Adjuvant chemotherapy in lobular carcinoma of the breast: a clinicopathological score identifies high-risk patient with survival benefit

Background Invasive lobular carcinomas (ILCs) represent approximately 10% of all breast cancers. Despite this high frequency, benefit of adjuvant chemotherapy (CT) is still unclear. Methods Our objective was to investigate the impact of CT on survival in ILC. Patients were retrospectively identified from a cohort of 23,319 patients who underwent primary surgery in 15 French centers between 1990 and 2014. Only ILC, hormone-positive, human epidermal growth factor 2 (HER2)-negative patients who received adjuvant endocrine therapy (ET) were included. End-points were disease-free survival (DFS) and overall survival (OS). A propensity score for receiving CT, aiming to compensate for baseline characteristics, was used. Results Of a total of 2318 patients with ILC, 1485 patients (64%) received ET alone and 823 (36%) received ET + CT. We observed a beneficial effect of addition of CT to ET on DFS and OS in multivariate Cox model (HR = 0.61, 95% confidence interval, CI [0.41–0.90]; p = 0.01 and 0.52, 95% CI [0.31–0.87]; p = 0.01, respectively). This effect was even more pronounced when propensity score matching was used. Regarding subgroup analysis, low-risk patients without CT did not have significant differences in DFS or OS compared to low-risk patients with CT. Conclusion ILC patients could derive significant DFS and OS benefits from CT, especially for high-risk patients.