ASTRO 2015: The Addition of 24 Months of Daily Antiandrogen Therapy Improves Overall Survival Following Recurrence After a Radical Prostatectomy
Prostate cancer patients who face recurrence after radical prostatectomy have better overall survival rates with a combination of salvage radiation therapy and 24 months of antiandrogen therapy than with radiation therapy alone, according to research (Abstract LBA5) presented by Shipley et al on October 19, 2015, at the American Society for Radiation Oncology (ASTRO) 57th Annual Meeting in San Antonio, Texas.
Many men with prostate cancer who undergo radical prostatectomy experience recurrence, as evidenced by an elevated prostate specific antigen (PSA) level. These patients are then often given salvage radiation therapy to the prostate tumor bed.
Study Details
RTOG 9601 was a large phase III, double-blinded, placebo-controlled trial that evaluated whether long-term antiandrogen therapy combined with salvage radiation therapy would improve overall survival and other cancer control outcomes for prostate cancer patients who had failed radical prostatectomy. Conducted from 1998 to 2003, the study included 761 prostate cancer patients from centers across the United States and Canada and compared a salvage regimen of only radiation therapy to one of radiation therapy plus antiandrogen therapy.
The study group included patients who had undergone a radical prostatectomy and had developed elevated PSA levels from 0.2 to 4.0 ng/mL with prostate tumors classified as either T2, pN0 and a positive surgical margin or T3, pN0.
The patients were randomly assigned to receive either radiation therapy of 64.6 Gy in 36 fractions of 1.8 Gy plus 24 months of antiandrogen therapy therapy of 150 mg of daily bicalutamide during and after radiation therapy, or to receive the radiation therapy regimen plus a placebo. A total of 384 patients were assigned to the radiation therapy plus antiandrogen therapy group, and 377 patients were assigned to the radiation therapy plus placebo group.
Follow-up Findings
With a median follow-up of 12.6 years, the study results showed that the actuarial overall survival at 10 years was 82% for the radiation therapy plus antiandrogen therapy patients and 78% for the radiation therapy plus placebo patients (hazard ratio [HR] = 0.75, 95% confidence interval [CI] = 0.58–0.98, two-sided P = .036).
Data indicated that the addition of antiandrogen therapy decreased the rate of death by prostate cancer and decreased the risk of the cancer metastasizing. The 12-year incidence of prostate cancer centrally reviewed deaths was 2.3% for the radiation therapy plus antiandrogen therapy group, compared to 7.5% for the radiation therapy plus placebo group (P < .001). At 12 years, the cancer had metastasized in 51 patients (14%) in the radiation therapy plus antiandrogen therapy group, compared to 83 patients (23%) in the radiation therapy plus placebo group (P < .001).
Additionally, late grade 3 and grade 4 bladder and bowel side effects were similar in both groups, whereas 70% of men in the radiation therapy plus antiandrogen therapy group reported swelling of the breasts, compared to 11% from the radiation therapy plus placebo group.
“Over the last 25 years, many men with intermediate-risk prostate cancer have undergone radical prostatectomy, yet many will face recurrence in 1 to 4 years with a rising PSA,” said William U. Shipley, MD, FACR, FASTRO, Andres Soriano Distinguished Professor of Radiation Oncology at Massachusetts General Hospital and Harvard Medical School. “Our results show that salvage radiation therapy plus androgen blockage, when compared to radiation therapy with a placebo, improved long-term overall survival and reduced death from prostate cancer without adding significantly to radiation toxicity.”
He continued, “Because prostate cancer progresses slowly, follow-up of over 12 years was necessary to demonstrate a statistically better patient survival with combined antiandrogen therapy and radiation therapy. Further statistical analyses, which are underway, may identify subgroups of prostate cancer patients who may not benefit from hormone therapy added to salvage radiation therapy and others for whom it may be especially beneficial.”
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
