Breast conservation among older patients with early-stage breast cancer: Locoregional recurrence following adjuvant radiation or hormonal therapy.

Background: For patients with breast cancer undergoing breast-conserving surgery (BCS), adjuvant radiation (RT) and hormonal therapy (HT) reduce the risk of locoregional recurrence (LRR). Although several studies have evaluated adjuvant HT ± RT, the outcomes of HT versus RT monotherapy remain less clear. In this study, the risk of LRR is characterized among older patients with early-stage breast cancer following adjuvant RT alone, HT alone, neither, or both.

Methods: This study included female patients from the Memorial Sloan Kettering Cancer Center (New York, New York) who were aged ≥65 years with estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) T1N0 breast cancer treated with BCS. The primary endpoint was time to LRR evaluated by Cox regression analysis.

Results: There were 888 women evaluated with a median age of 71 years (range, 65-100 years) and median follow-up of 4.9 years (range, 0.0-9.5 years). There were 27 LRR events (3.0%). Five-year LRR was 11% for those receiving no adjuvant treatment, 3% for HT alone, 4% for RT alone, and 1% for HT and RT. LRR rates were significantly different between the groups (P < .001). Compared with neither HT nor RT, HT or RT monotherapy each yielded similar LRR reductions: HT alone (HR, 0.27; 95% CI, 0.10-0.68; P = .006) and RT alone (HR, 0.32; 95% CI, 0.11-0.92; P = .034). Distant recurrence and breast cancer-specific survival rates did not significantly differ between groups.

Conclusions: LRR risk following BCS is low among women aged ≥65 years with T1N0, ER+/HER2- breast cancer. Adjuvant RT and HT monotherapy each similarly reduce this risk; the combination yields a marginal improvement. Further study is needed to elucidate whether appropriate patients may feasibly receive adjuvant RT monotherapy versus the current standards of HT monotherapy or combined RT/HT.