Abstract P2-11-16: The safety and pathological impact of neoadjuvant radiotherapy for local advanced breast cancer undergoing mastectomy and autologous reconstruction

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Abstract Introduction Delayed breast reconstructions are preferred if post mastectomy radiotherapy is indicated due to lower complication rates compared to immediate permanent implant or autologous reconstructions (AR) but cosmetic outcomes are inferior. Radiotherapy has a deleterious effect on implants and autologous tissue and often an interim tissue expander is place which has inherent pain and complications. However, neoadjuvant radiotherapy (NART) prior to surgery allows for definitive oncological surgery to be performed with an immediate AR in a single operation and the avoidance of a temporary expander. The aim of this study is to assess the safety and downstaging impact of NART. Methods This is a prospective review of patients who underwent NART at GenesisCare Victoria, the Austin and the Alfred hospital. 59 LABC patients (median age 49.2 years) were divided into two groups; clinically staged and pathologically staged for reporting. There were 15 pathologically staged patients (pStage 2A-3C) and 43 clinically staged patients (cStage 2A-3B). All patients initially underwent NACT, followed by NART (median dose 50.4Gy in 28 fractions) to the breast, supraclavicular fossa and level 3 axilla with or without coverage of their Level 1 and 2 axilla, and/or internal mammary nodes. Approximately 6 weeks after completing NART, patients underwent definitive surgery and AR. Results All patients completed their NART with minimal toxicity and no break in treatment. 55 patients had a skin-sparing mastectomy (SSM) and 3 patients had a modified radical mastectomy. All clinically staged patients underwent an AD. ARs with a DIEP flap were performed in the majority of patients (51). The average length of hospitalisation was 6.2 days. The Miller Payne (MP) scoring index was used to record pathological responses in clinically staged patients. Overall 36 patients achieved significant downstaging of their disease, with MP scores of 5/5 for 20 and 4/5 for 16. Only 1 patient failed to achieve any downstaging with a MP score of 1/5. All 12 Her2 positive patients, 3/5 Triple negative patients and 5/26 Luminal A/B patients achieved a MP score of 5/5. All patients achieved R0 resection margins. This included 6 patients who had initial cT4 disease (cT4a X2, cT4b X1 and cT4d X3). 15 patients had initial cN2/3 disease and all successfully underwent their axillary dissections with R0 resections achieved. 10/15 had no involved axillary nodes with significant scarring seen in 6. 5/15 had residual involved nodes with significant scarring seen in 3 patients. Post surgical toxicities were graded using Clavien-Dindo classification. 8 significant grade 3 toxicities were seen in 6 patients, with no grade 4 or 5 toxicities. No patients developed DVT or PE. No flap losses were seen. Median follow up is 23 months. Cosmesis was rated as good to excellent in all cases. 1 patient developed simultaneous loco-regional and distant recurrence with another 3 patients developing distant metastases only. Conclusion This review demonstrated that NART is a safe technique, which has not lead to an increase in surgical complication rates or resulted in a detriment in cosmetic outcome. NART can achieve a shorter, simpler reconstructive journey for patients. Citation Format: Baker C, Chao MW, Jassal S, Neoh D, Bevington E, Hyett A, Grinsell D, Loh SW, Zantuck N, Stoney D, Foley C, Law M, Chew G, Yu V, Cheng M, Guerrieri M, Taylor K, Chipman M, Cokelek M, Lim Joon D, Foroudi F. The safety and pathological impact of neoadjuvant radiotherapy for local advanced breast cancer undergoing mastectomy and autologous reconstruction [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-16.

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