ESTRO 37 Abstract book

S859

ESTRO 37

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 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 EP-1593 Hypofractionated IGRT in high-intermediate and high/very-high risk prostate cancer patients

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 internal Medicine and Metabolic and Endocrine Disease-, Perugia, Italy Purpose or Objective According to an estimated 1.5 Gy alpha/beta ratio prostate cancer may be more sensitive to hypo- fractionated radiotherapy (Hypo-RT) than conventional schedule.Several phase III clinical trials exploring hypofractionation in localized prostate cancer showed no significant differences in clinical outcomes, efficacy and tolerance to conventional RT , while randomized data in support of hypofractionated radiotherapy after radical prostatectomy are lacking. Most trials administered the IPSS questionnaire to evaluate GU toxicity. We designed a prospective observational study to investigate Hypo-RT in adjuvant and salvage prostate cancer patients with the aim of evaluate acute and late genitourinary (GU) toxicity with uroflowmetry. Material and Methods Between March 2013 and October 2016, 112 patients were enrolled in the study. All had undergone Radical Prostatectomy. Hypofractionated adjuvant-RT ( 2.25 Gy daily for 29 fractions; a total 65.25 Gy) was administered to 40 patients with high risk features . Hypofractionated salvage-RT (2.25 Gy daily for 32 or 33 fractions; total 72 -74.5 Gy) was prescribed for 72 patients with biochemical/local recurrence.Most patients had uroflowmetry before starting RT. Uroflowmetry was repeated at different time-points of the follow-up and the result at the latest follow-up was used in the statistical analysis. Results No patient in either group was affected by GU-grade 3 toxicity at a median follow up of 18 months . 37 (92,5%) and 65 (90%) patients submitted to adjuvant and salvage