Men who had radiation for rectal cancer at lower risk for prostate cancer

Men who have had radiation for rectal cancer have a reduced risk for later prostate cancer.  After treatment they had 72 percent less prostate cancer than other men of similar ages and race.

Researchers at Massachusetts General Hospital in Boston studied three groups of men, comparing their rates of prostate cancer to what would be expected in a similar male population:

• 1,574 men with local or regional rectal cancer who were treated with both radiation and sphincter-sparing surgery.
• 3,114 men with rectal cancer who had surgery but no radiation
• 24.578 men with local or regional colon cancer who did not receive radiation.

Among the 1,574 men who had both surgery and radiation, there were 20 who eventually developed prostate cancer — far fewer than would have been expected.  The ratio of actually observed cases of prostate cancer to that which would have been expected (O/E) was 0.28 or a 72 percent reduced occurrence.

However, there was little difference between the actual number of subsequent prostate cancers and those which would have been expected in either the men who had rectal cancer but no radiation or men who had colon cancer.  O/E for rectal cancer was .94 and for colon cancer 1.09.

Average age of the group of men with rectal cancer who were treated with radiation was 64 and their median survival time after treatment was 76 months or more than 6 years.

The research team was led by Karen E. Hoffman, MD, MHSc at Harvard Medical School and the Department of Radiation Oncology at Massachusetts General Hospital.

SOURCE: Hoffman et al, Cancer, Volume 112, Number 4, February 2008.