ESTRO 36 Abstract Book

S705 ESTRO 36 _______________________________________________________________________________________________

with prophylactic TT on LN areas (pelvic/lombo-aortic, LA) and simultaneous integrated boost(SIB) on PET+ LN. Material and Methods From March 2007-May 2013, 36 PCa pts treated with radical prostatectomy (RP) +/- pelvic/LA LN dissection(LND), and presenting +LN at PET, were treated with TT. Analysis was restricted to oligometastatic treatment-naïve PCa pts satisfying published selection criteria for SBRT (Ost et al, Eur Urol 2016), including also castration resistant and >3 +LN pts (worse prognosis). Pts characteristics were: median age 67(53-78) yrs; median PSA post-surgery/at relapse: 2.74(0.66-23.52) ng/ml; median Gleason score 8(6-10). Five pts underwent RP; 33 RP+LND. Twelve pts were pT2, 22 pT3, 1 pT4, 11 pN1, 1 M1a, 11 R1. Twenty one pts had androgen deprivation(AD) prescription after surgery, 5 were hormonal resistant; 1 patient was treated with chemotherapy(Docetaxel and Estramustine). The interval between surgery and PET was 19.3(3.1-170.2) mts, the median number of PET +LN was 3(1-20). In 23 pts AD was prescribed for a median of 19(0- 57) mts. Patients were treated with daily image-guided TT on pelvic/LA LN (51.8 Gy/28 fr), with simultaneous integrated boost (SIB) on prostatic bed (71.4 Gy), and on PET+ LN (65.5 Gy). Results With a median follow up of 38.1(14.4-82) mts, acute toxicity was low (1 G3 GU acute toxicity;2 G2 bowel, 2 G2 rectal and 2 G2 GU acute toxicities). Late toxicities were: rectal ³ G2 13.9% (1 pt G3), lymphedema ³ G2 13.9% (1 pt needing surgery), and GU ³ G2: 33.4% (1 pt with salvage cystectomy). At the last control, late toxicities were mild, showing that most events were transitory with no rectal G2, 1 rectal G3; 2 GU G2, 3 GU G3 and 2 Lymphedema G2. A summary of outcome is shown in Table I and Figure I: Median biochemical relapse free survival (BRFS) was 51.2 months; 3 and 5-year biochemical relapse-free survival (bRFS) was 65.5% and 43% respectively; distant progression free survival (DPFS) was 88% and 70% and Cancer Specific Survival was 92 and 83%.

Conclusion Our excellent outcome results suggest that PET-guided prophylactic treatment of LN chains together with SIB to PET+ LN may translate in a substantial increase of bRFS and DPFS compared to reported results after SBRT. A phase III trial comparing these approaches would be suitable. Because of high GU toxicity caused by hypofractionation on post-operative settings the protocol for prostate bed irradiation was modified since 2014 to deliver 70-74 Gy with conventional fractionation. EP-1316 Moderate Hypofractionation RT in post- prostatectomy setting:report on feasibility and acute toxicity S. Fersino 1 , U. Tebano 1 , R. Mazzola 1 , F. Ricchetti 1 , N. Giaj Levra 1 , A. Fiorentino 1 , G. Sicignano 1 , S. Naccarato 1 , R. Ruggeri 1 , F. Alongi 1 1 Sacro Cuore Don Calabria Cancer Care Center, Radiation Oncology, Negrar, Italy Purpose or Objective to evaluate the acute toxicity profiles of a moderate hypo- fractionated regimen with volumetric modulated arcs therapy (VMAT) in prostate cancer (PC) patients underwent to radical prostatectomy (RP). Material and Methods From December 2012 to February 2016, 125 patients, previously submitted to RP, received adjuvant (64 patients) or salvage (61 patients) radiotherapy (RT) inside an institutional protocol of moderate hypofractionation schedule using VMAT technique (Varian RapidArc, Palo Alto, CA, USA).Eligible patients were < 85 years old, with an ECOG performance status of 0–2, histologically proven adenocarcinoma of the prostate without distant metastases, and pathological stage pT2–4 N0-1, with at least one of the following risk factors: capsular perforation, positive surgical margins, seminal vesicle invasion and/or postoperative PSA > 0,2 ng/ml.Patients were stratified into low (1%), intermediate (9%), and high- risk (90%) groups.The median age was 68 years. The median doses were 66 Gy (range 65.5-71.4) to the prostatic bed and 52.5 Gy (range 50.4-54) to the pelvic lymph nodes, in 28 or 30 fractions. The acute genitourinary (GU) and gastrointestinal (GI) toxicities were scored according to the Common Terminology Criteria for Adverse Events CTCAE v4