WEDNESDAY, Nov. 10 (HealthDay News) -- Men taking hormone therapy for prostate cancer may have a slightly increased risk of developing colorectal cancer, a new study suggests.
Androgen deprivation therapy is often prescribed to treat prostate cancer. But its use in treating low-risk cancer is controversial, because two potential side effects, diabetes and obesity, are risk factors for colorectal cancer, the researchers say.
"We found that the use of androgen deprivation therapy, either through injections or through surgical castration, for prostate cancer was associated with a 30 to 40 percent increase in risk for colorectal cancer," said lead researcher Dr. Vahakn B. Shahinian, an assistant professor of internal medicine at the University of Michigan.
As experts debate whether routine prostate-specific antigen (PSA) testing causes many men to undergo unneeded treatment for prostate cancer, this finding appears to add another piece to the puzzle.
Shahinian noted that the absolute risk of developing colorectal cancer because of androgen deprivation therapy is very small. "Over a five-year period, I would say there would be no more than a 2.5 percent absolute risk of developing colorectal cancer," he said.
However, he thinks androgen deprivation therapy is overused.
Its value in treating late-stage prostate cancer that has metastasized is well-grounded, Shahinian said. And when combined with radiation, it is considered beneficial for treating locally advanced prostate cancer, he added.
But as primary therapy in lower-risk or localized tumors, "I don't think there is very good evidence for its use," Shahinian said.
"A lot of men are getting it in settings where they just have a biochemical recurrence of their tumor, so they just have an elevated PSA, but are otherwise doing fine -- that's a scenario where there isn't a proven benefit,"
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