Rectal cancer is cancer of the rectum: the last six inches of the digestive system that sits between the colon (large intestine) and the anus. It shares many similarities with colon cancer and the two cancers are commonly referred to as colorectal cancer. Most colorectal cancers begin as a polyp – a growth of tissue on the lining of the colon or rectum. Not all polyps are dangerous, but the type known as an adenoma may become cancerous unless removed. Colorectal cancers usually develop slowly over many years and are treatable if diagnosed early through regular screening.
The relationship among diet, exercise, weight and colorectal cancer is well known. A diet high in red meats, processed meats and charred meats is known to increase the risk of colorectal cancer. Conversely, a diet low in such meats and high in fruits and vegetables lowers the risk. The benefits of high-fiber diets and vitamins/supplements have so far proven inconclusive.
Obesity, smoking and alcohol consumption (more than two drinks per day for men and one per day for women) are linked to increased risk of colorectal cancer. Other risk factors include: age (over 90 percent of cases occur after the age of 50), previous polyps or colorectal cancer; a history of bowel disease, such as Crohn's or ulcerative colitis; a family history and genetic factors; and Type 2 diabetes.
Rectal cancer often does not produce any symptoms until later in the disease, and many symptoms are also caused by non-cancerous factors. Symptoms include changes in bowel habits for more than a few days; feeling the need for a bowel movement even after having had one; rectal bleeding; cramping or abdominal pain; weakness and fatigue; and unexpected weight loss.
The best ways to prevent colorectal cancers are to control weight, diet and alcohol consumption and to exercise frequently. For those with a family history of these cancers, genetic testing is available.
Screening is very important. The death rates from rectal and colon cancers has been declining for two decades because of the prevalence of screening and early detection. The American Cancer Society recommends that people at average risk for colon cancer have a screening test (flexible sigmoidoscopy, colonoscopy or other type) beginning at age 50. The five-year survival rate for colon cancer now stands at about 90 percent when the cancer is found and treated early.
The primary treatment for both rectal and colon cancer is surgery. In rectal cancer, radiation and chemotherapy are often given before surgery to shrink the tumor before its removal. Depending on the stage and location of the tumor, different surgical methods may be used. For cancers in the lower area of the rectum, surgical instruments may be inserted through the anus. For those higher up, an abdominal incision may be required.
For advanced cases, the entire rectum might need to be removed (known as a proctectomy). This could result in the need for a temporary or permanent colostomy – an external waste bag for fecal matter.