ESTRO 2020 Abstract book

S550 ESTRO 2020

progesterone receptor [PR] positive, human epithelial growth factor receptor-2 [HER2] negative), HER2 (HER2 positive), and triple negative (TNBC; HER2, ER and PR negative). Multivariate analyses for disease-free survival (DFS) and overall survival (OS) were also performed adjusting for unbalanced variables: pathologic complete response (pCR), histologic type and grade tumor. Results A total of 653 women were included. Most (589;91.1%) of the patients had locally advanced disease (clinical stage IIB to IIIC). Patients were distributed as following (N;%): luminal (300;45.9%), HER2 (173; 26.5%), TNBC (180;27.6%). The groups differ regarding pathologic complete response rate (pCR), histologic type and grade, where pCR were more frequent in HER2 (64;37.0%) and TNBC (52;28.9%) vs. Luminal (18;6%). The median follow-up time for surviving patients was 33 months. The disease-free survival (DFS) and overall survival (OS) rates for all patients at 3 years were 71% and 86%, respectively. The DFS and OS rates for all patients at 3 years were 71% and 86%, respectively. Patients with TNBC had worse DFS and OS rates at 3 years: (3year-DFS: 72%, 76%, and 64%; 3year-OS: 88%, 88% and 78%, for Luminal, HER2 and TNBC, respectively). Comparing to TNBC, Luminal had better DFS (HR 0.67; 95%CI 0.46-0.97) and OS (HR 0.54; 95%CI 0.32-0.90), in multivariate analysis, while no statically difference was seen between HER2 vs. TNBC (DFS HR 0.73; 95%CI 0.49- 1.10; OS HR 0.63; 95%CI 0.36-1.09). Conclusion In locally advanced breast cancer patients who underwent NAC, survival rates were different based on the molecular subtype, with TNBC having the poorest prognosis. PO-0945 The impact of surgery type in breast cancer patients that received neoadjuvant chemotherapy G. Marta 1 , A. Pereira 2 , J. Oliveira 3 , F. José Roberto 4 , M. Max 3 1 Hospital Sirio Libanes, Radiation Oncology, Sao Paulo, Brazil ; 2 Hospital Sírio-Libanês, Department of Clinical Oncology, Brasilia, Brazil ; 3 Hospital Sírio-Libanês, Department of Clinical Oncology, Sao Paulo, Brazil ; 4 Instituto do Câncer do Estado de São Paulo ICESP - Faculdade de Medicina da Universidade de São Paulo FMUSP, Department of Obstetrics and Gynecology - Division of Breast Surgery, Sao Paulo, Brazil Purpose or Objective The aim of this study was to determine whether there were differences in survival outcomes of matched breast cancer patients undergoing breast-conserving surgery (BCS) versus mastectomy that received neoadjuvant chemotherapy (NAC). Material and Methods A retrospective cohort of patients with stage I-III breast cancer treated between 2008 and 2014 at two institutions who had received NAC followed by surgery and post- operative radiation therapy was identified. Kaplan-Meier and multivariate Cox proportional hazards models were used to examine disease-free survival (DFS) and overall survival (OS) rates by surgery type. Results Of 652 patients, 162 (24.9%) underwent BCS and 490 (75.1%) underwent mastectomy /adenomastectomy. Most of the patients (n=589, 91.1%) had locally advanced disease (clinical stage IIB to IIIC) with a mean age of 50 years. In regards of surgery type, patients with stage III disease underwent more mastectomy them BCS (n=383, 79.0% mastectomy versus n=81,50.3% BCS; p<0.001). The DFS and OS rates for all patients at 3 years were 81.5% and 67.5% (p=0.001); 88.9% and 83.9% (p=0.174) for BCS and mastectomy groups, respectively. Despite these differences, in the multivariate analyzed adjusted by clinical stage and pathologic complete response, there were no statistical differences in DFS (mastectomy versus BCS HR 1.44; 95% CI 0.95 - 2.17) and OS (mastectomy

TE, 3 (5.66%) were capsular contractures, Baker grade 1- 2, one(1.88%) minor skin infection and one(1.88%) skin dehiscence, without implant exposure. Among IBR, we observed 3(6.12%) grade 1-2 capsular contracture. With regards to major complication, we observed one case (1.8%) of major wound dehiscence with implant exposure and 6 (11.32%) capsular contracture Baker grade 3-4 among TE patients. In the IBR group, there were 7 (14.28%) capsular contracture Baker grade 3-4 and one (2.04%) severe infection. These were classified as major complications requiring implant or prosthesis removal. Conclusion we did not observe any significant difference in minor and major complication rate according to the type of reconstruction. Hypofractionated PMRT confirmed its safety. PO-0943 Long-term results of hypofractionation with simultaneous integrated boost in early breast cancer. K.S. Athigakunagorn 1 , C. Nantavithya 2 , K. Shotelersuk 1 , P. Rojpornpradit 2 1 Chulalongkorn University, Division of Therapeutic Radiology and Oncology- Faculty of Medicine, Bangkok, Thailand ; 2 King Chulalongkorn Memorial Hospital- Thai Red Cross Society, Division of Therapeutic Radiology and Oncology- Department of Radiology, Bangkok, Thailand Purpose or Objective To report long-term results of hypofractionated whole breast irradiation with simultaneous integrated boost (SIB) Between October 2009 and June 2010, 73 patients with early breast cancer (T1-3N0-1M0) who underwent breast conserving surgery were accrued in the study. Thirty-six of these patients received conventional irradiation as 50 Gy in 25 fractions to the whole breast with a sequential boost to the tumor bed of 10–16 Gy in 5–8 fractions over 5 weeks (conventional group), while the other 37 patients received a hypofractionated dose of 43.2 Gy in 16 fractions with an additional daily boost of 0.7 Gy over 3 weeks (hypofraction At a median follow-up of 114 months, ipsilateral local recurrence (ILR) was found in three patients, two of which were in the hypofraction group. All of three ILR cases were found to be a true local recurrence. There was no significant difference in the 9-year disease free survival or 9-year overall survival rates between the conventional and hypofraction groups (91.7% vs . 83.3%, p = 0.319 and 94.4% vs. 91.9%, p = 0.664, respectively). Conclusion This study revealed that the effectiveness of hypofractionated whole breast irradiation with a SIB is comparable to conventional irradiation with a sequential boost in terms of disease free survival and overall survival. PO-0944 Molecular subtypes in patients with breast cancer that received neoadjuvant chemotherapy G. Marta 1 , M. Mano 2 , L. Oliveira 2 , A. Pereira 3 1 Hospital Sirio Libanes, Radiation Oncology, Sao Paulo, Brazil ; 2 Hospital Sírio-Libanês, Department of Clinical Oncology, Sao Paulo, Brazil ; 3 Hospital Sírio-Libanês, Department of Clinical Oncology, Brasilia, Brazil Purpose or Objective To evaluate the survival outcomes based on molecular subtypes of patients with breast cancer that received neoadjuvant chemotherapy (NAC). Material and Methods We performed a retrospective analysis of all non- metastatic breast cancer patients treated between 2008 and 2014 at two institutions who had received NAC followed by surgery and post-operative radiation therapy. Patients were divided into four groups based on the tumor molecular subtype: luminal (estrogen receptor [ER] / in early breast cancer. Material and Methods group). Results