Abstract Book

S857

ESTRO 37

Purpose or Objective In a recent publication we have reported excellent biochemical Relapse Free Survival (bRFS) in prostate cancer (PCa) patients (pts) treated with hypofractionated tomotherapy (HTT) with simultaneous integrated boost (SIB) in a mono-institutional prospective study. Here we report the results in high-intermediate, high and very high-risk PCa pts. Material and Methods From April 2006 to July 2014 190 PCa pts with median age 75 (54-90) years were treated with HTT on pelvic lymph nodes (including common iliac chain) to a total dose of 51.8 Gy, with SIB on prostate and seminal vesicles to 74.2 Gy (88 Gy equivalent 2 Gy dose for a/b=1.5) in 28 fractions delivered in 5 ½ weeks. Ninety-three pts presented high-intermediate risk (at least 2 intermediate risk factors: GS 7, PSA≥ 10 < 20 ng/ml, stage ≥ T2b) and 97 high- risk/ very high risk (one or >1 high risk factors: GS≥8, iPSA≥ 20 ng/ml, stage ≥ T3) PCa. Androgen deprivation therapy (ADT) was prescribed to 161/190 pts for a median of 26 (1-120) months (mos). Median initial PSA was 11.03 (1.68-340.79) ng/mL.N1/N2 and M1 patients were excluded. Results With a median follow up of 61 (12-121) mos, 5 year- overall survival (OS) was 86.9%, with high probability of dying from other causes (11%), and a low probability of dying from cancer (1.6%). Five year bRFS was 90.9%, while disease free survival (DFS) was 93.3 %, for both groups. There was no significant difference between high-intermediate and high/very-risk pts in terms of OS, bRFS and DFS at 5 and 10 years. There was statistically significant difference between the onset time of late G2 (14.2 mos) and G3 (27.8 mos) toxicity (p= 0.046). A longer duration of ADT (>36 months) was associated with decreased survival (p<0.001), for two reasons, first because pts who relapsed during ADT(worse prognosis) continued LHRH in association with other therapies, and second due to the toxicity of long-term hormonal therapy. Log-rank test showed significant difference between T1/T2 stage and T3/T4 stage when examining OS(p=0.037) and between GS lower than 4 and GS 4/5 for bRFS only(p=0.018). In a Cox multiple regression model, after stepwise selection, nadir of PSA at 6 months after HTT (p<0.001) and T3/T4 stage (p=0.014) were predictive for bRFS. Similar results were found when examining DFS as outcome (nadir of PSA at 6 months after HTT, p=0.004 and T3/T4 stage, p=0.011). Conclusion Excellent 5-year biochemical control, of more than 90%, can be obtained in high-intermediate and high-risk PCa pts treated with extensive pelvic prophylactic HTT and high-dose SIB on prostate. T stage and PSA nadir at 6 months were predictive for disease biochemical control, distant progression and survival. EP-1594 Analysis of urinary toxicity by uroflowmetry in hypofractionated radiotherapy after prostatectomy S. Saldi 1 , S. Chierchini 2 , M. Mendichi 2 , V. Lancellotta 2 , R. Bellavita 1 , I. Palumbo 2 , T. Dipilato 3 , V. Bini 4 , C. Aristei 2 1 Santa Maria della Misericordia Hospital, Department of Radiation Oncology, Perugia, Italy 2 University of Perugia, Radiation Oncology Section, Perugia, Italy 3 Santa Maria della Misericordia Hospital, Medical Physics Department, Perugia, Italy 4 University of Perugia, Internal Medicine -Section of

cancer after RP ± lymphadenectomy and candidates for SRT. All patients performed 68 Ga-PSMA PET/CT before SRT. In case of PSA >1 ng/ml, patients underwent first 18 F- choline PET/CT and if negative 68 Ga-PSMA PET/CT. All focal abnormal uptakes higher than background at 68 Ga-PSMA PET/CT were considered as positive findings for disease. Dubious findings were explored by other imaging techniques (CT scan, MRI) and defined as true positive or true negative by a multidisciplinary consensus. In case of negative 68 Ga-PSMA PET/CT or local relapse, patients were sent to standard SRT. In case of lymph nodes relapse or distant metastases the management was modified on the basis of 68 Ga-PSMA PET/CT findings. Association between PET positivity and clinical patterns was evaluated by Fisher’s exact test. Results A total of 50 patients (median age 70y, range 56-81) were enrolled. Patological T stage was T1c-T2b-c in 31 patients (62%), T3a-b in 16 patients (32%) and not reported for 3 patients. Gleason Score (GS) was ≤7 in 37 patients (74%), ≥8 in 12 patients (24%) and not reported for 1 patient. Persistent or biochemical recurrence (BCR) prostate cancer were found in 13 (26%) and 37 (74%) patients, rescpectively. Median time of BCR was 29 motnhs (range 4-96 months). Median PSA value at the moment of 68 Ga-PSMA PET/CT was 0,45 ng/ml (range 0,23-8,9) with a median PSA doubling time (DT) and PSA velocity of 6,87 moths (range 0,6-264,8) and 0,4 ng/ml/y (range 0-30,2), respectively. 68 Ga-PSMA PET/CT was positive in 11/50 patients (20%). According to PSA level 68 Ga-PSMA PET/CT was positive in 5/28 patients with PSA >0,2 and ≤0,5 ng/ml, in 2/14 patients with PSA >O,5 e ≤1, in 2/5 patients with PSA >1 e <1,5 ng/ml and in 2/3 with PSA ≥1,5 ng/ml. Pattern of recurrence was in 1 patients only on prostate bed and in 10 patients in lymph nodes (in 1 case also with single bone lesion and in 1 case also with prostate bed recurrence). PET positivity was found significantly associated with T ≥3 stage (p= 0,029) and significantly correlated with low PSA DT (p = 0,015; 3.1 in PET+ vs 8,7 months in PET -) and high PSA velocity (p= 0,020; 0,8 in PET + vs 0,4 ng/ml/yr in PET-). Patient management on the basis of 68 Ga-PSMA PET/CT findings was modified in 9 cases. Conclusion Preliminary data suggest that 68 Ga-PSMA PET/CT can be clinically useful to guide the treatment strategy in patients with persistent or recurrence prostate cancer after RP. In this setting a good selection of the patients that could benefit of 68 Ga-PSMA PET/CT before SRT is mandatory. However, larger prospective trials are needed. N.G. Di Muzio 1 , C.L. Deantoni 1 , C. Brombin 2 , C. Cozzarini 1 , S. Broggi 3 , P. Mangili 3 , M.S. Di Serio 2 , I. Dell'Oca 1 , A. Chiara 1 , R. Calandrino 3 , C. Fiorino 3 , A. Fodor 1 1 San Raffaele Scientific Institute, Department of Radiotherapy, Milano, Italy 2 Vita-Salute San Raffaele University, University Center for Statistics in the Biomedical Sciences, Milano, Italy 3 San Raffaele Scientific Institute, Medical Physics, Milano, Italy EP-1593 Hypofractionated IGRT in high-intermediate and high/very-high risk prostate cancer patients