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.