ESTRO 2020 Abstract Book

S520 ESTRO 2020

overall survival and disease free survival were 97.8% (95% Confidence Interval [95% CI]: 94.1 - 99.2%), and 93.4 % (95% CI: 89.2 - 96.0%) respectively. Conclusion Early breast cancer irradiation by Tomotherapy provides low early and medium-term toxicities with good aesthetic results and quality of life; however longer follow-up is required to better assess late outcomes. PO-0975 Retrospective evaluation of clinical outcome and dosimetric aspects in breast cancer reirradiations J.A. Gomez Ramos 1 , F. Castaño 1 , J. Acosta 1 , V. Hernandez 2 , C. Aparicio 1 , E. Gomez 1 , M. Arquez 1 , L. Torres 1 , P. Araguas 1 , Y. López 1 , M. Arguís 1 , D. Gómez 1 , N. Cabré 1 , E. Rodriguez 1 , M. Arenas 1 1 Hospital Universitari Sant Joan de Reus, Department of Radiation Oncology, Reus, Spain ; 2 Hospital Universitari Sant Joan de Reus, Physics Department, Reus, Spain Purpose or Objective Locally recurrent breast cancer (LRBC) to a previously irradiated area often generates doubts about the most suitable approach for the patient. The main objective of this retrospective study is to evaluate overall survival (OS)in patients undergoing external radiotherapy for LRBC. As secondary objectives we evaluated disease-free survival (DFS) and the degree of toxicity related to dosimetric aspects and to the time elapsed since the previous Between 2010 and 2018, 30 women (mean age = 66.3 years, range: 39-86 years) were re-irradiated with external radiotherapy for LRBC, with total irradiation of the breast/thoracic wall +/- regional lymph nodes +/- boost. The following variables were studied: type of primary cancer (histology, molecular classification, grade), type of recurrent cancer (histology, molecular classification, grade), site of recurrence, radiotherapy technique, total dose, total boost dose, fraction dose, equivalent dose in 2Gy fractions (EQD2), retreatment time, type of rescue surgery, OS, DFS as well as acute and chronic dermatitis were evaluated in the present study. All statistical calculations and graph representations were performed with the statistical package for social sciences (SPSS 22.0) and the OS and DFS analysis was performed using the Kaplan-Meier method. Results Radiation therapy was administered to the breast/thoracic wall +/- regional lymph nodes +/- boost in 30 re-irradiation treatments (level I-IV nodes in 6 cases). The mean cumulativeEQD2 for the entire breast and tumor cavity (α / β = 3) was 99.1 Gy and 117.9 Gy, respectively. The mean retreatment time was 93.5 months. OS and DFS at 5 years were 88% and 63.3%, respectively. Acute dermatitis was G1-2 in 22 cases, G3 in 2 cases and G4 in 0 case. Chronic toxicity was G1-G2 in 21 cases, G3 in 4 cases and G4 in 1 case (most commonly fibrosis and telangiectasia changes, 1 case of ulceration). Patients presentingthe highest grades of acute toxicity (G3) and chronic toxicity (G3 and G4) received an EQD2 of 112,5Gy and 110Gy, respectively, although the difference in EQD2 with respect to mild toxicity cases (G1 and G2)was not statistically significant. Events of acute toxicity (G3) and chronic toxicity (G3 and G4) had a mean retreatment of 10,5 and 9,5 years respectively, although the difference in EQD2 with respect to mild toxicitycases (G1 and G2)was againnot statistically significant. radiotherapy treatment. Material and Methods

Conclusion Reirradiation treatments exhibited very good results regarding OS, DFS and patient toxicity, which validates our current reirradiation protocol. There were no significant differences when comparing severe vs mild toxicity with respect to EQD2 and the retreatment time interval. PO-0976 Left sided breast cancer patients and advanced radiotherapy techniques. A cardiac sparing approach. F. Cucciarelli 1 , M. Parisotto 2 , S. Costantini 1 , C. Di Carlo 1 , F. Fenu 1 , S. Di Biase 1 , L. Vicenzi 1 , M. Di Benedetto 1 , A. Maucieri 1 , M. Montisci 1 , V.E. Morabito 2 , M. Valenti 2 , S. Maggi 2 , G. Mantello 1 1 Azienda Ospedaliero Universitaria Ospedali Riuniti, Radiotherapy Department, Ancona, Italy ; 2 Azienda Ospedaliero Universitaria Ospedali Riuniti, Medical Physics, Ancona, Italy Purpose or Objective To improve target coverage and reduce dose to heart and left anterior descending artery (LAD) in left breast cancer patients (pts) with comorbidities and unfavorable anatomy using volumetric modulated arc therapy (VMAT) with or without deep inspiration breath hold (DIBH). Material and Methods Between July 2015 and May 2019, 61 consecutive pts affected by left breast cancer with comorbidities and unfavorable anatomy underwent radiotherapy (RT) with