Prostate gain from rectal cancer radiation

KISSIMMEE, Fla., Feb. 22 (UPI) -- Men undergoing radiation treatment for rectal cancer may get a bonus from the therapy: a substantial reduction in prostate cancer.

Doctors said Thursday that the external beam radiation used to kill rectal cancer cells may inadvertently strike the nearby prostate gland and have the unintended but beneficial side effect of reducing cancer risk in that walnut-sized organ.

"We found that the rate of prostate cancer in patients also being treated with external beam radiation for rectal cancer was about 70 percent less than we would expect," said Dr. Karen Hoffman, a clinical fellow in radiation oncology at Massachusetts General Hospital in Boston.

In a report at the 3rd Prostate Cancer Symposium in Kissimmee, Fla., Hoffman said she scrutinized data for the national Surveillance, Epidemiology, and End Results (SEER) registry and identified 1,574 men who were treated with radiation therapy from 1988 to 1997.

She compared the prostate-cancer rate to the rate in the general population and among 3,125 men treated for rectal cancer and 24,578 men who were treated for colon cancer but did not receive radiation therapy.

She found that the men not treated with radiation had about the same rate of prostate cancer as the general population.

"Rectal and prostate cancers tend to be diagnosed at a similar decade of life," Hoffman commented. "Inadvertent irradiation of the prostate during treatment for rectal cancer may sterilize or reduce sub-clinical prostate cancer or pre-cancerous lesions, or may impede prostate cancer development by altering the local hormonal or stromal milieu."