Getting to the bottom of colonoscopy guidelines

Dr. Keith Roach

Could you please advise what the current recommendation is as far as follow-up colonoscopies are concerned? It has always been my understanding from what I have read that virtually all colon cancers start as polyps in the colon and that it takes between fifive and 10 years for a polyp to become cancerous. My doctor says that a colonoscopy every 10 years is suffificient. Do you agree? I’m wondering why so many people I know are having a colonoscopy way more often. — Anon.

Answer: Although there are rare instances where colon cancer begins without polyps, you are right that the vast majority of colon cancers start as polyps. So development can be prevented by removing polyps that might become cancer.

The optimum interval between colonoscopies depends on what was found on the fifirst colonoscopy. If everything was completely normal, or if there were only tiny hyperplastic polyps (these are less likely to become cancerous), then a 10-year interval is recommended. With a small tubular adenoma (at higher risk for developing cancer), a fifififififiveyear interval is commonly recommended. Those with larger or higher-risk polyps, such as villous adenomas, a three-year interval is recommended. For people with genetic syndromes (such as Lynch), annual colonoscopies are recommended after age 40.

Q: My son-in-law tested positive for the BRCA gene. His maternal grandmother died young from breast cancer, and his aunt is now terminally ill with pancreatic and liver cancers after having breast cancer. In addition, his mother has had breast cancer, which metastasized to her leg bone. He has already been told that he should be tested yearly for cancer. He is 33 years old. What are the ramififications for this young man? Furthermore, how does this affffect any future children he and my daughter might have? — P.M.

A: There are two BRCA genes, BRCA1 and BRCA2. Either increases risk for cancer in those who carry the gene; however, the degree of risk depends on which BRCA gene is involved, the specifific mutation involved and the history of cancers in the family. The gene is present in both men and women: The BRCA1 gene is on Chromosome 17, BRCA2 is on Chromosome 13. These genes are tumor suppressor genes, and losing their function reduces the body’s ability to repair DNA.

Men with BRCA mutations are at increased risk for colon, pancreatic, prostate and male breast cancers. Recommendations for screening for these cancers must be highly individualized. I am surprised that your son-in-law hasn’t already met with a genetic counselor: It should have been done before he was tested, and certainly afterward, to review his risks in detail.

There is a 50 percent risk for each child that the gene will be passed on.