Pancreatic Cancer: Causes, Symptoms and Treatments
Cancer is a class of diseases characterized by out-of-control cell growth, and pancreatic cancer occurs when this uncontrolled cell growth begins in the pancreas.
Rather than developing into healthy, normal pancreas tissue, these abnormal cells continue dividing and form lumps or masses of tissue called tumors. Tumors then interfere with the main functions of the pancreas. If a tumor stays in one spot and demonstrates limited growth, it is generally considered to be benign.
More dangerous, or malignant, tumors form when the cancer cells migrate to other parts of the body through the blood or lymphatic systems. When a tumor successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a more serious condition that is very difficult to treat.
In the United States each year, over 30,000 people are diagnosed with pancreatic cancer. Europe sees more than 60,000 diagnoses each year. Because pancreatic cancer is usually diagnosed late into its development, the five-year survival rate after diagnosis is less than 5%.
What Is The Pancreas?
Location of the pancreas - diagram
The pancreas is a 6-inch long organ located behind the stomach in the back of the abdomen. It is spongy and shaped somewhat like a fish, extended horizontally across the abdomen. The head of the pancreas is on the right side of the abdomen where the stomach is attached to the first part of the small intestine (the duodenum). The tail of the pancreas - its narrowest part - extends to the left side of the abdomen next to the spleen.
The pancreas contains exocrine and endocrine glands that create pancreatic juices, hormones, and insulin. Pancreatic juices, or enzymes, made by the exocrine glands are released into the intestines by way of a series of ducts in order to help digest fat, proteins, and carbohydrates. Over 95% of the pancreas is made up of exocrine glands and ducts. The endocrine cells are arranged in small clusters called islets of Langerhans, which release insulin and glucagon into the bloodstream. These two hormones manage levels of sugar in the blood. When they are not working properly, the result is often diabetes.
More information on the pancreas itself is available in our article What Is The Pancreas? What Does The Pancreas Do?
How Is Pancreatic Cancer Classified?
Pancreatic cancer is categorized depending on whether it affects the exocrine or endocrine functions of the pancreas. There is an important distinction between the two broad types of pancreatic cancer because they have different risk factors, causes, symptoms, diagnostic tests, treatments, and prognoses.
CT scan of pancreas
A CT scan of the pancreas.
Tumors that affect the exocrine functions are the most common type of pancreatic cancer. Sometimes these tumors or cysts are benign, called cystadenomas. However, it is more likely to find malignant tumors called adenocarcinomas, which account for 95% of exocrine pancreatic cancers. Adenocarcinomas typically start in gland cells in the ducts of the pancreas, but they can also arise from pancreatic enzyme cells (acinar cell carcinoma).
Other types of pancreatic cancers that are associated with exocrine functions include adenosquamous carcinomas, squamous cell carcinomas, and giant cell carcinomas, named for their appearances underneath a microscope. There is also a disease called ampullary cancer (carcinoma of the ampulla of Vater) that starts where the bile duct and pancreatic duct meet the duodenum of the small intestine.
Tumors that affect the endocrine functions of the pancreas are called neuroendocrine or islet cell tumors, but these are fairly uncommon. These tumors are named for the type of hormone-producing cell that is initially affected. For example: insulinomas (insulin), glucagonomas (glucagon), gastrinomas (gastrin), somatostatinomas (somatostatin), and VIPomas (vasoactive intestinal peptide or VIP). Functioning islet cell tumors still make hormones, while non-functioning ones do not. Most of these tumors are benign, but non-functioning tumors are more likely to be malignant, islet cell carcinomas.
What Causes Pancreatic Cancer?
Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer results. Pancreatic cancer cells do not experience programmatic death, but instead continue to grow and divide. Although scientists do not know exactly what causes these cells to behave this way, they have identified several potential risk factors.
Genes - The DNA Type
Cells can experience uncontrolled growth if there is damage or mutations in the DNA, and therefore, damage to the genes involved in cell division. Four key types of genes are responsible for the cell division process: oncogenes tell cells when to divide, tumor suppressor genes tell cells when not to divide, suicide genes control apoptosis and tell cells to kill themselves if something goes wrong, and DNA-repair genes instruct cells to repair damaged DNA.
