Adding 6 months of androgen deprivation therapy (ADT) to radiotherapy for localized prostate cancer (PCa) decreases the risk of biochemical progression, according to study data presented at the European Society for Radiotherapy and Oncology 33rd annual conference in Vienna.

The study, by Michel Bolla, MD, of Grenoble University Hospital in Grenoble, France, and colleagues, included 819 men with intermediate- or high-risk PCa recruited at 37 centers in 14 countries. Investigators randomly assigned patients to receive either radiotherapy alone or radiotherapy plus ADT, which consisted of two subcutaneous injections of luteinizing hormone-releasing hormone analogues. The first injection was given on the first day of radiotherapy, with the second injection given 3 months later.

Results showed that patients in the combination arm had a 47% decreased risk of biochemical progression compared with the radiotherapy only arm. Five years after treatment, 17.5% of patients in the combination arm experienced biochemical progression compared with 30.7% of patients who received radiotherapy alone. The researchers defined biochemical progression as a 2 ng/mL rise in PSA above nadir.

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Patients in the combination arm also had a reduced risk of clinical progression as indicated by biopsy or imaging. Five years after treatment, investigators observed no clinical progression in 88.7% of patients in the combination therapy compared with 80.8% of the monotherapy arm.