) in the blood and urine. One of the triggering factors for diabetes is malfunction of the pancreas, resulting in insufficient production of the hormone insulin.

Gallbladder

A small sac-like gland that lies below the liver and stores the bile produced in the liver. Ducts (tubes) leading out of the gallbladder deposit the bile in the small intestine.

Gallstones

Protein depositions that cause an obstruction in the gallbladder, or in the ducts leading out of the gallbladder.

Hepatitis

A liver disease characterized by inflammation of the liver cells (hepatocytes).

Jaundice

A condition where there is a yellowish discoloration of the skin and the whites of the eyes due to accumulation of a substance known as bilirubin in these tissues and the blood.

Magnetic resonance imaging (MRI)

A medical procedure used for diagnostic purposes where pictures of areas inside the body can be created using a magnet linked to a computer.

Radiation therapy

A treatment using high energy radiation from x-ray machines, cobalt, radium, or other sources.

Ultrasonogram

A procedure where high-frequency sound waves that cannot be heard by human ears are bounced off internal organs and tissues. These sound waves produce a pattern of echoes which are then used by the computer to create sonograms or pictures of areas inside the body.

Further Reading

For Your Information

Books

• Dollinger, Malin. Everyone's Guide to Cancer Therapy. Kansas City, MO: Somerville House Books Limited, 1994.
• Merck Manual of Diagnosis and Therapy, edited by Robert Berkow, et al. 16th ed. Rahway, NJ: Merck Research Laboratories, 1992.
• Morra, Marion E. Choices. New York: Avon Books, 1994.

  Organizations

• American Cancer Society. 1599 Clifton Road N.E., Atlanta, Georgia 30329. (800) 227-2345.
• Cancer Research Institute. 681 Fifth Avenue, New York, N.Y. 10022. (800) 992-2623.
• National Cancer Institute. 9000 Rockville Pike, Bethesda, MD 20892. (800) 422-6237.

  Other

• Cancer Information Database. American Cancer Society.
• NCI/PDQ Patient Statement, Pancreatic Cancer. National Cancer Institute.
• What You Need To Know About Cancer of The Pancreas. April 1996. NIH publication number 96-150. National Cancer Institute.

Gale Encyclopedia of Medicine. Gale Research, 1999.