ESTRO 2020 Abstract Book

S504 ESTRO 2020

5 Institut Curie, Department of Radiation Oncology, Paris, France Purpose or Objective In patients undergoing implant-based reconstruction, PMRT could increase rates of infections, capsular contracture, implant loss, and overall reconstructive failure requiring revisional surgery. The association between PMRT and poor reconstructive outcomes is well documented. Immediate prosthetic breast reconstruction produces a satisfactory aesthetic result, with high levels of patient satisfaction. However, many patients are advised against immediate breast reconstruction because of concerns of implant loss and infection, particularly those requiring chemotherapy. Our study aimed to evaluate the patient's outcome according to two radiotherapy PMRT regimens, standard vs. hypofractionation, and two different types of reconstruction: tissue expander (TE) vs. immediate breast reconstruction(IBR). Material and Methods This study was conducted on 102 pts treated at 1 French and 1 Italian institute from April 2012 to June 2016. PMRT was delivered in two different regimes. The prescription dose to the PTV was 50 Gy/25 fr. 5 times per week and 46 Gy/20 fr., 4 times per week. Two-stage expander-implant reconstruction was performed in 53 patients, and the exchange is within 6 months since PMRT; IBR was perfomed in 49 pts. Results Outcomes data were recorded retrospectively. We compared the complication rate after PMRT with either TE or IBR. Outcome measures included a) occurrence of capsular contraction, evaluated by using the four-grade Baker scale, b) reconstructive failure (implant loss), and C) aesthetic results. We recorded minor complications in 5 (9.26%) TE patients and 3 (6.12%) in IBR patients. Among 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 in early breast cancer. Material and Methods

a hypofractionated dose of 43.2 Gy in 16 fractions with an additional daily boost of 0.7 Gy over 3 weeks (hypofraction

group). Results

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] / 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,