An international study led by Toronto researchers has found that almost 50 per cent of men over age 60 have prostate cancer at the time of death, but die of other causes.

The study, published in the Journal of the National Cancer Institute, involved posthumous examinations of 320 men in from Russia and Japan between 2008 and 2011. None of the men had been diagnosed with prostate cancer before their deaths.

Lead author Dr. Alexandre Zlotta, director of uro-oncology at Mount Sinai Hospital’s Murray Koffler Urologic Wellness Centre and a scientist with Mount Sinai’s Lunenfeld-Tanenbaum Research Institute, said the study underscores the need for better screening methods that don’t just determine if a man has prostate cancer but whether it is an aggressive and life-threatening form of the disease.

The current widespread use of prostate-specific antigen (PSA) testing in North America increases the likelihood of over-detection of low-risk prostate cancers. Men with low-risk prostate cancers can end up undergoing unnecessary treatment such as radiation and surgery, which in turn can lead to problems with incontinence and sexual function.

The study involved autopsies of Caucasian men from Russia who share environmental characteristics with North American men, such as reduced sun exposure and a high-fat diet, both of which have been implicated in increased risk for prostate cancer.

Researchers included autopsied men from Japan in the study because diagnosed incidence of prostate cancer is much lower there than it is in North America. Japanese men typically have a lower death rate from prostate cancer as well as a very different diet from North American men.

PSA screening in both countries is not widespread.

By studying these two distinct populations, researchers showed that despite differences in incidence and mortality rates, and in genetic and lifestyle factors, the prevalence of prostate cancer was similar in both Caucasian and Asian men. In fact, the disease was even more aggressive in Asians.

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