Phase 2 partial breast irradiation (EBRT) trial tests localized radiation field to omit axillary staging

NYU Langone Health is running RADIANS (NCT07723209), a single-arm, prospective pilot evaluating the safety and longer-term regional control of partial breast irradiation (PBI) delivered with external beam radiation therapy after lumpectomy in women who intentionally omit sentinel lymph node biopsy or axillary dissection. The intervention is PBI—high-energy x‑ray EBRT focused on the lumpectomy bed/limited breast volume (a locoregional, not drug, mechanism) with dosing schedules allowed per treating radiation oncologist, plus required axillary ultrasound if not already done pre-op. The key scientific angle is whether a smaller radiation field can remain safe when surgical nodal staging is skipped, with the primary objective centered on axillary recurrence at 5 years and additional endpoints including local/distant recurrence and patient-reported outcomes (BCTOS-13 and financial toxicity). The eligible population is clinically node-negative, early-stage invasive ductal carcinoma treated with breast-conserving surgery without SLNB/ALND. Outside a trial, many similar patients receive lumpectomy followed by whole-breast irradiation (or selected PBI) plus endocrine therapy when hormone receptor–positive, with axillary staging often performed unless formally omitted by guideline-supported criteria.