Colorectal cancer is the third most common type of cancer in both men and women. It is also the second most common cause of cancer death in the United States. About 57,000 Americans die from this disease each year, and 145,000 new cases are diagnosed. Only lung cancer leads colorectal cancer in cancer deaths.
All Americans should take steps to reduce their risk of colorectal cancer and be screened for it regularly, but people with Type 2 diabetes have even more reason to educate themselves about this deadly disease. That’s because they are at greater risk of developing it than the rest of the population. This article offers some suggestions for lowering your risk as well as guidelines for screening for early detection.
What is colorectal cancer?
Colorectal cancer is a cancer, or tumor, that forms in the colon (the large intestine) and/or rectum (the last 8 to 10 inches of the colon). The colon is where water and nutrients are reabsorbed into the bloodstream as the last stage of digestion. At this point only waste remains. The waste is then eliminated through the rectum and anus.
Symptoms of colorectal cancer can include a change in bowel habits, blood in the stool, lower abdominal pain or cramping, fatigue, and vomiting. In the early stages, however, there are no symptoms. The early stages are also the time when it is easiest to cure. That’s why regular screening is so important. However, because so many Americans do not get screened according to the schedule recommended by the American Cancer Society, only about 39% of cases of colorectal cancer are found in the early stages.
Most cases of colorectal cancer develop from precancerous polyps, or adenomas. Polyps are growths in the colon that occur frequently in people over 50. Although most polyps are benign, or noncancerous, they can become malignant, or cancerous. While only 5% to 10% of all polyps become cancerous, all polyps should be surgically removed to test for cancer.
Some of the risk factors for colorectal cancer are modifiable, and some are not. Age is one that is not: 93% of people who develop colorectal cancer are over age 50. The average age at diagnosis is mid-60s.
Having a family history of colorectal cancer or a personal history of ulcerative colitis, Crohn’s disease, or a previous history of colorectal cancer is also a risk factor for colorectal cancer.
A rare, hereditary form of colorectal cancer is called hereditary nonpolyposis colon cancer, or HNPCC. Only 2% of all colorectal cancers fall into this category. The average age at diagnosis for this colorectal cancer is 44.
Another rare, inherited condition that raises the risk for colorectal cancer is familial adenomatous polyposis (FAP), in which hundreds of polyps form in the colon or rectum. When FAP is left untreated, colon cancer usually occurs by age 40. Only 1% of all colon cancers occur from FAP.
People with Type 2 diabetes have a 30% to 40% increased risk of colorectal cancer. While this connection is still being studied, there is evidence that hyperinsulinemia, or high levels of circulating insulin, increases the risk of colon cancer. It is thought that high insulin levels can damage the mucosa, or lining of the colon. Hyperinsulinemia is often associated with insulin resistance, in which the body’s cells are resistant to the action of insulin, so more insulin is needed to allow glucose into the cells. Insulin resistance is one of the major causes of high blood glucose levels in Type 2 diabetes.
Recent research studies have also suggested that people with Type 2 diabetes who have been on insulin therapy for more than one year have an increased incidence of colorectal cancer. However, more research needs to be done to clarify this issue. In the meantime, people who currently take insulin should not stop taking it. But they should follow the screening guidelines for early detection of colorectal cancer. It is estimated that with early detection and removal of polyps, risk for this disease can be decreased by 70%.