ESTRO 2021 Abstract Book

S917

ESTRO 2021

During the follow-up period, no patient had an EF alteration. Mean variation of LV GLS was -1.8% [-7.7; +5.5], -2.5% [-18.3; +6.1] and -2.1% [-16.1; +6.3] at 3, 6 and 12 months respectively. At 3 months, no LV GLS was noted. Five patients (9.2%) had significant LV GLS alteration at 6 months. Among these patients, 4 had a significant improvement in LV SLG at 12 months. No more alterations were noticed at 12 months. There was no significant difference in mean Dmean of WH or WLV between patients with and without LV GLS alteration. AB, SB and AM segments showed significantly more alterations than the other segments at 3, 6 and 12 months. Mean Dmean in altered segments was significantly higher the non-altered segments 7.3Gy vs 9.7Gy (p=0.01). Conclusion The results of our study show that STE is more effective than TTE for detecting sub-clinical cardiac alteration after left sided breast cancer RT. In addition, since there was no significant alteration at 3 months, we suggest, to make the control only at 6 months from the end of the RT to avoid unnecessary checks. At 12 months we can control only patients with LV GLS alteration at 6 months. Moreover, while planning RT, the WH and WLV delineation seems to be insufficient and the segmental delineation of the LV is necessary. We suggest not to exceed Dmean of 7 Gy at the segmental level to limit segmental alterations of the heart. PO-1102 Intraoperative Radiotherapy In Breast Cancer In Early Stages: Local Control And Toxicity. C. Escuin 1 , M. Cerrolaza 1 , V. Navarro 1 , A. Lanuza 1 , A. Campos 1 , S. Flamarique 1 , E. Hernando 2 , V. Rodrigo 3 , C. Casamayor 3 , A. Palomares 2 , F. Villalobos 4 , R. Ibañez 1 1 University Hospital Miguel Servet, Radiation oncology, Zaragoza, Spain; 2 University Hospital Miguel Servet, Surgery, Zaragoza, Spain; 3 University Hospital Miguel Servet, Surgery , Zaragoza, Spain; 4 University Hospital Miguel Servet, Gynecology, Zaragoza, Spain Purpose or Objective Partial breast irradiation can be offered to patients selected with early breast cancer as an effective and safe alternative to local treatment with radiotherapy. Local cancer control and the profile of toxic effects of intraoperative monotherapy radiotherapy in early-stage breast cancer are presented in our series. Materials and Methods We studied 604 patients who meet criteria for intraoperative radiotherapy as monotherapy (infiltrating ductal carcinoma smaller than 3 cm, unifocal, with clinically and radiologically negative axillary lymph nodes, positive hormone receptors and negative HER2) who are treated in Aragon (Spain) between May 2015 and December 2020. Intraoperative radiotherapy is performed with a single dose of 20 Gy administered with 50 Kv photons (Axxent equipment), on the surgical bed in the same act in the operating room. The results are analyzed in terms of disease control and local effect profile (skin toxicity, hematoma, seroma, infection and fibrosis). Results After surgery, 142 (23.5%) patients needed to complete treatment with external radiotherapy (whole breast radiotherapy) because they did not meet some of the criteria for intraoperative radiotherapy as monotherapy (positive lymph node in the selective sentinel node biopsy). Regarding toxicity, 1.1% of hematomas that required surgical drainage have been detected, 1.31% seroma requiring 2 or more evacuation punctures, 2 infections that required surgical drainage and 3.04% grade II fibrosis. With a median follow-up of 991 days, 5 local recurrences and 2 with distant involvement have been detected. This result is not greater than that obtained in the Targit-A trial. Conclusion Treatment with intraoperative radiotherapy as monotherapy in patients with early stage breast cancer is an effective and safe treatment in the analyzed sample. Further follow-up is necessary to confirm these results. PO-1103 Lung Cancer Mortality Among 316,336 Radiotherapy-Treated Early Stage Breast Cancer Cases S. Abera 1 , R. Mikolajczyk 2 , E. Kantelhardt 2,3 , L. Efremov 4,5 , A. Bedir 5 , C. Ostheimer 6 , A. Glowka 6 , D. Vordermark 6 , D. Medenwald 6,4 1 Faculty of Medicine, Martin-Luther-University Halle-Wittenberg, Department of Radiation Oncology, Halle Saale., Germany; 2 Interdisciplinary Center for Health Sciences, Medical School of the Martin-Luther- University Halle-Wittenberg, Institute for Medical Epidemiology, Biometrics and Informatics (IMEBI), Halle Saale., Germany; 3 Faculty of Medicine, Martin-Luther-University, Department of Gynaecology, Halle Saale., Germany; 4 Interdisciplinary Center for Health Sciences, Medical School of the Martin-Luther-University Halle- Wittenberg , Institute for Medical Epidemiology, Biometrics and Informatics (IMEBI), Halle Saale., Germany; 5 Faculty of Medicine, Martin-Luther-University Halle-Wittenberg , Department of Radiation Oncology , Halle Saale., Germany; 6 Faculty of Medicine, Martin-Luther-University Halle-Wittenberg, Department of Radiation Oncology , Halle Saale., Germany Purpose or Objective To estimate the risk of death from lung cancer in patients treated for breast cancer (BC) in relation to the general population. Materials and Methods BC data, covering 2000 to 2015, were extracted from the Surveillance, Epidemiology and End Results-18 (SEER- 18) cancer registry database. A comparison of lung cancer attributed mortality between BC patients and the general population was performed using standardized mortality ratios (SMRs) and SMRs conditional on survival length (cSMRs). Prognostic factors of lung cancer mortality were identified using flexible parametric modelling. Our model adjusts the effect of downstream (histopathological BC tumor grade and hormone receptor status) and upstream (age at diagnosis, ethnicity, and marital status) factors. Results