ESTRO 36 Abstract Book

S706 ESTRO 36 _______________________________________________________________________________________________

Results All the 125 patients completed the planned treatment, with good tolerance. After RT, the median follow-up was 15 months.Acute toxicities were recorded for the GU [G0=45/125 (36%), G1=63/125 (50.4%); G2=16/125 (12.8%); G3=1/125 (0.8%)], the GI [G0=42/125 (33.6%); G1=72/125 (57.6%); G2=11/125 (8.8%); no G3]. Analyzing data according to RT intent, a higher rate of GU toxicity ≥ 2 was found in the adjuvant setting (17.1%) respect to salvage group (9.8%); p=0.01 at Fisher’s exact text. Furthermore, at statistical analysis no difference was found between the type of surgery (Robotic,Laparoscopic or Open) and incidence of urinary incontinence (p=0.8). The actuarial Kaplan-Meier for biochemical disease free survival (BDFS) were 94% and 77% for adjuvant and salvage RT, at 36 months. Conclusion moderate hypofractionated postoperative RT with VMAT was feasible and safe with acceptable acute GU and GI toxicities. Longer follow-up is needed to assess late toxicity and clinical outcome . EP-1317 PET-guided pelvic re-irradiation for nodal recurrences of prostate cancer P. Dirix 1 , G. De Kerf 1 , B. De Laere 2 , G. Buelens 1 , P. Huget 1 , D. Verellen 1 , P. Meijnders 1 1 Iridium Cancer Network, Department of Radiation Oncology, Antwerp, Belgium 2 Iridium Cancer Network, Translational Cancer Research Unit TRCU, Antwerp, Belgium Purpose or Objective To report our first cases of pelvic re-irradiation using volumetric-modulated arc therapy (VMAT) with a simultaneous integrated boost (SIB) on choline or prostate-specific membrane antigen (PSMA) positron emission tomography (PET) nodal uptake in recurrent prostate cancer, after previous salvage radiotherapy (SRT). Material and Methods Thirteen patients received re-irradiation for a nodal relapse that occurred after initial radical prostatectomy followed by SRT. All patients were initially operated for high-risk prostate cancer between 2007-2014. The initial SRT consisted of radiotherapy of the prostate bed and obturator/iliac lymph nodes to 66.0/52.8 Gy in 33 fractions of 2.0/1.6 Gy, respectively, through intensity- modulated radiotherapy (IMRT). All patients had a consequent pelvic nodal relapse on choline (n = 6) or PSMA (n = 7) PET-CT, without extra-pelvic disease. The location of the pelvic recurrences is shown (Figure). The mean PSA at time of nodal recurrence was 2.94 µg/L (range, 0.6 – 7.89 µg/L). Patients were deemed unfit for surgery and/or surgically inoperable. The re-irradiation was initiated a mean 46 months (range, 8 – 107 months) after SRT. All patients received 66.0/50.0 Gy in 25 fractions of 2.64/2.0 Gy to the PET-positive lymph nodes and elective pelvic nodal regions, respectively. Underdosage of the elective planning target volume (PTV) was allowed (taking the earlier SRT into account), but not of the high-dose PTV. No androgen-deprivation therapy (ADT) was initiated. All toxicity was prospectively scored according to the common toxicity criteria (CTC) version 4.0. Results Acute toxicities were limited: no gastro-intestinal (GI) nor genito-urinary (GU) acute toxicities ≥ grade 2 were observed. Two patients suffered from mild grade 1 diarrhea until 2-3 weeks after radiotherapy, no acute GU toxicities were observed. There was a mean follow-up of 17 months (range, 6 – 27 months) since re-irradiation. Regarding late toxicity, one patient developed grade 1 hematuria at 1 year after re-irradiation which was due to pathologically confirmed cystitis. No other late GI or GU

toxicities were observed. Regarding oncological outcome, all patients developed an initial PSA response, defined as a decline from baseline in PSA level of 80% or greater. Currently, 11 patients remain controlled (without ADT) at a mean of 16 months (range, 6 – 27 months) after re- irradiation, with a mean PSA of 0.34 µg/l (range, 0.17 – 0.63 µg/L). Two patients progressed within 6 months after the end of radiotherapy and currently receive (chemo- )hormonal treatment. Interestingly, these 2 patients had a PSA doubling time < 6 months. All the other patients had a PSA doubling time > 11 months.

Conclusion Pelvic re-irradiation with SIB to the PET-based nodal recurrences is a safe and promising alternative to pelvic lymph node dissection. However, patient selection is crucial and could in the future be guided by biomarkers. Also, concomitant ADT should now be considered based on GETUG-AFU 16. EP-1318 Is hypofractionation combined to WPRT effective in high risk prostate cancer patients? N.G. Di Muzio 1 , A. Fodor 1 , C.L. Deantoni 1 , B. Noris Chiorda 1 , S. Broggi 2 , P. Mangili 2 , I. Dell'Oca 1 , A. Chiara 1 , P. Passoni 1 , N. Slim 1 , M. Pasetti 1 , R. Calandrino 1 , C. Cozzarini 1 , C. Fiorino 1 1 San Raffaele Scientific Institute, Department of Radiotherapy, Milano, Italy 2 San Raffaele Scientific Institute, Medical Physics, Milano, Italy hypofractionation to prostate/seminal vesicles only cannot be regarded as a standard in intermediate and high-risk prostate cancer. We report here the 5 and 7 year clinical outcomes in high risk (HR) prostate cancer (PCA) patients (pts) treated with hypofractionated TomoTherapy (HT) and routine irradiation of pelvic lymph-nodes (PLN). Material and Methods From April 2006-August 2015, 115 HR PCa pts were treated with HT, within a phase I-II study. The dose to PLN, was 51.8 Gy(1.85 Gy/fr), with simultaneous integrated boost (SIB), to prostate and seminal vesicles, up to 74.2Gy in 28 fr (2.65Gy/fr). Androgen deprivation therapy (ADT) was prescribed to 104/115 pts for a median of 26 (3-120) months (mos). Median age was 75 (57-90) years, median Gleason Score was 8 (5-10), median initial PSA was 12.4 (1.7-206.0) ng/mL; clinical T stage was: T1c-T2a in 62 pts, T2b-T2c in 35 pts, T3a-T3b in 17 pts and T4 in 1 patient. Results With a median follow up of 68 (2-121) months, 19 pts (16.5%) exhibited a biochemical relapse after a median interval elapsed from the HT end of 64 (2-117) months. Purpose or Objective Several recent studies have concluded that