Abstract PS7-77: Pathological response after neoadjuvant chemotherapy and long-term outcomes among very young women with HER2 negative breast cancer

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Abstract Purpose: To describe the pathological response rates (according to the MD Anderson RCB score) achieved by patients with 35 years old or younger, with HER2 negative breast cancer, who received neoadjuvant chemotherapy (NAC) and long term outcomes according to the response. Methods: A retrospective review of 526 medical records of women aged less than or equal to 35 years at diagnosis between 2009 and 2014 at INEN in Lima-Peru, who received NAC for invasive breast cancer, was performed. HER2 positive patients were excluded because of a lack of access to neoadjuvant anti-HER2 therapy during this period in our hospital. Descriptive statistics were used to describe baseline characteristics. OS was calculated from the date of diagnosis to death or last follow-up and presented as Kaplan-Meier curves. The comparison among patients who achieved pCR (RCB-0) and those with residual disease, was based on a log-rank test. Results: Seventy women (One with synchronous bilateral disease) were selected according to selection criteria, median age: 31.7 years old (IQR: 30.0-33.2). Hormone receptor-positive: 38 (53.5%). Clinical stage: IIA: 13(18.3%), IIB: 8(11.3%), IIIA: 25(35.2%), IIIB: 21 (29.6%) and IIIC: 4 (5.6%). Type of NAC: Anthracyclines 6 (8.6%), Anthracyclines and taxanes 55 (78.6%), Platin 5 (7.1%), Taxanes 4 (5.7%). Type of surgery: Conservative 16 (22.5%), radical 50 (70.4%), toilet 5 (7.0%). Type of pathological response RCB-0: 9(12.7%), RCB-I: 2(2.8%), RCB-II:29(40.8%), RCB-III: 24(33.8%), non-pCR: 7(9.9%). With a median follow-up of 46.5m, 5y OS: 100/100/79.3/45.8% according to RCB-0/I/II/III respectively (p=0.004). Conclusions: "Very young" women reach fewer pCR rates than reported for "young" and older women. Even so, RCB-0 can be considered as a biomarker of excellent prognosis and could be used as a surrogate biomarker to evaluate the efficacy of neoadjuvant therapy even in very young women who receive NAC. Citation Format: Fernando Valencia, Jorge Laboriano, Luis A. Chirinos, Henry L. Gomez. Pathological response after neoadjuvant chemotherapy and long-term outcomes among very young women with HER2 negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-77.