ER-Positive Breast Cancer Remains a Long-Term Concern

The optimal duration of adjuvant endocrine therapy for early-stage, estrogen receptor–positive (ER+) breast cancer — long believed to be 5 years — is still an open question, as this treatment must be individualized. Clinical trials have explored endocrine therapy for up to 10 years. These extra years of treatment, despite their added value, represent a small incremental improvement in outcome that is often limited to a reduction in contralateral breast cancer rather than distant metastatic disease. Understanding which patients are at greatest risk for recurrence and whether they benefit from extended therapy remain key challenges. Researchers for the Early Breast Cancer Trialists' Group conducted a meta-analysis of 88 clinical trials involving 62,923 women with ER+ early-stage breast cancer who remained disease-free after 5 years of adjuvant endocrine therapy. They analyzed tumor (T) size, nodal (N) status, and grade in relation to outcomes after 5 to 20 years of follow-up.

For any initial tumor size or nodal burden category, cumulative risk for distant recurrence rose with follow-up time throughout the study period. Similarly, for any tumor grade category — even in Stage I (T1N0) disease — cumulative risk escalated over time. Nonetheless, the degree of risk (range, 10%–40%) was markedly correlated with initial TN status.