Cancer occurs when a cell's gene mutations make the cell unable to correct DNA damage and unable to commit suicide. Similarly, cancer is a result of mutations that inhibit oncogene and tumor suppressor gene functions, leading to uncontrollable cell growth. If you have DNA mutations of oncogenes or tumor suppressor genes that lead to pancreatic cancer, it is likely that the mutation was a result of factors that affected DNA after you were born rather than a result of inheritance from parents.
Genes - The Family Type
Cancer can be the result of a genetic predisposition that is inherited from family members. It is possible to be born with certain genetic mutations or a fault in a gene that makes one statistically more likely to develop cancer later in life. About 10% of pancreatic cancers are though to be caused by inherited gene mutations. Genetic syndromes that are associated with pancreatic cancer include hereditary breast and ovarian cancer syndrome, melanoma, pancreatitis, and non-polyposis colorectal cancer (Lynch syndrome).
Carcinogens
Carcinogens are a class of substances that are directly responsible for damaging DNA, promoting or aiding cancer. Certain pesticides, dyes, and chemicals used in metal refining are thought to be carcinogenic, increasing the risk of developing pancreatic cancer. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. Theses free radicals damage cells, affecting their ability to function normally, and the result can be cancerous growths.
Other Medical Factors
As we age, there is an increase in the number of possible cancer-causing mutations in our DNA. This makes age an important risk factor for pancreatic cancer, especially for those over the age of 60. There are several other diseases that have been associated with an increased risk of cancer of the pancreas.
These include cirrhosis or scarring of the liver, helicobacter pylori infection (infection of the stomach with the ulcer-causing bacteria H. pylori), diabetes mellitus, chronic pancreatitis (inflammation of the pancreas), and gingivitis or periodontal disease.
Traits, Habits, And Diet
Pancreatic cancers are more likely to exist in men than in women, and among African-Americans than among whites. Smoking cigarettes increases one's risk of pancreatic cancer by a factor of 2 or 3. Even smokeless tobacco has been noted as a risk factor.
Diet and obesity have also been linked to cancers of the pancreas. People who do not exercise much and who are obese are more likely to develop pancreatic cancer. In addition, those who eat diets low in vegetables and fruits and high in red meat and fat are more likely to be diagnosed with the disease. Alcohol consumption is also considered a risk factor for pancreatic cancer. Long term, heavy drinking leads to chronic pancreatitis, which is a known risk factor for pancreatic cancer.
What Are The Symptoms Of Pancreatic Cancer?
Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumor is. Pancreatic cancer is often called a "silent" disease because it rarely shows early symptoms and presents non-specific later symptoms. Tumors of the pancreas cancers are usually too small to cause symptoms. However, when the cancer grows, symptoms include:
man holding his stomach
Pain in the upper abdomen from the tumor pushing against nerves
A painless yellowing of the skin and eyes and darkening of the urine called jaundice, created when the cancer interferes with the bile duct and the liver.
Loss of appetite, nausea, and vomiting
Significant weight loss and weakness
Acholic stool (pale or grey stool) and steatorrhea (excess fat in stool)
These symptoms of pancreatic cancer have numerous other causes, making it difficult to diagnose the disease before it is in an advanced stage.
Cancers of the pancreas are also associated with Trousseau's sign - spontaneous blood clots formed in the portal blood vessels, deep veins of the arms and legs, or other superficial veins. Clinical depression is another symptom that is sometimes reported before the cancer is diagnosed.
If the cancer spreads, or metastasizes, additional symptoms can present themselves in the newly affected area. Symptoms of metastasis ultimately depend on the location to which the cancer has spread.
Islet cell or neuroendocrine cancers of the pancreas may cause the organ to produce too much insulin or hormones. This may lead to weak or dizzy feelings, chills, muscle spasms, or diarrhea.
On the next page we look at how pancreatic cancer is diagnosed and the available treatments for pancreatic cancer.
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