ESTRO 2023 - Abstract Book

S103

Saturday 13 May

ESTRO 2023

Conclusion The MV health status predicts acute toxicity in BC pts: in our study population, an impaired MV was associated with higher susceptibility to RT. The role of DNA damage repair mechanisms in microcirculation diseases was already known in the literature. These data suggest an interaction of compromised MV with repair mechanisms needed to repair RT damage. This kind of systemic functional information derived by a sublingual microscope could be exploited in different cancer districts, boosting the personalisation of predictive models and their tailoring to the single patient functional status. This study was funded by AIRC Investigator Grant, no. IG21479. MO-0141 The Impact of 2019 ESTRO-ACROP target volume delineation guideline on breast-related complications J.B. Park 1 , B. Jang 1 , J.H. Chang 1 , J.H. Kim 1 , K.Y. Hong 2 , U.S. Jin 2 , H. Chang 2 , Y. Myung 3 , J.H. Jeong 3 , C.Y. Heo 3 , I.A. Kim 4 , K.H. Shin 1 1 Seoul National University Hospital, Radiation Oncology, Seoul, Korea Republic of; 2 Seoul National University Hospital, Plastic and Reconstructive Surgery, Seoul, Korea Republic of; 3 Seoul National University Bundang Hospital, Plastic and Reconstructive Surgery, Seongnam, Korea Republic of; 4 Seoul National University Bundang Hospital, Radiation Oncology, Seongnam, Korea Republic of Purpose or Objective The European Society for Radiotherapy and Oncology Advisory Committee in Radiation Oncology Practice (ESTRO-ACROP) recently updated a new target volume delineation guideline for postmastectomy radiotherapy (PMRT) after implant-based reconstruction. This study aimed whether this change has impact on breast-related complications. Materials and Methods We retrospectively reviewed patients who underwent PMRT after mastectomy with tissue expander or permanent implant insertion from 2016 to 2021. In total, 400 patients were included; 264 received RT by the new ESTRO-ACROP target delineation (ESTRO-T), and 136 received RT by conventional target delineation (CONV-T). The primary endpoint was comparison between the target groups of major breast-related complication, including infection, capsular contracture, deformity and necrosis requiring re-operation or re-hospitalization during follow-up after RT or delayed implant replacement. Complications were evaluated according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0., and capsular contracture was graded by the Baker Classification. Results The median follow-up was 29.5 months (range, 0.3-76.8). The 1-, 2-, and 3-year incidence rates of major breast-related complication were 5.4%, 9.4%, and 12.0% in the ESTRO-T group, and 8.2%, 13.9%, and 14.8% in the CONV-T groups; it did not show a difference between the groups (P = 0.52, Figure 1.(A)). In multivariate analyses, target delineation is not significantly associated with the major complications (hazard ratio [HR] = 0.93; P = 0.83). There was no significant difference between the ESTRO-T and CONV-T groups in the incidence of any breast-related complications (3-year cumulative incidence, 36.0% vs. 30.1%, respectively; P = 0.29, Figure 1.(B)). Symptomatic RT-induced pneumonitis rates were 2.7% in the ESTRO-T group (7 patients) and 2.2% in the CONV-T group (3 patients). Only one local recurrence event occurred in the ESTRO-T group, which was within the ESTRO-target volume. Figure 1.