150 Background: Everolimus is able to stop the growth of tumor cells by blocking some of the enzymes needed for cell growth and by blocking blood flow to the tumor. Giving everolimus together with hormonotherapy and radiation therapy may kill more tumor cells. Methods: We conducted a phase I trial to evaluate the impact of everolimus (RAD001), an mTOR inhibitor, in patients treated concurrently with radiotherapy (RT) and ablative androgen treatment in high-risk locally advanced prostate cancer. Inclusion criteria were high-risk locally advanced non metastatic prostate cancer defined as clinical stage ≥ T3 or Gleason score ≥ 8 or PSA ≥ 20. The week before the beginning of RT, RAD001 was administered at different dose levels, twice daily, until the last day of irradiation. A nonsteroid antiandrogen was also given for 1 month at the beginning of RT. Prostate and seminal vesicle were irradiated up to 74Gy in 37 fractions of 2Gy with concomitant long-term LHRH analogue. The starting dose of RAD001 was 5mg/d with subsequent dose levels of 7.5 and 10 mg/d. The primary endpoint was the determination of the maximum tolerated dose (MTD). Dose escalation was implemented according to the continual reassessment method (CRM). Results: Fifteen patients were enrolled and 14 were assessable for toxicity and response. Significant toxicities were demonstrated at the 7.5 and 10 mg/d dose levels. Dose-limiting toxicity (DLT) occurred in two patients at dose level 7.5 mg/d and characterized by a grade 3 diarrhea and a grade 3 hydronephrosis due to dehydration and kidney lithiasis. DLT also occurred in two patients at dose level 10 mg/d (grade 3 diarrhea and grade 3 laryngopharyngeal infection). The MTD was reached at 7.5 mg/day (dose-level II). The recommended dose of RAD001 was 5 mg/d. After a median follow-up of 22 months, 12 patients are alive, 1 is dead (not related to cancer) and 2 patients had relapsed. Conclusions: Concomitant hormone-radiotherapy and everolimus is well-tolerated with mucositis, hypercholesterolemia, and urinary disorders. The recommended phase-II trial dose of everolimus in this combined setting is 5 mg/day. Clinical trial information: NCT00943956.