Rewriting the radiation playbook: NSABP B-51 and the rise of pathologic precision.

The NSABP B-51/RTOG 1304 trial represents a paradigm shift in breast cancer management, showing that patients achieving nodal clearance after neoadjuvant chemotherapy derive no added benefit from regional nodal irradiation. These results challenge long-standing practice, promotes de-escalation, and raise biologically significant questions, particularly regarding immunologic mechanisms and clinical subgroup variations.