Men who have difficulty conceiving children are 2.6 times as likely to have highly aggressive prostate cancer and 60% more likely to have slow-growing tumors, researchers reported Monday. Although the absolute risk of developing prostate cancer was still low in these men, the findings suggest that such men should be screened for prostate cancer at an earlier age, said Dr. Otis Brawley, chief medical officer of the American Cancer Society.
Previous studies have looked at the relationship between prostate cancer and the number of children a man has, but they have produced differing results. Some suggested that fatherhood was protective, while others suggested that it increased risk. Because the number of children a man has may not be an accurate reflector of his fertility, Dr. Thomas J. Walsh of the University of Washington School of Medicine and his colleagues decided to study men who had been evaluated for infertility.
The team studied 22,562 men who had been evaluated from 1967 to 1998 at 15 California infertility centers, comparing them with a similar group of healthy men from the general population. They reported in the journal Cancer that they identified 168 cases of prostate cancer among the men, about the same as the 185 cases that would be expected in a group that size. That suggests that simply being evaluated for infertility does not affect the incidence of prostate cancer.
Overall, 0.4% of the fertile men developed prostate cancer during the decade of follow-up, compared with 1.2% of those diagnosed as infertile. Taking age into account, that translated to a 160% increased risk of developing aggressive tumors and a 60% increased risk of developing slow-growing tumors, the team reported.
It is not clear why infertile men have a higher risk. Walsh speculated that the risk might result from exposure to environmental toxins in the womb that cause damage to the male chromosome, but argued that more research needs to be done, both to confirm their findings and to explore potential mechanisms.
Prostate cancer is the most common cancer in men after skin cancer, striking 192,000 American men each year and killing 27,000. Other risk factors include older age, a family history of the disease, obesity and being African American. Most national organizations now recommend that men be offered screening beginning at age 50, but there is a widespread controversy about this. Some critics argue that the screening leads to an unacceptably high rate of invasive procedures in men who do not have cancer, leading to impotence, urinary incontinence and other problems.
-- Thomas H. Maugh II