ESTRO 2020 Abstract Book

S555 ESTRO 2020

evaluated by CTCAE v4.0 scale. Survival curves were assessed by Kaplan-Meier method. For hypothesis testing, an equivalence and a non-inferiority test was calculated. Results At univariate analysis no statistically, significant differences based on the matching criteria and acute and late toxicities, were recorded. No statistically significant differences were recorded even in terms of OS, DFS, and DMFS between the two cohorts. Median, 1-, and 2-year LC were: 16.0 months, 53.1%, 40.5% and 22.0 months, 80.4%, 49.8% (p= 0.017), for RCT cohort and SBRT cohort, respectively. A statistically non inferiority significance in terms of OS between RCT and SBRT was recorded ( 95% CI: 2.24, p= 0.031).

3 months post treatment. The Cox regression model was used for multivariate analysis. Results Spearman correlation coefficient was 0.551, which showed gradual shrinking of esophageal tumor volume from the beginning of radiotherapy to three months post treatment. General linear model repeated measures showed that reduction of GTVe was predominant during the first 20 fractions of radiotherapy. Age, pre-treatment GTVe, GTVe 3months post treatment and GTVe RR at 20 th fraction of radiotherapy were all significantly associated with OS on univariate analysis. Gender was correlated with LRRFS on univariate analysis. Multivariate analysis showed that GTVe ≤20cc, GTVe RR at 20 th fraction of radiotherapy ≥35% were positive predictive factors of OS. Patients with pre-treatment GTVe ≤20cc had favorable LRRFS. Conclusion GTVe and volume reduction ratios by time are reliable prognostic factors for treatment outcomes of esophageal cancer treated with definitive CRT. Patients with GTV<20cc, GTVe reduction ratio at 20 th fraction of radiotherapy ≥ 35% demonstrated prolonged OS. PO-1044 Postoperative hypofractionated Image-Guided IMRT concomitant to chemotherapy in biliary tract cancer N. Slim 1 , R. Tummineri 1 , P. Passoni 1 , A. Fasolo 2 , A.M. Deli 1 , L. Aldrighetti 3 , N. Di Muzio 1 1 San Raffaele Scientific Institute, Radiation Oncology, Milan, Italy ; 2 San Raffaele Scientific Institute, Medical Oncology, Milan, Italy ; 3 San Raffaele Scientific Institute, Surgery, Milan, Italy Purpose or Objective Adjuvant radiochemotherapy is controversial in patients (pts) with bile duct carcinoma but suggested in R1, lymph nodes (LNs) positive or stage ≥ T2. We previously tested hypofractionated IGRT in pts with locally advanced pancreatic cancer (Int J. Rad. Onc. Biol. Phy, Vol. 87, 2013). We report our experience using the same hypofractionated RT schedule in adjuvant setting in biliary tract carcinoma. Material and Methods Pts with intra, extra-hepatic or gallbaldder cancer were treated. Simulation consisted in contrast-enhanced computed tomography (c-e-CT) or FDG CTPET or 4D c-e- CT, CTV included surgical bed and regional LNs taking into account tumor site. PTV was defined adding standard margins (1, 1, 1.5 cm) to CTV or 0.5 cm in pts who underwent 4D c-e-CT. Prescription dose was 40- 44.25 Gy in 15 fractions with SIB up to 50 Gy to R1 or positive CTPET sites respecting dose constraints to OAR delivered with VMAT or tomotherapy concomitant to capecitabine (cape). Results From 05/2009 to 04/2018, 40 pts (25 M; 15 F) were treated. Median age: 69 years (45-83). Twenty-one pts (52.5%) had Klatskin tumor, 11 pts (27.5%) common or distal bile duct carcinoma, 5 pts (12.5%) intrahepatic carcinoma and 3 pts (7.5%) gallbladder carcinoma. After surgery 28 pts (70%) were R1, 12 pts (30%) were R0 (3: N+, 4: pT3N+, 2: pT4, 1: hepatic hilus infiltration, 2: after surgery for local relapse). Four pts (10%) were previously treated with neoadjuvant ChT (3: GEM+CDDP, 1: cape). Fourteen pts (35%) received adjuvant ChT (7: CDDP+GEM, 2: GEMOX, 2: PEXG, 1: GEM, 1: cape, 1: CBDCA+ VP16). Twenty-seven pts (67.5%) received concomitant ChT. Simulation was performed with c-e-CT and CTPET in 16 pts (40%), with 4D c-e CT in 6 pts (15%) and with c-e-CT in 18 pts (45%). Twelve pts (75%) were PET positive. Twenty- four pts (60%) were treated with tomotherapy and 16 (40%) with VMAT. All pts were evaluable for acute toxicity, it was G1-G2: 3 pts (7.5%) diarrhea, 19 (47.5%) nausea/vomiting, 8 (20%) abdominal pain, 3 (7.5%) cholangitis, 1 (2.5%) gastric ulcer. Only 2 pts (5%) had G3 late toxicity (1: gastric

Conclusion Our analysis demonstrated that SBRT is comparable to RCT in terms of clinical outcomes and yet convenient for the patients due to its short duration. Therefore, our study seems to justify randomized studies to compare SBRT +/- CHT and RCT PO-1043 Reduction ratio of tumor volume is predictive factor in esophageal carcinoma undergoing SMART R. Huang 1 , H. Guo 1 , J. Chen 1 , T. Zhai 1 , J. Chen 2 , K. Lin 3 , Z. Chen 4 , D. Li 1 , C. Chen 1 1 Cancer Hospital of Shantou University Medical College, Department of Radiation Oncology, Shantou, China ; 2 Cancer Hospital of Shantou University Medical College, Department of Radiology, Shantou, China ; 3 Shantou University Medical College, Department of Health Statistics, Shantou, China ; 4 University of Hong Kong- Shenzhen Hospital, Department of Radiation Oncology, Shenzhen, China Purpose or Objective The aim of this study is to assess the value of serial computed tomography(CT) scans before, during and after treatment in predicting survival of esophageal cancer(EC) patients treated with simultaneous modulated accelerated radiotherapy combined with 53 patients with histologically confirmed esophageal cancer treated with SMART were included for analysis. Gross tumor volume of esophagus (GTVe) was manually contoured on the CT images before treatment, at 20th fraction of radiotherapy, at completion of treatment and 3months post treatment. GTVe reduction ratio was calculated to reveal changes of tumor volume by time. The Kaplan-Meier method was used to estimate overall survival, loco-regional recurrence free survival and for univariate analysis. Spearman correlation coefficient was calculated to study linear association in GTVe reduction ratio from the beginning of radiotherapy to chemotherapy(SMART). Material and Methods