Frequently Asked Questions About Colorectal Cancer


Who gets colorectal cancer?
The lifetime risk is about five to six percent for both men and women, with rates only slightly higher in men. Over 90 percent of new cases occur in individuals over the age of 50. Although there are families with high risk for colorectal cancers, at least 75 percent of patients have no family risk factors. African-Americans have a slightly increased risk (about 25 percent) compared to non-Hispanic whites and Hispanic/Latino Whites.

What is the incidence of colorectal cancer?
Colorectal cancer rates have been declining since 1998. These decreases are probably due to the increased use of colonoscopy, since precancerous polyps are frequently removed during this procedure. In addition, it is likely that advances in chemotherapy have resulted in improved survival and/or cure rates in patients with colorectal cancer.

What are the colorectal cancer risk factors?
A family history of colorectal cancer and a personal history of colon polyps or inflammatory bowel disease are the most important risk factors. Other risk factors reported to increase the risk are obesity, physical inactivity and a diet high in animal fat. Cigarette use and moderate alcohol consumption are also considered risk factors.

Can one decrease one's risk for developing colorectal cancer?
With few exceptions, the short answer is "probably not." Routine screening colonoscopy, beginning at age 50, will decrease or even eliminate the risk for developing colorectal cancer. Virtually all colon cancers begin as benign polyps. If these small benign tumors are removed at colonoscopy, cancer is prevented. In individuals with a positive family history of colorectal cancer, screening colonoscopy should be initiated earlier than age 50.

There are several dietary risk factors linked to increased and decreased risk for the development of colorectal cancer. Populations with high amounts of red meat have increased rates of colon cancer. Conversely, populations with diets high in grains, vegetables and fruits have decreased rates of colon cancer. Unfortunately, there are few data to suggest that one can change his or her risk of developing cancer by changing the diet. There are studies to suggest that several supplements can decrease the growth of benign polyps and, by assumption, the chance for developing colorectal cancer. Supplemental calcium, postmenopausal hormone replacement and aspirin or aspirin-like drugs all have been shown to slow polyp growth.

What is the difference between colorectal cancer, colon cancer and rectal cancer?
The colon and rectum combine to form the large intestine. The small bowel processes and absorbs nutrients, the large bowel absorbs water and minerals from the feces or stool and stores feces. The first four to five feet of the large bowel is within the abdominal cavity and is called the colon. The rectum is the final six to 12 inches of the large intestine as surrounded by the tissues of the pelvis: the spine in the back and the urinary system, prostate or vagina and uterus in the front. Although cancers of the colon and rectum are identical with regards to risk factors and biology, the treatments are distinctly different. Colon cancers are technically easier to remove and tumor recurrence in the abdomen near the site of the original cancer is unusual. Patients with colon cancer rarely require a permanent colostomy as part of their treatment.

Patients with rectal cancers, on the other hand, frequently do require a temporary or permanent colostomy. Furthermore, because the tumor can recur in the pelvis, many patients require radiation therapy as part of their treatment. Operations for rectal cancers are more difficult technically than operations for abdominal colon cancers (see "sphincter-preservation in patients with rectal cancer").