Radiation therapy may increase risk of rectal cancer in men

The question: Using radiation to kill cancer cells has proved effective, but the therapy also has been connected, in some instances, to subsequent tumors. Might men who choose to treat prostate cancer with radiation be more likely to develop another type of cancer years later?

This study: analyzed data on 85,813 men who had been diagnosed with prostate cancer at least five years earlier and did not develop colorectal cancer within five years of the prostate cancer diagnosis. About 35 percent of the men had received radiation treatment; the others had had surgery to remove the cancer. After an average of nine years, 267 men had developed rectal cancer. Those who had undergone radiation were 70 percent more likely to develop this disease than were those who had surgery. Radiation did not seem to affect the rate of cancer in other parts of the body near the prostate.

Who may be affected by these findings? Men with prostate cancer, which will affect an estimated one in every six men in the United States.

Caveats: The authors indicated that overall rates of rectal cancer in both groups were low and suggested that prostate cancer treatments should not change based on these results. Estimates of time between radiation exposure and cancer are imprecise; cancer sometimes does not develop until 15 or more years after exposure.

Bottom line: Men with prostate cancer should discuss possible implications of radiation with a doctor before deciding on a treatment method. Men who have had radiation for prostate cancer should be checked regularly for signs of rectal cancer.

Find this study in the April issue of Gastroenterology; abstract available online at www.gastrojournal.org (click “Articles in Press”; then search for “prostate”).

Learn more about treating prostate cancer at http://familydoctor.org and www.cancer.gov/cancertopics.