The addition of six months of androgen suppression therapy (AST) to radiation therapy improves survival of patients with clinically localized prostate cancer, according to a study in the current issue of the Journal of the American Medical Association.
“Combining three years of AST with 70 Gy RT (dose of radiation therapy) has been shown to improve survival rates for patients with locally advanced prostate cancer,” the authors provide as background information. “However, the toxicity of long-term AST can be significant, particularly in elderly patients.” AST is a treatment that inhibits the release of androgen, the male sex hormone.
Anthony V. D’Amico, M.D., Ph.D., from Brigham and Women’s Hospital, Boston, and colleagues, assessed the survival benefit of 3-dimensional conformal radiation therapy (3D-CRT) alone or in combination with 6 months of AST in patients with clinically localized prostate cancer. The 206 patients were randomized to receive 70 Gy 3D-CRT alone (n=104) or in combination with 6 months of AST (n = 102) from December 1, 1995 to April 15, 2001. The patients included those with a prostate specific antigen (PSA) of at least 10 ng/mL, a Gleason score (grading system for prostate cancer) of at least 7, or radiographic evidence of disease outside the prostate. Follow-up visits were performed at the end of radiation treatment every 3 months for 2 years, every 6 months for an additional 3 years, and then annually until death or January 15, 2004, the end of the study.
“After a median (midpoint) follow-up of 4.52 years, patients randomized to receive 3D-CRT plus AST had significantly higher survival, lower prostate cancer-specific mortality [death], and higher survival free of salvage AST [salvage treatment is used when cancer recurs after initial treatment],” the authors found. Standardized estimates of 5-year survival rates were 88 percent in the 3D-CRT plus AST group vs. 78 percent in the 3D-CRT group. Rates of survival free of salvage AST at 5 years were 82 percent in the 3D-CRT plus AST group vs. 57 percent in the 3D-CRT group.” The researchers note there were 6 deaths due to prostate cancer and 17 from other causes for patients receiving 3D-CRT. For patients receiving 3D-CRT plus AST, no deaths occurred due to prostate cancer and 12 were from other causes.
“Given that many men treated for prostate cancer are often older and that AST use of more than one year has been shown to cause osteopenia, impairment of memory, attention and executive functions, and prolongation of the QT interval [heart rhythm], in addition to anemia, muscle loss in exchange for body fat, hot flashes, and impotence, minimizing these effects by decreasing AST duration could profoundly impact a patient’s quality of life. Therefore, the clinically significant implication of our study is that a 6-month course of AST in patients receiving RT who have clinically localized prostate cancer may be sufficient to reduce the risk of death,” the authors conclude.