Prognostic difference between early breast cancer patients with HER2 low and HER2 zero status

We aimed to investigate the differences in prognosis between patients with HER2-low and HER2-zero status. This retrospective cohort study conducted at multi-institution included 1627 patients diagnosed with HER2-low or HER2-zero breast cancer (stages I-III). Survival analysis after propensity score matching was used. In total, 445 patients with HER2-low and 707 patients with HER2-zero status were included. The median follow-up was 92.7 months. Locoregional and distant recurrence-free survival were comparable between patients with HER2-low and HER2-zero status (p = 0.872, p = 0.746, respectively). HER2-low status did not affect overall survival. However, in subgroups with lymph node metastases, patients with HER2-low status showed better recurrence-free survival compared with that of patients with HER2-zero status (p = 0.033). In conclusion, survival outcomes were comparable between patients with HER2-low and HER2-zero breast cancer. More studies are needed to validate our findings and examine the biological mechanism underlying these prognostic differences.