National trends in dual de-escalation of axillary surgery and adjuvant radiation in early-stage HR+/HER2- breast cancer

Abstract Purpose De-escalation has become standard across breast cancer management. Many early-stage HR+/HER2-negative breast cancers are eligible for both SLNB omission and accelerated partial breast irradiation (APBI). However, the oncologic safety of dual de-escalation has not been evaluated except in patients ≥ 70 years. We sought to characterize national practice patterns and factors associated with adoption of this dual de-escalation approach. Methods Women aged 50–69 years with clinical T1–T2N0 breast cancer who underwent upfront breast-conserving surgery between (2012 − 2022) were identified from the National Cancer Database. Patients were categorized by axillary surgery and by adjuvant radiation modality (WBI, APBI, or none). We assessed trends and factors associated with de-escalation. Results 316,324 patients met inclusion criteria, of whom 98% underwent SLNB. Among patients who underwent SLNB, 83% received WBI, 11% received APBI, and 6% received no radiation. In contrast, among patients in whom SLNB was omitted, 63% received WBI, 8% received APBI, and 30% received no radiation. SLNB omission remained low throughout the study period at < 3%, while APBI use increased from 8% to 16.5%. Dual de-escalation was rarely performed throughout the study period remaining < 0.30%. Shared predictors of de-escalation included cT1 tumors, ductal histology, low grade, and treatment at academic/research programs. Conclusion These findings highlight the need for prospective studies to define the safety, outcomes, and patient selection criteria for combined de-escalation strategies. Until these data are available, patient-centered discussions are essential to determine the most appropriate strategy for patients with low-risk disease.