74 Surgical-Decision Making Following Neoadjuvant Chemotherapy in Primary Breast Cancer: A Single-Centre Study

Abstract Background The use of Neoadjuvant Chemotherapy (NACT) for managing early breast cancer is increasing. While recent studies indicate the potential for tumour downsizing, this may not necessarily result in surgical de-escalation in the breast or axilla. This study aimed to determine a single UK unit's rate of surgical de-escalation following NACT. Methods This retrospective service evaluation from a single UK unit (registered audit 23-912) reviewed patients with primary breast cancer treated with NACT between January 2020 and December 2024. The electronic records of patients were reviewed and the data was extracted. Results 77 patients (mean age of 45.8 ± 11.1) exhibited the following tumour phenotypes: 27% HER2+ve, 34% HER2+ve ER/PR+ve, 9% HER2- ER/PR+ve and 32% Triple Negative. The initial surgical plans recorded before treatment included: Breast Conserving - 42%, Mastectomy - 32% and Not clear - 26%. A clear de-escalation of operation from mastectomy to breast conservation occurred in 20% of patients eligible for NACT. Moreover, 80% of patients with an unclear initial surgical plan underwent breast conservation. At the axilla, 42% of biopsies were confirmed as node-positive at diagnosis, with 39% undergoing axillary node clearances (ANC). Interestingly, 53% of the patients who underwent ANC had no evidence of residual disease on post-operative histology. Conclusion The unit likely has surgical de-escalation rates similar to recent national findings but there is likely scope to increase this given pathological complete response rates of 70-80%. This evaluation has promoted changes in documentation and the timings of MDT discussions to optimise decision-making.