ESTRO 38 Abstract book

S723 ESTRO 38

tissue toxicity were assessed respectively, at the end of RT and one year after treatment. The Radiation treatment tolerance was assessed using the acute and late radiation morbidity scoring criteria from the Radiation Therapy Oncology Group (RTOG) scale. Aesthetic result was evaluated according to the Harvard scale. Results In groupA SIB was added in 22 pts(45%). In groupB a concomitant boost of 3 Gy was added in 31pts and a boost of 4Gy in the remaining 17pts. G3-G4 acute skin toxicity was not observed in both groups; G2 acute side-effects were significantly low: at the end of the treatment only 4 women in groupA and just one in groupB needed topic steroid therapy for G2 dermatitis, which ameliorated within 3 weeks after irradiation. 17 pts (groupA) and 24pts (groupB) showed G1 erythema. Concerning late subcutaneous tissue toxicity (12 months), fibrosis occurred in groupA as follow: G2 2 pts, G1 5pts, G0 41pts; furthermore 1 patient developed hyperpigmentation. As regard group B fibrosis G2 2 pts, G1 8 pts and G0 38pts, 2 patient showed a slight skin retraction. Aesthetic outcomes were from good to excellent in 94% and from fair to poor in 6% in groupA, and respectively 96% and 4% in groupB.

Purpose or Objective Previous studies showed that second primary lung cancer (SPLC) is likely increased with the occurrence of ionizing radiation (RT) on BC patients (pts.). However, RT is not often used alone and SPLC is a rare event, therefore the risk of RT might be overestimated. To test the hypothesis that SPLC is associated with RT, we conduct this national population based, propensity score-matched (PSM) follow up study. Material and Methods We reviewed all Taiwanese female, 20-80 years-old BC pts. in the databases of Taiwanese National Health Insurance and Taiwan Cancer Registry between 01 January 2002 to 31 December 2010. Exclusion criteria are: (1) missing or invalid demographic information; (2) had another cancer diagnosis before and six months post BC diagnosis date (index date, ID). To analysis the risk of RT alone, we excluded pts. (3) had received Cobalt 60 and other RT except linear accelerated RT; (4) had been treated with CT or died within a year after ID. To exclude patients who had uncompleted RT, we did not recruit pts. (5) had more than 1 fraction and less than 49 fractions of RT within one year after ID. We used PMS (1:2) to match pts. with RT (RT group) with those had no RT (non-RT group) to compare the incidence of SPLC later in both groups. The propensity scores for RT were formulated using 6 covariates: age, diagnostic year, social economic status (SES), residence, Charlson Comorbidity Index (CCI), and comorbidities. Standardize mean difference (SMD) and p-value (CI 95%) were used to compare the baseline characteristics of groups. End of follow up time is 31 December 2015 and subdistribution hazard ratio (sHR) was used in competing-risk regression models. Results From 64758 BC recorded in the databases, 48996 pts. were excluded based on mentioned exclusion criteria. Among these 15762 eligible Taiwanese female primary BC pts., 4614 pts. had RT and 11148 pts. without RT. After matching, the differences between two group (age, diagnostic year, CCI and certain concurrent diseases) were reduced and the similarities were increased significantly. We revealed 29 SPLC in RT group (3539 pts., 29657 person- year follow up) and 57 SPLC in non-RT group (7078 pts., 56914 person-year follow up). Adjusted sHR was performed based on competing risk model adjusted for PMS covariates and we observed no difference between the two groups (p=0.949). BC pts. who have lumpectomy are likely to have less radiation exposure to the lung than those have mastectomy. We divided RT group into two subgroups based on type of their surgery. Significant covariate differences were also observed at baseline. After matching, there were no statistical differences in the SPLC incidences between two groups (p=0.247). Conclusion Our current results showed RT in the absence of CT does not increase the development of SPLC on Taiwanese female BC patients. We need further studies to identify specific agents using concurrent with RT is able to increase the risk of SPLC. EP-1320 Estimated survival benefit and cardiovascular risk due to radiotherapy for breast cancer in Chile T. IP 1 , G. Martínez 2 , C. Sánchez 3 , R. Fernández 2 , L. Bravo 4 , M. Pinto 4 , E. Vinés 1 , T. Merino 1 1 Pontifica Universidad Católica de Chile, Radiation Oncology, Santiago, Chile ; 2 Pontifica Universidad Católica de Chile, Cardiology, Santiago, Chile ; 3 Pontifica Universidad Católica de Chile, Medical Oncology, Santiago, Chile ; 4 Pontifica Universidad Católica de Chile, Oncology, Santiago, Chile

Conclusion Once weekly hypofractionated radiation therapy resulted comparable to ten fractions regimen without evidence of inferior treatment feasibility or higher adverse effects. Once weekly radiation therapy can be recommended as a safe and effective alternative for whole-breast adjuvant radiotherapy in elderly pts. EP-1319 Second primary lung cancer unlikely associated with irradiated breast cancer population in Taiwan T.T. Ngo 1 , L. Chien 2 , L. Chen 3 , L. Lu 4 1 Taipei Medical University, International PhD/Master Program in Medicine- College of Medicine, Taipei, Taiwan ; 2 Taipei Medical University, School of Health Care Administration- College of Management, Taipei, Taiwan ; 3 Taipei Medical University, Health and Clinical Data Research Center- College of Public Health, Taipei, Taiwan ; 4 Taipei Medical University, Graduate Institute of Biomedical Materials and Tissue Engineering- College of Biomedical Engineering, Taipei, Taiwan