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Abstract P5-16-10: Post-mastectomy radiotherapy following immediate implant based reconstruction: A possible solution to a reconstructive challenge

Aims: The National Mastectomy and Breast Reconstruction Audit report (NMBRA, 2011)1 revealed that immediate implant-based breast reconstruction (IIBR) was the most common type of primary reconstruction performed in the UK (37%). The main reason given by clinicians for not offering immediate breast reconstruction was the need for adjuvant radiotherapy. Post-mastectomy radiotherapy (PMRT) decreases the rate of local recurrence as well as increase the long-term survival in patients who demonstrate intermediate to high-risk features2,3 but has been shown to increase the risk of implant complications in IIBR by up to 24% (Berry et al, 2010)4. Cordeiro et al (2004)5 showed the incidence of capsular contracture was 28% higher in the PMRT group compared with non-irradiated patients. Most patients in the UK receive hypofractionated PMRT of 40.05Gy in 15 fractions over 3 weeks based on the UK Standardisation of Breast Radiotherapy (START) trial6, which demonstrated that hypofractionated PMRT is as safe and effective as the conventional PMRT of 50Gy in 25 fractions over 5 weeks. The aim of this study was to determine whether the conventional PMRT of 50Gy in 25 fractions over 5 weeks (2Gy per fraction) was associated with a reduced risk of implant complications in patients undergoing mastectomy with IIBR compared with hypofractionated PMRT regiment of 40.05Gy in 15 fractions over 3 weeks (2.67Gy per fraction). Methods: A single centre retrospective review of data on patients who underwent IIBR followed by PMRT between September 2012 and May 2017 was conducted. Radiotherapy-related complications (surgical site infection, contracture, implant rupture or leakage, wound breakdown) were compared between the two groups of patients receiving conventional and hypofractionated PMRT. Results: Fifty-nine patients underwent IIBR followed by PMRT. Twenty-six patients received hypofractionated PMRT and thirty-three patients received conventional PMRT. Radiotherapy-related complications occurred in 62% of patients in the hypofractionated PMRT group compared with 45% in the conventional PMRT group (p = 0.30). The incidence of capsular contracture (31% in vs. 21%, p = 0.55) and wound breakdown (23% vs. 15%, p = 0.51) was higher in the hypofractionated PMRT group, but surgical site infection (SSI) was more common in the conventional group (4% vs. 6%, p = 1.00). Discussion: Possible confounding factors (BMI, smoking status, and adjuvant chemotherapy) were not analysed due to the small sample size and limitations of the retrospective nature of this study. However, our overall rate of SSI is low in comparison with national data from the NMBRA (2011), which states the SSI rate of 25% in patients who underwent breast reconstruction surgery. Conclusions: This study suggests that the rate of radiotherapy-related complications is lower in patients treated with conventional PMRT compared with hypofractionated PMRT, however the sample size is too small to demonstrate statistical significance. Further research is required to evaluate the effectiveness of conventional PMRT as an option to facilitate immediate implant-based reconstruction following mastectomy. Citation Format: Chaichanavichkij P, Arun KS, Conibear J, Ullah MZ. Post-mastectomy radiotherapy following immediate implant based reconstruction: A possible solution to a reconstructive challenge [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-16-10.