Adding radiotherapy to androgen deprivation therapy (ADT) improves outcomes in patients with locally advanced prostate cancer (PCa) and can be considered a standard treatment option, researchers concluded.

Nicolas Mottet, MD, of Clinique Mutualiste in St. Etienne, France, and colleagues randomized 264 PCa patients with T3-4 or pT3N0M0 disease to receive ADT alone or ADT plus radiotherapy. The primary outcome was the five-year progression-free survival (PFS) using the American Society for Therapeutic Radiology and Oncology (ASTRO) and Phoenix definitions of biochemical recurrence.

After a median follow-up of 67 months, the five-year progression-free survival (PFS) was 60.9% for the combined therapy group versus 8.5% for those received ADT alone, according to the ASTRO definition, and 64.7% versus 15.4% using the Phoenix definition, investigators reported online ahead of print in European Urology. The differences between the groups were statistically significant.

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Clinical progression occurred in 43 patients (33.1%) in the ADT-only group and 13 (9.8%) in the combined therapy group.

The researchers stated that their data suggest that the PFS benefit is due to locoregional control. The combined therapy group had significantly lower rates of locoregional progression compared with the ADT-only arm (9.8% vs. 29.2%), as well as lower rates of metastatic progression (3% vs. 10.8%).

Overall and disease-specific survival did not differ significantly between treatment arms. Overall survival for the combined therapy and ADT-only arm was 71.4% and 71.5%, respectively, and disease-specific survival was 93.2% and 86.2%, respectively.

With respect to safety, 10 men in the combined therapy group (8%) and three (2%) in the ADT-only group reported serious adverse events related to treatment, according to the researchers. Four of these patients—all in the combined therapy group—died, but no death was directly related to treatment, the investigators stated.

Study limitations included a relatively small study population and a relatively short follow-up period, the authors noted. In addition, they acknowledged that the use of radiotherapy to treat 24 patients who progressed after ADT alone may have had an impact on the survival outcome.