| Summary: | Abstract The human epidermal growth factor receptor-2 (HER2) enriched subtype of breast cancer is associated with early recurrence, mostly within 5 years. However, anti-HER2 therapies have improved outcomes and their benefits persist in the long term. This study aimed to determine predictive factors for late survival in patients with HER2-positive breast cancer. We analyzed 20,672 patients with HER2-positive stage I–III breast cancer. The patients were divided into two groups based on a follow-up period of 60 months. The multivariate analysis of factors associated with poor overall survival included old age, advanced pathologic tumor size stage (pT), advanced pathologic regional lymph node stage (pN), high histological grade, presence of lymphatic and vascular invasion, and HR-negative status within 60 months. In the breast cancer-specific survival (BCSS) of the > 60 months follow-up group, the hazard ratios (HRa) based on pN-negative were 3.038, 3.722, and 4.877 in pN1 (p = 0.001), pN2 (p < 0.001), and pN3 (p < 0.001), respectively. Only pT4 level was statistically significant in the pT group (HRa, 4.528; p = 0.007). Age (HRa, 1.045, p < 0.001) and hormone receptor-positive status (HRa, 1.705, p = 0.022) were also associated to worse BCSS. Although lymphatic invasion was not significantly associated with BCSS, there was a tendency toward a relationship (p = 0.079) with worse BCSS. In HER2-positive breast cancer patients, node status had a more significant relationship with long-term prognosis than T stage. Patients with HER2-positive breast cancer who have T4 or node-positive should be considered for clinical observation and education beyond 5 years.
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