ER-positive breast cancer patients with more than three positive nodes or grade 3 tumors are at high risk of late recurrence after 5-year adjuvant endocrine therapy.

Purpose: Currently, although several clinical trials available give strong suggestions that extension of endocrine therapy has benefits, the risk level at which patients may benefit from extended endocrine therapy remains uncertain. This study aimed to identify the proportion of patients at a substantial risk of late recurrence after 5-year adjuvant endocrine therapy. Patients and methods: We reviewed 1,056 female patients with primary breast cancer who underwent curative resection between January 2006 and December 2011. Univariate and multivariate analyses were performed using the Cox proportional hazards regression model to identify prognostic factors. Results: A total of 327 eligible patients were eventually enrolled in this study. Among them, 42 (12.8%) patients suffered from distant metastasis and 34 (10.4%) patients experienced locoregional recurrence after 5-year adjuvant endocrine therapy. In multivariate analysis, patients with more than three positive nodes (hazard ratio [HR] = 2.176, 95% CI= 1.071-4.421; P= 0.032) and histologic grade 3 disease (HR= 2.098, 95% CI= 1.300-3.385; P= 0.002) were significantly associated with high risk of late recurrence. However, only histologic grade 3 (HR= 2.212, 95% CI= 1.166-4.194; P= 0.015) was significantly associated with high risk of distant metastasis. Conclusion: Late relapse after completion of 5-year adjuvant endocrine therapy was still common, and grade 3 and more than three positive nodes were the risk factors of late recurrence, while grade 3 was the only risk factor of late distant metastasis. These patients might benefit from extended endocrine therapy.