ESTRO 36 Abstract Book

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acceptable, although a longer follow-up is needed to evaluate long-term outcome and toxicities. PO-0727 Acute intestinal toxicity after whole-pelvis IMRT for prostate cancer from the patient’s perspective B. Noris Chiorda 1 , E. Garibaldi 2 , B. Saracino 3 , D. Cante 4 , B. Avuzzi 5 , E. Villa 6 , J.M. Waskiewicz 7 , M. Gaetano 8 , F. Munoz 9 , G. Girelli 10 , C. Sini 11 , T. Rancati 5 , F. Badenchini 5 , C. Bianconi 1 , C. Fiorino 11 , C. Cozzarini 1 1 San Raffaele Scientific Institute, Radiotherapy, Milan, Italy 2 Istituto di Candiolo - Fondazione del Piemonte per l'Oncologia IRCCS, Radiotherapy, Candiolo TO, Italy 3 Istituto Nazionale Tumori "Regina Elena", Radiotherapy, Rome, Italy 4 Ospedale Civile ASL TO4, Radiotherapy, Ivrea, Italy 5 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy, Milan, Italy 6 Humanitas Gavazzeni, Radiotherapy, Bergamo, Italy 7 Comprensorio Sanitario di Bolzano, Radioterapia, Bolzano, Italy 8 Centro Aktis, Radiotherapy, Marano NA, Italy 9 Ospedale Regionale 'U. Parini' - AUSL Valle d'Aosta, Radiotherapy, Aosta, Italy 10 Ospedale degli Infermi ASL BI - Biella, Radiotherapy, Biella, Italy 11 San Raffaele Scientific Institute, Medical Physics, Milan, Italy Purpose or Objective The aim of this study was to thoroughly analyze patient- reported acute intestinal toxicity (IT) from whole-pelvis RT delivered by means of modern IMRT techniques (IM- WPRT). Material and Methods A multi-Institutional, observational study registered at ClinicalTrials.gov was started in 2014 with the aim of assessing Intestinal, Hematological and Urinary toxicity from IM-WPRT for prostate cancer. Acute IT is evaluated by means of the 10 items of the Inflammatory Bowel Disease Questionnaire pertaining to the Bowel Domain (IBDQ-B) administered to patients (pts) at baseline and at RT mid-point and end: bowel movements (item #1), loose bowel movements (#5), abdominal cramps (#9) and pain (#13), gas passage (#17), bloating (#20), rectal bleeding (#22), urgency to defecate (#24), accidental soiling (#26), nausea and feeling sick (#29). Each item is scored on a 1- 7 point scale (most severe symptoms=lower scores). Analyses were performed on the worst variations (Δ) of each item between baseline and RT mid-point or end. This analysis pertains to 242 pts with complete data at all the 3 time intervals, treated with adjuvant, salvage or radical intent (n=91, 104 and 47, respectively), with VMAT, Tomotherapy or static-field IMRT (n=122, 90 and 30, respectively). RT was delivered at conventional (CF, 1.7-2 Gy/fr,n=92) or moderate hypo-fractionation (HYPO, 2.15- 2.65 Gy/fr, median 2.35 Gy/fr, n=114). The median EQD2 (for α/β=3) to prostatic bed and prostate were 72.6 and 77 Gy, respectively; pelvic lymph-nodes/pelvic lymph- nodal area were always treated with conventional fractionation (range 50.4-56.1 Gy, median 51.8; daily dose: 1.7-2 Gy/fr). Results Overall, IM-WPRT was well tolerated, with a median Δ with respect to baseline of -2 points for item #1, of -1 points for items # 5, 17 and 24, and 0 for the 6 remaining items (Table 1, Fig. 1). Moreover, the consequent impairment of Emotional, Social and Systemic Domains evaluated by the IBDQ was exceptionally mild (Table 1). Nevertheless, the Δ of all the 10 IBDQ-B at RT end with respect to baseline was always statistically significant (p≤0.02) at the Analysis of Variance (ANOVA). Interestingly, in the 134 patients with complete data at 1 year, ANOVA highlighted a persisting, significant (p≤0.04) Δ with respect to baseline

Results The median follow-up was 33 months (range 2-68). The 5- year biochemical disease-free survival (bFDS) rate was 90% and overall survival (OS) was 86%. Acute genitourinary (GU) toxicity grade 1 and 2 were 37% and 12% respectively, but only 8 patients (2.4%) experienced acute urinary retention (Grade 3). Acute gastrointestinal (GI) toxicity grade 1 and 2 were 16% and 6% respectively. No grade 3 or 4 GI toxicity was observed. Late GU toxicity ≥ grade 3 included 7 patients (2.1%), and the incidence of late GI toxicity ≥ grade 3 was 1% (3 patients) compatible with rectal radiation proctopathy, as is showed in figure1.

Conclusion Dose escalation with a single-fraction HDRB is feasible and well tolerated. The profile of acute and late toxicity is