Abstract PO4-22-09: Impact of time to surgery after neoadjuvant chemotherapy on pCR rate in locally-advanced breast cancer

Abstract Objective: Neoadjuvant chemotherapy along with surgical treatment are the important parts of treatment for locally advanced breast cancer. Extending the interval between the end of neoadjuvant chemotherapy and surgery may decrease tumor response in patients with locally advanced breast cancer. However, data if timing of surgery after neoadjuvant therapy affect the Pathologic complete response (pCR) rate is controversial. Materials and methods: We performed a retrospective analysis of 874 consecutive patients with IIIA-IIIC breast cancer that received neoadjuvant chemotherapy and surgery between 2000 and 2020 in N.N. Blokhin National Cancer Research Center. The median interval between the last injection of chemotherapy and surgery was 30 days (range 10 to 95 days). The variables were compared using log-rank statistics and Cox regression model. Results. Pathologic complete response (pCR) was registered in 250 (31,4%) patients. Univariate analysis showed that extending the interval between the end of neoadjuvant chemotherapy and surgery for each day were associated with decrease of probability of pCR (OR 0,982; p = 0,009). Patients with triple-negative and ER-/HER2+ achieved higher rates of pCR compared to luminal A subtype (p 0,0001). Tumor grade, tumor size, Ki67 were independent predictive factors for tumor pCR (p 0,001). Multivariate analysis also showed an independent negative effect of the time interval before surgery on the achieving pCR. Then the patients were stratified into three cohorts according to the time of surgery after neoadjuvant chemotherapy: 22 days, 22-42 days, or 42 days. The odds ratio (OR) for pCR was 1 for 22 days (reference), 0,833 for 22-42 days (p=0,332) and 0,576 for ≥43 days (p=0,033). Cox regression model demonstrated that the interval between the end of neoadjuvant chemotherapy and surgery (more than 42 days), tumor size, triple-negative and ER-/HER2+ were the significant predictive factors for pCR. Tumor grade, tumor size and age of patients were not independent predictive factors for in-breast pCR. Conclusion: Our study showed improved pCR if surgery was performed within 6 weeks after the end of neoadjuvant chemotherapy in locally advanced breast cancer. Results of multivariate logistic regression analysis to assess the probability of achieving complete pathomorphological regression Results of multivariate logistic regression analysis to assess the probability of achieving complete pathomorphological regression Citation Format: Alexander Petrovskiy, Viktory Amosova, Oxana Trofimova, Mona Frolova, Anastasya Soloshenko, Alexey Rumyantsev. Impact of time to surgery after neoadjuvant chemotherapy on pCR rate in locally-advanced breast cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-22-09.