SAN DIEGO—Men with locally advanced prostate cancer (PCa) have a better chance of survival when they add radiation therapy (RT) to their hormone therapy, according to research presented at the 52nd annual meeting of the American Society for Radiation Oncology.

The interim results—which came from the largest randomized study of its kind—were recommended for release by an independent Data and Safety Monitoring Committee in light of their importance.

The study included 1,205 men with locally advanced PCa in the United Kingdom, Canada, and the United States. Researchers randomized 602 patients to receive either lifelong androgen-deprivation therapy (ADT) alone (bilateral orchiectomy or luteinizing hormone-releasing hormone agonist therapy) and 603 patients to receive external beam RT plus lifelong ADT. The primary endpoint was overall survival. Secondary endpoints included disease-specific survival, time to disease progression, and quality of life.

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After a median follow-up of six years, 320 patients died: 175 in the ADT alone group and 145 in RT plus ADT group, which translated into a 23% reduction in the risk of death from any cause in the combination treatment group. Of the 320 patients, 140 died from PCa: 89 in the ADT alone arm and 51 in the RT plus ADT group, which translated into a 43% decreased risk of disease-specific death in the combination treatment arm. Toxicity rates were similar for both cohorts, with the rates of grade 3-4 toxicity less than 2%.

Noting that the interim results “indicate substantial benefits in overall survival and disease-specific survival for the combined modality approach,” the study authors concluded that ADT plus RT should be the standard treatment approach for patients with locally advanced PCa.

Although the number of men treated with combined hormone and radiation therapy has increased in recent years, treatment variation continues to exist, and many men are still treated solely with hormone therapy, according to lead study author Malcolm Mason, MD, a radiation oncologist at Cardiff University in Cardiff, Wales, U.K. Most likely, this is due to preconceived ideas about radiation toxicity.

“The reality is, as judged by the evidence, that radiation therapy as given in our study simply isn’t that toxic. The treatment we offer our patients must surely be dictated by the best available evidence, and not by our own preconceived ideas. The best evidence is that for otherwise fit men with locally advanced disease, hormone therapy plus radiotherapy should be the standard of care.” 

The study was jointly conducted by the National Cancer Institute of Canada, the United Kingdom Medical Research Council, and the Southwest Oncology Group in the United States. The final analysis will be conducted in 2012.