ESTRO 38 Abstract book

S834 ESTRO 38

EP-1546 Stereotactic radiotherapy for prostate bed recurrence after prostatectomy, a multicentric series G. Francolini 1 , B.A. Jereczek-Fossa 2,3 , V. Di Cataldo 4 , G. Simontacchi 1 , G. Marvaso 3 , M.A. Zerella 2,3 , C.I. Fodor 3 , L. Masi 4 , L. Livi 5 1 Azienda Ospedaliero Universitaria Careggi, Radiotherapy, Florence, Italy ; 2 University of Milan, Department of Oncology and Hemato-oncology, Milan, Italy ; 3 IEO European Institute of Oncology- IRCCS, Division of Radiotherapy, Milan, Italy ; 4 Istituto Fiorentino di Cura ed Assistenza, CyberKnife Center, Florence, Italy ; 5 Department of Experimental and Clinical Biomedical Sciences- University of Florence, Radiotherapy Unit, Florence, Italy Purpose or Objective Rate of biochemical recurrences in men affected by localized prostate cancer after radical prostatectomy (RP) ranges between 20 and 50%. Risk is particularly high for positive margins and poorly differentiated disease. Biochemical recurrence can be managed with curative purpose through salvage radiation therapy (SRT). However, Progression-free survival after conventional SRT approach, without concomitant androgen deprivation therapy (ADT), is 56% at 5 years. Moreover, likelihood of treatment failure in patients with pre-RT PSA values greater than 1.5 ng/ml is high, with PFS at 5 years of 18%. Positive metabolic imaging detecting local recurrence negatively impacts outcomes after SRT in this setting. Data from literature suggest that higher relapse-free survival is achieved by increasing radiation dose in patients undergoing SRT. Thus, when macroscopic recurrence is detected in prostatic bed through diagnostic imaging (MRI or CT-PET scan) improved local control may be achieved by extremely hypofractionated regimens. Here we present results from a multicentric retrospective experience including patients affected by macroscopic prostate bed recurrence and treated with stereotactic radiotherapy Material and Methods Data of 71 patients with prostate bed macroscopic recurrence treated in two institutions in Italy were reviewed. Recurrences were detected by MRI or CT-PET. Patients underwent stereotactic radiotherapy on prostate bed recurrence with a mean dose of 34.4 Gy (32.5-35 Gy) in 5 fractions, using Brainlab Vero R or Cyberknife R systems. Patients features, clinical outcomes and adverse events were reported. Biochemical failure after treatment was defined as increase of PSA levels of >10% if compared to pre-treatment value. Complete biochemical response after treatment was defined as PSA nadir <0.2 ng/ml. Univariate and multivariate analysis was performed through Cox regression model to explore the association between prognostic factors (Gleason score

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Results 71 patients were included, 16.9% were under ADT during treatment. Gleason score >7 and stage pT3 at diagnosis were reported in 26,8 and 45% of patients, respectively. Mean PSA at recurrence was 2,3 ng/ml, mean time to recurrence after RP was 98,6 months. Average volume of GTV was 10,8 cc (0,7-34,6). After an average follow up of 21.5 months 73