What is colon cancer and how is it related to colon polyps?
Colon cancer is a malignant growth starting on the colon lining which invade into the wall of the colon. It can then spread to lymph nodes or into the blood stream and then become disseminated (metastatic) to the liver, lung, bones or brain. Polyps are benign growths on the colon lining. There is a polyp-cancer sequence for polyps called adenomas. In time there are progressive alterations to the chromosomes of the polyp’s cells occur. After a certain degree of genetic changes, these cells can become malignant and the polyp will turn into a cancer. In this common situation, these genetic changes are found in the cells of the lesion itself but not in other cells of the body such as the blood, which can be easily tested. There a number of conditions, however, where a genetic abnormality can be found in all of the body’s cells and this includes familial adenomatous polyposis (FAP), hereditary non-polyposis colon cancer (HNPCC) and familial colon cancer syndrome in Ashkenazi Jews.
How common and serious are polyps and cancer?
Benign polyps occur in 30% of people by age 50. The lifetime risk for colon cancer is 5%. The risk starts at age 40 with marked increase at 50 and the peak at 75. There are 130,000 new cases per year – overall this is the third most common type of cancer. There are 60,000 deaths per year and is the second leading cause of cancer deaths.
What increases the risk for a person to get colon cancer?
Simply getting into middle age represents a significant risk factor for colon cancer. The highest risk groups for colon cancer include ulcerative colitis, previous history of polyps or cancer, family history of colon cancer, certain genetic conditions (familial adenomatous polyposis, hereditary non-polyposis colon cancer and familial colon cancer syndrome in Ashkenazi Jews) and a personal history of female cancer. Smoking, drinking and physical inactivity are additional risk factors for colon cancer.
The family history is more significant with young first-degree relatives and when multiple family members have had colon cancer. If the relative was over 55 years old, the risk is double; if the relative was 45-54, the risk triples; and if the relative was less than 45, the risk quadruples.
How can colon cancer be prevented?
It has been established that removal of the adenoma polyps can prevent cancer from developing. There are several ways to screen for polyps and cancer. The American Cancer Society recommendations for standard risk individuals 50 years and older are the following: either 1) Stool testing for occult (chemical traces) blood yearly plus flexible sigmoidoscopy every 5 years or 2) Colonoscopy every 10 years. When there is a high risk setting, colonoscopy is the preferred test. When there is a strong family history of cancer, genetic counseling and diagnostic testing may also be indicated. Starting on 7/1/01, Medicare approves of and will pay for colonoscopy every 10 years for standard risk individuals.
Can changes in diet and vitamin intake help prevent colon cancer?
The following measures are generally thought to be protective: fat reduction, increased Fiber intake, increased intake of anti-carcinogens found in vegetables, fruits, legumes, nuts and grains especially wheat bran (insoluble fiber) and increased intake of calcium, vitamin E and selenium.
How are polyps and colon cancer treated?
Polyps are removed during colonoscopy using electrocautery with snares or biopsy forceps passed through the instrument. Cancer generally requires surgery. Radiation and chemotherapy are used when clinically indicated.