The ratio of free to total prostate specific antigen (PSA) in a man's blood may predict at the time of diagnosis whether prostate cancer will be an aggressive, fast-growing disease or a non-aggressive, slow-growing type of cancer. This discovery by researchers at the National Institute on Aging (NIA) and colleagues at the Johns Hopkins University School of Medicine is published in the March, 1997, journal, Urology.
"The ability to differentiate between an aggressive and non-aggressive form of prostate cancer when the disease is diagnosed early puts the physician and patient in a better position to make decisions about treatment," says Dr. E. Jeffrey Metter, Medical Officer for the Baltimore Longitudinal Study of Aging (BLSA) of the NIA, one of the study's authors. "Physicians need a reliable way of distinguishing which cancers are serious, life-threatening tumors and which ones are not. The ratio of free to total PSA in sera may give physicians this information."
Today, physicians have effective means of diagnosing prostate cancer, but there is great debate about which treatment is best for a cancer diagnosed in the early stage-watchful waiting, surgery to remove a localized cancer, or radiation therapy. Each has advantages and disadvantages. Radiation and surgery may be associated, in some cases, with complications including impotence and incontinence. Watchful waiting means living with cancer and possibly missing an opportunity for cure.
"This preliminary study suggests that the free to total PSA ratio may be valuable to the physician at the time of cancer diagnosis to help in the choice of management since the more aggressive cancers need to be treated," says Metter.
PSA, an enzyme produced by the prostate gland, is found in high concentration in semen where it acts to liquefy the seminal fluid after ejaculation so that sperm can swim freely. Some PSA leaks into the blood stream from prostatic cells, more so in the presence of pros
Contact: Suzanne Lewis
NIH/National Institute on Aging