Androgen Blockade Therapy for High-Risk Prostate Cancer Can Be Safely Reduced to 18 Months

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(ChemotherapyAdvisor) – Reducing androgen blockade therapy from 36 months to 18 months for men with high-risk prostate cancer does not harm patients' survival times, according to a prospective randomized phase 3 clinical trial reported at the 4th annual 2013 Genitourinary Cancers Symposium in Orlando, FL.

Long-term androgen blockade is a standard treatment for localized, high-risk prostate cancer; hormone therapy blocks men's ability to produce testosterone, which can hasten prostate tumor growth. But long-term treatment carries an increased risk of sexual and neurocognitive side effects that can degrade patients' quality of life.

“The results of our trial mean it is possible to reduce the duration of androgen blockade without putting our patients at risk,” reported coauthor Dr. Abdenour Nabid, MD, FRCP(C), of the University of Sherbrooke Center Hospital in Quebec City, Canada. “Shorter-term hormone therapy could have a big impact on the lives of men with prostate cancer, reducing the quantity and intensity of its unpleasant side effects as well as treatment costs.”

“We hope these results will convince doctors that they can stop hormone therapy after 1 and a half years instead of 2 to 3 years,” he added.

A total of 630 patients with high-risk, localized (node-negative) prostate cancer were randomly assigned to undergo either 18 months or 36 months of androgen blockade therapy with bicalutamide and goserelin, in addition to pelvic and prostate radiotherapy, Dr. Nabid reported. Patients with high-risk prostate cancer were identified as having a prostate-specific antigen (PSA) score greater than 20 ng/mL, a Gleason score higher than 7, or tumor stage T3-T4, he said.

At a median follow-up of 77 months, 77.1% of patients in the 36-month study arm and 76.2% of patients in the 18-month study arm were still alive, Dr. Nabid reported. Five-year and 10-year overall survival rates were also statistically similar (92.1% vs. 86.8% and 63.6% vs. 63.2%, respectively), he noted. Analysis of cancer-specific survival rates similarly showed that reducing androgen blockade duration did not increase the risk of dying of prostate cancer, with identical 10-year disease-specific survival rates of 87.2% in each study arm.

“This may well change the standard of care,” commented Bruce J. Roth, MD, of Washington University, St. Louis, MO, a panel moderator who was not associated with the study.

Reducing hormone therapy durations could reduce the severity of side effects like castration syndrome, which involves a loss in sexual interest, erectile dysfunction, fatigue, hot flashes, depression, anxiety, declines in neurocognitive function, and osteoporosis, noted Dr. Roth and Dr. Nabid. For patients who have “several more decades to live,” longer androgen blockade durations might not be justified because they possibly risk permanently lowering patients' testosterone levels and increasing cardiovascular events like heart attack, Dr. Roth cautioned.

The standard duration of up to 36 months for androgen blockade has emerged from clinical trial study designs over the years rather than evidence that it is the optimal treatment duration, Dr. Roth noted. “There's nothing magical about that duration,” he said.

The 2013 Genitourinary Cancers Symposium is co-sponsored by the American Gastroenterological Association (AGA) Institute, the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO) and the Society of Urologic Oncology (SUO).

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