Background: randomized trial to evaluate the addition of 4-month androgen deprivation to high dose radiotherapy in localized intermediate risk prostate adenocarcinoma patients. Methods: eligible patients were randomly assigned to high dose radiotherapy (prostate 80 Gy; seminal vesicles 46 Gy) either alone (group RT) or in combination with 4-month androgen deprivation (flutamide + triptoreline starting 2 months before radiotherapy, group AD-RT). Lymphadenectomy was mandatory when the risk of node involvement was > 10% (Partin). The primary endpoint was biochemical (Phoenix definition) or clinical control. Secondary endpoints included survival, toxicity (CTCAE v3) and quality of life. The a-priori sample size was 450 patients (0.90 power to detect an increase from 75 to 85%, bilateral α = 0.05). An intermediate analysis was planned 6 months after the last patient inclusion (bilateral α = 0.005). Results: 377 patients were entered between October 2003 and July 2010. The trial was prematurely closed, due to slow accrual. Intention-to-treat analysis included 366 patients (188 RT, 178 AD-RT). Prognostic factors were well balanced between groups. The median follow-up duration was 37 months (range: 0 to 63). At 3 years, biochemical or clinical control probabilities were 86% [95% CI: 80%–92%] and 92% [87%–97%] in RT and AD-RT groups respectively (p = 0.09). Biochemical control probabilities were 91% [86%–96%] and 97% [94%–99.6%] in RT and AD-RT groups respectively (p = 0.04). The cumulative hazards of grade 3-4 toxicities were 6.4% and 2.8% (p=0.41) for digestive tract, 2.6% and 6.1% (p=0.14) for urinary tract, in RT and AD-RT groups respectively. Conclusions: The observed difference in favour of AD-RT did not reach statistical significance as defined for the present intermediary analysis. The final analysis is scheduled in 2013.