ESTRO 38 Abstract book

S793 ESTRO 38

Conclusion Treatment of CRC metastases with SBRT provides a meaningful benefit in PFS with low toxicity. Up to 20% of the patients achieves durable responses. This study supports the implementation of local therapy with SBRT in the multidisciplinary management of mCRC. EP-1463 Radiation dose intensification in rectal cancer: a survey by the AIRO gastrointestinal study group L. Caravatta 1 , M.A. Gambacorta 2 , G. Mantello 3 , M. Lupattelli 4 , M. Di Tommaso 1 , R. Consuelo 1 , G. Macchia 5 , A. De Paoli 6 , R.M. Niespolo 7 , F. Dionisi 8 , M.E. Rosetto 9 , F. Valvo 10 , M.F. Osti 11 , A.G. Morganti 12 , V. Valentini 2 , D. Genovesi 1 1 “SS Annunziata” Hospital- “G. D’Annunzio” University, Radiation Oncology Unit, Chieti, Italy ; 2 Gemelli Advanced Radiation Therapy Center- Fondazione Policlinico Universitario "A. Gemelli"- Catholic University of Sacred Heart, Department of Radiotherapy, Rome, Italy ; 3 State Hospital, Department of Radiotherapy, Ancona, Italy ; 4 University of Perugia and Perugia General Hospital, Radiation Oncology Section, Perugia, Italy ; 5 "Giovanni Paolo II" Foundation- Catholic University of Sacred Heart, Radiotherapy Unit- Department of Oncology, Campobasso, Italy ; 6 Centro di Riferimento Oncologico- National Cancer Institute, Department of Radiation Oncology, Aviano, Italy ; 7 Azienda Ospedaliera S. Gerardo, Department of Radiation Oncology, Monza, Italy ; 8 Azienda Provinciale per i Servizi Sanitari- APSS, Proton Therapy Unit- Department of Oncology-, Trento, Italy ; 9 Ospedale Belcolle, Department of Radiation Oncology, Viterbo, Italy ; 10 Fondazione CNAO, Radiation Oncology Center, Pavia, Italy ; 11 Sant'Andrea Hospital- Sapienza University of Rome, Department of Radiation Oncology, Rome, Italy ; 12 University of Bologna- S. Orsola-Malpighi Hospital, Radiation Oncology Center- Department of Experimental- Diagnostic and Specialty Medicine - DIMES, Bologna, Italy Purpose or Objective Since a dose-response relationship in rectal cancer has been reported, a boost dose to macroscopic disease could represent a potential strategy to improve oncological outcomes in not responder patients after preoperative long-course radiotherapy (LCRT) or to select patients for which organ-preserving strategies might be possible. The Italian Association of Radiation Oncology (AIRO) study group of gastrointestinal malignancies proposed a national survey to investigate boost volume definition, doses and techniques used for dose intensification in preoperative In September 2018, an online survey was produced by a restricted group of recognized experts in rectal cancer. Members of AIRO gastrointestinal study group were individually contacted to request their participation to the survey. An expertise in rectal cancer treatment was required on the basis of the professional experience and their involvement in the multidisciplinary team for rectal cancer treatment. The questionnaire had 25 items focused on: center characteristics (5 items), simulation (3 items), imaging (4 items), volumes and doses (5 items), planning and treatment (8 items). Results Overall, 38 radiation oncologists from different Institutes (north Italy: 25, center: 8, south: 5) joined the study. Twenty-six declared to perform dose intensification preoperative LCRT. The characteristics of patients treated with dose intensification are reported in Table 1. Boost volume is defined as the Gross Tumor Volume (GTV) or as mesorectum area at the level of GTV, with or without additional margins, in 11 (42,31%) and 15 (57,69%) centers, respectively. Boost volume is delineated by LCRT for rectal cancer. Material and Methods

The aim of this study is to analyze the efficacy and safety of treatment with SBRT on metastatic lesions in a cohort

of patients with mCRC. Material and Methods

Retrospective study of patients treated with SBRT on metastatic lesions in different locations between February 2012 and August 2016 at the General University Hospital of Valencia. The variables collected in the study were age, sex, location of the primary tumor, date of surgery, stage of the disease, RAS mutational status , location and number of metastases, type of relapse, treatment with SBRT, number of surgeries and previous chemotherapy lines. Statistical analysis was performed using the statistical package SPSS version 20. Results A total of 49 patients were included (65.5% men). The average age was 70 years. 89.8% of the primary tumors were located in the left colon. 48% of the cases presented mutation in RAS . The distribution by stage at diagnosis was 10.2% for both stages I and II, 20 .4% for III and 59.2% for IV. 83.7% of the metastases were metachronic. 46.9% of the patients were treated with more than 2 chemotherapy lines and 24.5% with ≥ 2 surgeries of metastases before the SBRT treatment. 53.1% of metastatic lesions were located in the lung and 30.6% in the liver. 28.6% of lesions treated with SBRT were the first relapse of the disease. 79.6% of the patients had no metastases in other sites at the time of treatment and 44.9% were treated in more than one lesion. The total dose received in the treatment of SBRT was 45 Gy in 57.4% of the cases (fractionation of 1500cGy/session, 3 sessions, DEB 93.8 Gy) and 22.2% with a dose of 60 Gy. The most frequent adverse events are described in table 1. None of the patients had grade 3-4 events. The median follow-up was 26.1 months. The PFS after treatment with SBRT was 9.9 months (95% IC 4.6 4 - 15.1) and the median OS was 28.9 months (95% IC 19.0 - 38.7). No relapses were observed in 20% of the patients after SBRT. Female sex and chemotherapy treatment before SBRT were significantly associated in the multivariate analysis with worse PFS (HR = 3.5, p = 0.001 and HR = 4.81, p = 0.002).