NEW YORK (Reuters Health) – Data from the Geneva Cancer Registry show an increased long-term risk of colon cancer after external radiation therapy for prostate cancer, according to a report in the September 1st issue of the International Journal of Cancer.

Dr. Christine Bouchardy from the University of Geneva, Switzerland and colleagues analyzed data on 1,134 men diagnosed with prostate cancer between 1980 and 1998 who survived for at least 5 years after diagnosis. Of these, 264 were treated with external radiotherapy.

During follow-up, 19 men developed colorectal cancer.

Among irradiated patients, the standardized incidence ratio (SIR) for colorectal cancer was 3.4. On further analysis, the risk was significantly increased for colon cancer but not for rectal cancer.

The risk of colon cancer was also elevated in the 5- to 9-year period after diagnosis.

The study team concludes that, ?the risk of second cancer after irradiation, although probably small, needs nevertheless to be carefully monitored.”

Reference:
Int J Cancer 2008;123:1141-1145.