COLORECTAL CANCER: PREVENTION AND EARLY DETECTION
T. Carter Towne, M.D. & Myron Lewis, M.D. Approximately 160,000 new cases of colorectal cancer will be diagnosed this year, with 60,000 deaths related to this diagnosis.
Colon cancer is the third most common cancer in the United Stated after lung and breast cancer. The risk of developing colon cancer begins to increase slightly at age 40, sharply rises at age 50, and doubles with each decade thereafter.
Along with advancing age, other factors that increase risk include a previous colon cancer or polyp, certain family cancer syndromes, the diagnosis of colon cancer or polyp in a close relative (parent, sibling, or child), and history of inflammatory bowel disease (ulcerative colitis or Crohn’s disease of some extended duration).
The most common symptoms include rectal bleeding, change in bowel habits (normal to diarrhea or normal to constipation), and change in the caliber or consistency of the stool. Other less common signs or symptoms would include abdominal pain or unexplained weight loss.
This diagnosis is usually made by testing the stool for blood, and then looking at the colon either by using X-rays (barium enema) or with a scope (sigmoidoscopy or colonoscopy). Treatment consists of surgery to remove the tumor if possible, sometimes combined with radiation (rectal cancer only) and/or chemotherapy.
An individual’s self-imposed habits and dietary customs are potential risk factors for cancer. A diet high in fat content, low in fiber, and rich in red meats represents an established risk for colorectal cancer. In terms of prevention, a well-balanced diet, low in fat content, with intake restricted to less than 30% of total calories is most important. The diet should include adequate intake of fruits and vegetables, (five servings each) every day, along with a cereal bran fiber providing at least 25-30 grams daily, which is the amount that has been shown to reduce risk of developing colon cancer. Two other factors that may contribute to the development of colon cancer are physical inactivity and cigarette smoking. The latter is associated with increased risk of polyp growth, and regular exercise may increase colonic activity and lessen exposure to certain cancer producing agents (carcinogens).
Risk Factors for Colon Cancer
- Improper diet
- Physical inactivity
- Cigarette smoking
- Several agents can be classified as chemopreventive, as they may retard or prevent progression of colorectal cancer in high-risk individuals. Included in this group would be aspirin, certain arthritis medications called non-steroidal anti-inflammatory drugs, vitamins such as folic acid, high doses of calcium, and estrogen replacement therapy.
There is a well-established relationship between improved survival and early-stage detection with respect to many forms of cancer, and this is particularly true in colorectal cancer.
A sequence of events is felt to occur in the colon that results in transformation of normal colonic tissue into polyps and ultimately a cancer. There are genetic and environmental factors involved, but the process takes many years to occur (approximately 10-15), and therefore colorectal cancer is very suitable for screening large segments of the population (those at higher risk for early detection).
Routine screening as recommended by the American Cancer Society, World Health Organization, and American College of Physicians, includes a digital rectal examination by your physician after age 40 and each year thereafter. Beginning by at least age 50, everyone should have a stool specimen checked annually for blood. All people age 50 and older (and earlier if at risk) should have a sigmoidoscopy - an examination of the lower colon with a flexible, lighted tube – every three to five years. Based on these examinations, other studies may become necessary, such as a barium enema or colonoscopy. To date, there is statistical evidence to support screening for early detection by these methods, with demonstrated reduction in death rates and ultimate health care costs related to colorectal cancer.