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A Canadian researcher is hoping a new semen-based test for diagnosing prostate cancer could one day reduce the number of biopsies performed unnecessarily every year.

For years, doctors have relied on a test that measures the prostate-specific antigen levels in a man's blood to help diagnose prostate cancer. Men with elevated levels of PSA are often told to undergo a biopsy to determine whether their levels are high because of cancer or because of another benign cause, such as an enlarged prostate.

But biopsies are painful and carry some potentially serious risks, including infection, difficulty urinating and erectile dysfunction. And in some cases, biopsies may identify disease that is progressing so slowly it would never pose a major health threat. These are among the reasons that last year, the Canadian Task Force on Preventive Health Care recommended against routine screening using the PSA test.

Eleftherios Diamandis would like a better alternative that could reduce unnecessary biopsies. Dr. Diamandis, a researcher at Toronto's Mount Sinai Hospital, plans to spend the next two years developing a non-invasive test that can help determine when high PSA levels warrant concern. To do this, he will zero in on genetic mutations found in the semen of men with prostate cancer and use those biomarkers to screen other men for the disease.

Dr. Diamandis has collected semen samples from 100 men with confirmed prostate cancer and 100 men who do not have the disease. While it may seem unusual to study semen, Dr. Diamandis said it's likely it contains molecules from cancer, as some seminal fluid originates in the prostate. The researchers will look at the differences between the semen of both groups of men with the aim of identifying genetic mutations found only in those men with cancer.

If successful, Dr. Diamandis will do a larger validation trial to confirm those mutations are, in fact, linked to prostate cancer. The two-year project is being funded by the Canadian Cancer Society.

Whether this test can be applied in a real-world setting remains unknown, and years away, but Dr. Diamandis said he hopes to "save a lot of people from unnecessary biopsies."

Richard Hoffman, director of the division of internal medicine at the University of Iowa Carver College of Medicine, said the new semen-based test won't change diagnostic practices any time soon. Dr. Hoffman, who researches prostate screening, added that simply developing another test to identify cancer might not be a major help. Some cases of prostate cancer are aggressive while others grow slowly over many years, never posing a serious danger.

According to the Canadian Cancer Society, unnecessary treatment of non-life-threatening cancer can expose men to many side effects. The society says as many as half of the cancers identified by PSA tests may never need to be treated, but that most men do undergo treatment when they receive their cancer diagnosis.

Dr. Hoffman said there needs to be a better way of distinguishing life-threatening aggressive cancers from those that don't need treatment. It's possible that using genetic mutations could help researchers to do that.

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