Is HER2-Low Breast Cancer a Distinct Prognostic Entity? Real-World Survival Outcomes from a Cohort in Colombia

Background/Objectives: The HER2-low classification has redefined therapeutic strategies, but its prognostic significance remains uncertain. We compared overall survival (OS) and progression-free survival (PFS) across HER2 categories (HER2-low, HER2-negative, HER2-positive) in a real-world cohort.

Methods

This was a single-center retrospective cohort study conducted at a high-complexity cancer center in Colombia; it included 373 patients with invasive breast cancer classified as HER2-positive (IHC 3+ or ISH+), HER2-low (IHC 1+ or 2+/ISH−), or HER2-negative (IHC 0). Survival was estimated by Kaplan–Meier. Multivariable Cox models were adjusted for age, clinical stage, histological grade, and hormone receptor status, and PFS was additionally analyzed separately in stage I–III and stage IV disease.