ESTRO 2021 Abstract Book

S1005

ESTRO 2021

Conclusion Adjuvant hypofractionated RT concomitant to capecitabine in bile duct carcinoma is feasible with a good toxicity profile. Grading and margin status were the main predicting outcome factors. Neo/adjuvant ChT can explain the similarity between pT1-T2/pT3-T4 and pN0/pN+ in term of outcome The trend in favour of R0 in term of TTDP and OS while the no difference in term of TTLP suggests to consider RT in neoadjuvant setting to improve post-operative R0. PO-1213 Radiomics in the assessment of response after pancreatic SBRT: a pilot study C. De La Pinta 1 , M. Muñóz 2 , C. Picón 2 , R. Fuentes 3 , C. Guillén 3 , D. Sevillano 4 , M. Martín 5 , I. Mayorga Ruiz 6 , P. Moreno Ruiz 7 , A. Jiménez Pastor 8 , J.M. Molina Villar 9 , S. Sancho García 5 1 Ramon y Cajal Hospital-IRYCIS, Radiation Oncology, Madrid, Spain; 2 Ramón y Cajal Hospital, Radiology, Madrid, Spain; 3 Ramón y Cajal Hospital, Medical Oncology, Madrid, Spain; 4 Ramon y Cajal Hospital, Medical Physics, Madrid, Spain; 5 Ramón y Cajal Hospital, Radiation Oncology, Madrid, Spain; 6 Quibim, Head of Discovery Unit , Valencia, Spain; 7 Quibim, Clinical Trial Assistant, Valencia, Spain; 8 Quibim, ., Valencia, Spain; 9 Ramón y Cajal Hospital, Surgery, Madrid, Spain Purpose or Objective The aim of the study is to evaluate the predictive power of CT-based radiomic features before and after SBRT therapy in pancreatic adenocarcinoma. Materials and Methods The patient cohort included 9 pancreas adenocarcinoma patients. Radiomic texture features were extracted from computed tomography (CT) images obtained for the gross tumour volume pre-SBRT and in the follow- up. Quibim® software was used to extract 13 radiomic CT features that reflect tumour heterogeneity, including shape, asymmetry, energy, grey level non-uniformity, grey level concurrence matrix, grey level dependence matrix, entropy, variance and occupancy, among others. Radiomic variables were correlated with clinical variables including age, size, ECOG, stage, tumour markers, location and previous treatment. Results A clinical-radiomic signature associated with local control (LC) was found significant in training sets. Younger age (concordance index 0.71), larger tumour size (concordance index 0.669) and more irregular tumours (concordance index= 0.636) were associated with longer time to local control (>20 months). The model showed a significant ability to discriminate between patients treated with neoadjuvant (p=0.01) and adjuvant (p=0.007) chemotherapy and patients treated with only SBRT. Conclusion Radiomics may be a suitable tool for the assessment of response to treatment after SBRT. This is a pilot study that allows to establish hypotheses for future prospective studies including a larger number of patients. PO-1214 Toxicity profile of adjuvant hypofractionated Image-Guided Radiotherapy in biliary tract carcinoma N. SLIM 1 , P. Pacifico 1 , P. Passoni 1 , R. Tummineri 1 , M. Ronzoni 2 , F. Pedica 3 , C. Fiorino 4 , A.M. Deli 1 , A. Casadei Gardini 2 , S. Cascinu 2 , F. De Cobelli 5 , L. Aldrighetti 6 , N.G. Di Muzio 7 1 IRCCS San Raffaele Scientific Institute, Radiation Oncology, Milan, Italy; 2 IRCCS San Raffaele Scientific Institute, Medical Oncology, Milan, Italy; 3 IRCCS San Raffaele Scientific Institute, Anatomical Pathology, Milan, Italy; 4 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 5 IRCCS San Raffaele Scientific Institute, Radiology, Milan, Italy; 6 IRCCS San Raffaele Scientific Institute, Surgery, Milan, Italy; 7 IRCCS San Raffaele Scientific Institute, Vita e Salute University, Radiation Oncology, Milan, Italy Purpose or Objective Adjuvant radiochemotherapy is controversial in patients (pts) with biliary tract carcinoma. We previously tested hypofractionated IGRT in pts with locally advanced pancreatic cancer. We update our results regarding toxicity outcome using the same hypofractionated RT schedule in adjuvant setting in bile duct carcinoma. Materials and Methods Pts with intra, extra-hepatic or gallbladder cancer were treated. Simulation consisted in contrast-enhanced computed tomography (c-e-CT) or FDG CTPET, 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. Prescription dose was 40- 44.25 Gy (EQD2=50- 54 Gy) in 15 fractions with SIB up to 50 Gy to R1 or positive CTPET sites when it was possible respecting dose constraints to OARs. The radiation treatment was delivered with VMAT or tomotherapy concomitant to capecitabine (CAPE). Results From 05/2009 to 07/2020, 57 pts (32 M; 25 F) were treated. Median age: 68 years (45-86). Twenty-six pts (46%) had Klatskin tumor, 17 pts (30%) common or distal bile duct carcinoma, 7 pts (12%) intrahepatic carcinoma and 7 pts (12%) gallbladder carcinoma. The pathological staging was T1-T2 in 30 pts (53%), T3-T4 in 27 (47%), 28 pts were pN0 (49%), 25 pts were pN+ (44%) and 4 pts were pNx (5%), 38 pts (67%) were R1, 19 pts (33%) were R0. Grading was G1 in 5 pts (9%), G2 in 36 pts (63%) and G3 in 16 pts (28%). Five pts (9%) received neoadjuvant ChT with GEM+CDDP scheme, median number of cycles was 6 (6-9). Twenty-two pts (39%) received different schemes of adjuvant ChT (11 CDDP+GEM, 2 PEXG, 2 GEMOX, 1 GEM, 1 CAPE), median number of cycles was 6 (4-12). Forty-three pts (75%) received capecitabine concomitant with RT. Twenty-six pts (46%) underwent c-e-CTPET simulation, 14 pts (25%) were PET positive, 6 pts (43%) of whom who were also R1 received SIB from 48 Gy to 50 Gy. Thirty-five pts (61%) were treated with tomotherapy and 22 (39%) with VMAT. The average PTV was 387 cc (110-861) and the average PTV of SIB was 49 cc (28.5- 80). At a median follow up of 21 months (2-118) median Overall survival of all population was 31 months and 53 pts (93%) were evaluable for acute and late toxicity. G1-G2 acute toxicity occurred in 36 pts (69%) (G1 27 pts; G2 9 pts). No acute G3 or G4 toxicity was recorded. G1-G2 late toxicity occurred in 8 pts (14%) (G1 5 pts; G2 3 pts). The most common symptoms were diarrhea, nausea/vomiting, abdominal pain and cholangitis. Only 5 pts (9%) had