Radiation therapy to the primary tumor in locally advanced prostate cancer is not “closing the barn door after the horse has bolted”

The National Cancer Institute of Canada (NCIC) Clinical Trials Group PR.3/Medical Research Council PR07/ Intergroup T94-0110 (1) was a randomized controlled trial (RCT) of radiation therapy (RT) and androgen deprivation therapy (ADT) vs. ADT alone, for men with locally advanced prostate cancer. The authors defined locally advanced as: (I) T3-4, N0/X, M0; or (II) T1-2 with prostate specific antigen (PSA) > 40 ng/mL; or (III) PSA 20-40 ng/mL and Gleason 8-10. Men were randomized to lifelong ADT vs. ADT + RT, 65-69 Gy in 1.8 Gy fractions, using 3D conformal RT, to the prostate and pelvis or prostate alone. Of the 1,205 patients treated between 1995 and 2005, 602 received ADT alone and 603 received ADT + RT. Overall survival (OS) was significantly improved in the patients allocated to ADT + RT [hazard ratio (HR) =0.70; 95% CI, 0.57-0.85; P<0.001]. Prostate cancer specific mortality (CSM) was improved in the patients allocated to ADT + RT (HR =0.46; 95% CI, 0.34-0.61; P<0.001). Although patients on ADT + RT arm reported a higher rate of gastrointestinal (GI) toxicity, only 2 of 589 patients had grade 3 or greater diarrhea at 24 months after RT.