STANFORD, Calif. - "Serendipity" rather than science plays a prominent role in the current diagnosis of prostate cancer, according to Stanford University Medical Center researchers. A new study finds that prostate specific antigen (PSA), a marker traditionally used by doctors as an indicator of prostate cancer risk, is clinically unreliable.
"For any level of serum PSA - from 2 to 9 nanograms per milliliter - there is no way you can turn to a patient and say you've got prostate cancer," said Thomas Stamey, MD, professor of urology and primary author of the study published in the January issue of The Journal of Urology.
The results showed that low levels of PSA are not meaningfully related to prostate cancer, but are rather caused by harmless increases in prostate size, commonly known as benign prostatic hyperplasia or BPH. Prostate cancer is being over-diagnosed and over-treated because of the misconception that PSA is primarily a reflection of prostate cancer, Stamey said.
Levels of PSA, a normal product of the prostate gland, have been thought to increase in men with early prostate cancer. Men aged 50 or older whose PSA levels exceed a certain cutoff are monitored and may undergo prostate biopsy as standard procedure. But biopsies cannot distinguish between cancers that should be of concern and "small cancers that will never bother a patient if they live to the age of Methuselah," Stamey said.
Prostate cancer is the most common cancer in men. The American Cancer Society estimates that 189,000 cases of prostate cancer will be diagnosed in the United States this year alone, and one in six men will be diagnosed with the disease at some point in their lives. "Prostate cancer is incredibly ubiquitous," Stamey said. "It starts in men in their 30s and by age 90, almost all men will have some cancer in their prostate." However, the risk of dying from prostate cancer is very low, Stamey added.
Contact: Ruthann Richter
Stanford University Medical Center