Androgen deprivation therapy and radiotherapy in intermediate-risk prostate cancer: A randomised phase III trial

Abstract

Background: The role of androgen deprivation therapy (ADT) in combination with radiotherapy (RT) in intermediate-risk prostate cancer (IRPC) remains controversial, particularly in patients receiving dose-escalated RT (DERT). We compared outcomes between patients with IRPC treated with ADT and two different doses of RT vs. RT alone.

Methods: From December 2000 to September 2010, 600 patients with IRPC were randomised to a three-arm trial consisting of 6 months of ADT plus RT 70 Gy (ADT + RT70) vs. ADT plus a DERT of 76 Gy (ADT + DERT76) vs. DERT of 76 Gy alone (DERT76). Primary end-point was biochemical failure (BF), and secondary end-points were overall survival (OS) and toxicity. RT toxicity was assessed by Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer criteria.

Findings: With a median follow-up of 11.3 years (interquartile range: 10.9-11.7), patients receiving DERT76 alone, compared with patients receiving ADT + RT70 and ADT + DERT76, had higher rates of BF (32%, 18% and 14%, respectively, p < 0.001), higher rates of prostate cancer progression (12%, 4.5% and 3.3%, respectively, p = 0.001) and more deaths due to prostate cancer (6.5%, 3.0% and 1.5%, respectively, p = 0.03) with no significant difference seen between ADT + RT70 and ADT + DERT76. There was no significant difference in OS between the 3 arms. A higher dose of RT (76 Gy) increased late gastrointestinal (GI) toxicity grade ≥ II compared with lower dose (70 Gy) (16% vs 5.3%, p < 0.001) with no statistical difference for late genitourinary toxicity.

Interpretation: In IRPC, the addition of 6 months of ADT to RT70 or DERT76 significantly improves BF and appears to decrease the risk of death from prostate cancer compared with DERT76 alone with no difference in OS. In the setting of IRPC, ADT plus RT 70 Gy yields effective disease control with a better GI toxicity profile. Clinicaltrials.gov#NCT00223145.

Keywords: Androgen deprivation therapy; Prostate cancer; Radiotherapy; Randomised trial.