Metastatic Behavior of Breast Cancer Subtypes

Patients with early-stage breast cancer diagnosed between 1986 and 1992 with archival tissue were included. Subtypes were defined as luminal A, luminal B, luminal/human epidermal growth factor receptor 2 (HER2), HER2 enriched, basal-like, and triple negative (TN) nonbasal. Distant sites were classified as brain, liver, lung, bone, distant nodal, pleural/peritoneal, and other. Cumulative incidence curves were estimated for each site according to competing risks methods. Association between the site of relapse and subtype was assessed in multivariate models using logistic regression.

Median follow-up time among 3,726 eligible patients was 14.8 years. Median durations of survival with distant metastasis were 2.2 (luminal A), 1.6 (luminal B), 1.3 (luminal/HER2), 0.7 (HER2 enriched), and 0.5 years (basal-like; P