Introduction: Invasive Lobular Breast Cancer (ILC) harbors unique clinicopathologic features. Data on optimal treatment modalities focusing on ILC remain scarce. We aim to investigate the benefit of chemotherapy in early-stage hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2-) ILC.
Methods: Female patients with early HR+/HER2- ILC (stages I-III) who underwent surgery were selected from the National Cancer Database (2010-2016) and grouped into four treatment cohorts: surgery only(S), chemotherapy alone (CT), endocrine therapy alone (ET), and combined chemotherapy followed by endocrine therapy (CET). Descriptive and bi-variate statistics summarized baseline characteristics and compared them across cohorts. A secondary analysis accounting for OncotypeDX (ODX) information was performed, stratifying for low (<26) and high (≥26) ODX. Kaplan-Meier (KM) and Cox proportional hazard models evaluated the relationship between treatment modality and overall survival (OS), stratifying for ODX scoring.
Results: N = 15,271 patients were included. The CET cohort (29.8%) was more likely to be younger and have no co-morbidities, advanced tumor stage or high ODX score (≥26). No significant difference in OS comparing ET to CET (HR:1.08, 95%CI:0.93-1.26, p = 0.31) was observed, adjusting for confounders. N = 5,561 patients had ODX results available. No significant difference in 5-year OS was observed comparing the ET to CET cohorts, both in patients an ODX score <26 (HR:1.10; 95%CI:0.69-1.76, p = 0.69) and ODX score ≥26 (HR:1.18; 95%CI:0.51-2.75, p = 0.69).
Conclusion: Chemotherapy demonstrated no added survival benefit in HR+/HER2- ILC, even in tumors with ODX ≥26. Prospective trials identifying potential subgroups of patients with ILC who could benefit from chemotherapy are needed.
Keywords: Breast Neoplasms, pathology; Breast neoplasms, drug therapy; Breast neoplasms, genetics; Genomics, methods.
Copyright © 2022. Published by Elsevier Ltd.