NEW YORK (Reuters Health), Sep 4 - Data from the Geneva Cancer Registry show an increased long-term risk of colon cancer after external radiation therapy for prostate cancer.
"The risk of second cancer after irradiation, although probably small, needs nevertheless to be carefully monitored," the study team concludes in a report in the September 1 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 five years after diagnosis. Of these, 264 were treated with external radiotherapy.
During follow-up through the end of 2003, 19 men developed colorectal cancer.
Compared to the general population, there was no increased risk of colorectal cancer among non-irradiated patients. 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 (SIR = 4.0) but not for rectal cancer (SIR = 2.0).
The risk of colon cancer was elevated in the five- to nine-year period after diagnosis (SIR = 4.7), according to Bouchardy and colleagues.
"This serious long-term side effect should be discussed in view of the benefit of radiotherapy on local tumor control," they conclude.
Int J Cancer 2008;123:1141-1145.
Last Updated: 2008-09-03 8:30:19 -0400 (Reuters Health)
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