Abstract P2-10-03: Real world outcomes of adjuvant chemotherapy in invasive lobular carcinoma of the breast: a retrospective cohort from a reference center in Brazil

Abstract Background: Invasive lobular carcinoma is the second most common breast cancer histology and has lower response rate to chemotherapy (CT) compared to ductal/no special type (NST) tumors. In the adjuvant setting, many guidelines recommend CT based on the criteria used for NST. However, the benefit of CT is not necessarily the same. Here, we present survival outcomes of patients with invasive lobular carcinoma from a retrospective cohort. Methods: This study has included patients seen at Instituto do Cancer do Estado de São Paulo, Brazil, between 2015 and 2020. Only patients with invasive lobular carcinoma in stages I-III have been enrolled. Results: After screening, 153 records from patients were included to review, divided in stages I (22%), II (47%) , and III (31%). Mean of age at diagnosis was 62y (range: 28 - 91 years). Received chemotherapy as adjuvant, neoadjuvant and omitted in 76 (50%), 16 (10%), and 61 (40%) respectively. The median of disease-free survival in adjuvant, neoadjuvant and omitted were respectively 11y, 1.4y and 9.4y (p=0.0001); and median of overall survival (mOS) were 13.3y, 5.5y and 7.5y (p = 0.0395). Analyzed by staging, for stage I mOS was not raged among groups (p=0.011), stage II 13y, 5.5y and 7.2y (p=0.006), and stage III: 6.2y, 5.9y, and 4.6y (p=0.56). In a multivariable Cox proportional regression, the hazard ratio (HR) for age, staging and HER2 3+ were 1.07 (p=0.001), 4.2 (p= 0.0001), and 8.9 (p=0.001) respectively. Conclusion: In our study, disease-free survival and overall survival were longer for adjuvant chemotherapy than neoadjuvant, specially for stage I and II. Although age, staging and HER2 3+ were independent risk factors for shorter overall survival. Citation Format: Raelson Miranda, Thamires Haick Martins da Silveira, Douglas Tozzo, Leticia de Mello Graziano, Laura Testa. Real world outcomes of adjuvant chemotherapy in invasive lobular carcinoma of the breast: a retrospective cohort from a reference center in Brazil [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P2-10-03.