Outcomes of Clinically Node-Negative Breast Cancer Without Axillary Dissection: Can Preserved Axilla Be Safely Treated with Radiation after a Positive Sentinel Node Biopsy?

Purpose: We analyzed whether axillary nodal irradiation could control clinically node-negative disease, including those patients with a positive sentinel lymph node biopsy (SLNB), most of whom received regional nodal irradiation. We also evaluated toxicity profiles that resulted from nodal irradiation. Patients and Methods: From 1988 to 2011, 2107 patients with cT1-T2N0M0 breast cancer underwent breast conservation therapy in the absence of axillary dissection: nx group (n = 1548), without any axillary surgery; the sn^- group (n = 518), with a negative SLNB; and sn⁺ group (n = 104), with a positive SLNB. Results: The median follow-up times were 88, 56, and 55 months for the nx, sn^-, and sn⁺ groups, respectively. The nx group had more risk factors than did the other 2 groups in terms of age, grade, or T stage. Ninety-eight percent of the sn^-group received only tangent irradiation, and 100% and 83% of the sn⁺ and nx group, respectively, received additional regional nodal irradiation. The 5-year cumulative incidences of axillary failure and regional nodal failure were 34, 3, and 0 (2.7%, 0.7%, and 0%; P =.02, log-rank test) and 57, 4, and 0 (4.4, 1%, and 0; P =.04), respectively. Overall survival rates in 5 years were 96.4%, 98.9%, and 97.6% (P =.03), respectively. Symptomatic but transient radiation pneumonitis developed in 31, 16, and 6 (2.0%, 3.1%, and 5.7%). Mild arm edema was observed in 1, 4, and 0 (0.06%, 0.8%, and 0%) in the nx, sn^-, sn⁺ groups, respectively. Conclusions: Treatment without axillary dissection showed excellent outcomes with negligible toxicity for patients with clinically node negative, including those with a positive SLNB. Regional nodal irradiation after a positive SLNB is a reasonable alternative to axillary dissection.