Salvage radiation therapy after radical prostatectomy: Contribution of a dose escalation to macroscopic local relapses.

Abstract

e634 Background: Salvage radiation therapy (RT) after radical prostatectomy (RP) for prostate cancer using 66 Gy may not be enough to treat macroscopic disease. The presence of a macroscopic nodule on the MRI could justify a focal dose escalation. This study evaluates the tolerance and efficacy of a new technique of irradiation including a focal boost to the nodule. Methods: Between 2011 and 2015, 14 patients, with a macroscopic relapse diagnosed on the MRI, underwent targeted MRI-guided biopsies. Three gold markers were implanted into the prostatic bed for a more accurate MRI/CT fusion and image guided IMRT. A dose of 60 Gy was delivered to the prostatic bed followed by a dose escalation to 72Gy on the macroscopic nodule. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated using the CTCAE v4. PSA level and late toxicities were assessed at 1 month and then every 6 months for 3 years. Results: The mean follow-up was 26.2 [18 – 36] months. Two patients had a biochemical failure after salvage RT (one bone metastasis and one lymph node recurrence). The local control rate was 100% and the biochemical control rate was 85.7%. Results for acute and late toxicities are summarized in the table. One patient presented with grade 2 urinary toxicity during the prostatic bed irradiation which lowered to grade 1 when the dose was focalized to the nodule. No grade 2 acute GI toxicity was seen. All late GI and GU toxicities were grade 1. Conclusions: Dose escalation to the macroscopic nodule visible on MRI is feasible using an IMRT-IGRT approach with gold makers. This technique allows a perfect initial local control at 3 years with a good tolerance. [Table: see text]