May 26, 1998
Despite technical refinements in the use of radioactive "seeds" to treat prostate cancer, a study by Johns Hopkins investigators casts doubt on its effectiveness in curing the disease. The radioactive pellets are put into the prostate in a procedure called interstitial radiotherapy.
"This is a wake-up call for physicians and their patients," says Patrick Walsh, M.D., professor of urology and director of the Brady Urological Institute and lead author of the study, published in the June issue of Urology. "Because studies from 20 years ago showed that interstitial radiotherapy often failed to completely eliminate local disease, we set out to determine whether recent refinements in seed placement improved the outcome and to develop a gold standard by which radiotherapy should be judged."
Using low levels of prostate specific antigen (PSA) as an end point, Walsh's group compared the outcomes in 76 men whose prostates were surgically removed at Hopkins with the published outcomes of 122 men who were treated with radioactive implants and no external radiation at the Northwest Institute in Seattle. PSA is a protein produced by the prostate. Increases in blood levels of PSA generally reflect either benign prostate enlargement or cancer.
The patients from Hopkins were carefully matched to the radiotherapy patients at Northwest Institute to ensure their PSA levels and Gleason scores before treatment were similar. The Gleason score is a measure on a scale of two to 10 of how aggressive prostate cancer appears under the microscope. The higher the score, the more aggressive the cancer is assumed to be.
The study showed that seven years after being treated, 98 percent of surgery patients had PSA levels that were undetectable (less than 0.2), while only 79 percent of men who underwent radiotherapy had PSA levels less than 0.5.
Walsh says results obtained with surgery should be used as the gold standard by which radiotherapy is judged. "That gold standard should be very low, or undetectable levels of PSA," he says. "The failure of interstitial seed therapy to achieve this goal questions whether it is eliminating the tumor adequately."
In an editorial accompanying Walsh's paper, Anthony D'Amico, M.D., Ph.D., of Harvard Medical School, said: "Although no definitive conclusions can be reached using nonrandomized retrospective data, this study provides the basis on which to design a prospective randomized clinical trail that could definitively compare PSA failure-free, cause-specific and overall survival...among these two treatment modalities...."
Walsh developed the anatomic approach to surgical removal of the prostate. This procedure, also called the nerve-sparing operation, preserves nerves that control sexual potency and bladder control.
Other authors of the paper include Thomas J. Polascik, Charles R. Pound and Theodore L. DeWeese.