Abstract P2-14-16: Optimal timing to initiate adjuvant chemotherapy in Mexican women with high risk luminal breast cancer
Authors: Cabrera-Galeana Paula , Mendoza-Oliva Leticia , Muñoz Wendy , Villarreal-Garza Cynthia , Vázquez-Romo Rafael , Alvarado Alberto , Lara Fernando , Flores Diana , Matus Juan , Bargallo Enrique 
Published: March 2020

Abstract
Background: It is well known that the interval time (IT) to begin adjuvant chemotherapy (ADYCT) after surgical treatment, it is important to achieve better outcomes in breast cancer (BC), patients. After an IT of more than 91 days, the benefit of systemic treatment in breast cancer-specific overall survival (OS) decreases. Particularly in breast cancer patients with high proliferation tumors as a triple-negative subtype. There is a concern in low/middle-income countries as Mexico where early detection continues a challenge and the number of premenopausal women is high if this conventionally IT could be different in hormone-receptor-positive BC patients. Objective: Identify the optimal interval time between a curative surgical procedure and the adjuvant chemotherapy in high-risk luminal breast cancer patients to avoid a decrease in the overall survival benefit. Methods: We analyzed 749 patients with hormone-receptor-positive (HR+)/HER2 negative breast cancer that received ADYCT during 2006 and 2015 at the National Cancer Institute. HR-positive was defined using ASCO-CAP guidelines. ADYCT was based on anthracyclines and taxanes. Interval time was defined as the period in days between the date of surgical procedure and the date of the first dose of adjuvant chemotherapy. A ROC curve analysis was performed to identify the IT value that correlates with a decrease in OS. OS was calculated by the Kaplan-Meier method. We evaluated differences between survival curves with the log-rank test and used Cox’s proportional hazards model for the multivariate analysis. For statistical analysis, we used SPSS version 23.0. Results: The median follow up was 64.8 months. The median age was 52 years, 365 (48.7%) were premenopausal patients. The mean tumor size was 3 cm, 475 (63.4%) of patients had positive nodes, 80 (10.7%) had pN3, a high nuclear grade was reported in 327(43.7%) cases and 399 (53.3%) patients had Ki67 more than 20%. Mastectomy was performed in 565 (75.5%) and conservative surgery in 184 (24.6%) patients. Our cut-off value for IT was 42 days. Overall survival for patients with an IT less than 42 days was 115.2 months vs 108.8 months for those that initiated ADYCT in more than 43 days (p=0.002). In the univariate analysis for OS, we found significant stage IIB/III (p=0.003), IT more than 43 days (p=0.045), presence of positive nodes (p=0.001) and high nuclear grade (p=0.033). Finally, factors that influence negative OS in the multivariate analysis were positive nodes (HR 1.89, 95%CI 1.72-2.06; p&lt;0.001) and the IT more than 43 days (HR 1.57, 95%CI 1.38-1.77; p=0.049). Conclusions: It is important to recognize that IT time still matters in luminal breast cancer patients. So delays in ADYCT it's not recommended in a high-risk population with hormone-receptor-positive tumors. IT of 42 days seems to be the goal in our country to initiate ADYCT in the meantime early detection programs move forward.
Citation Format: Paula Cabrera-Galeana, Leticia Mendoza-Oliva, Wendy Muñoz, Cynthia Villarreal-Garza, Rafael Vázquez-Romo, Alberto Alvarado, Fernando Lara, Diana Flores, Juan Matus, Enrique Bargallo. Optimal timing to initiate adjuvant chemotherapy in Mexican women with high risk luminal breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-14-16.