Impact of lymph node status on clinical outcomes after accelerated partial breast irradiation

To compare outcomes after accelerated partial breast irradiation (APBI) between node-negative and node-positive patients.

A total of 534 patients with early-stage breast cancer received APBI including 39 node-positive (N+) cases. Clinical, pathologic, and treatment-related factors were compared between node-negative (N-) and N+ cohorts. Local recurrence (LR), regional recurrence (RR), axillary failure (AF), distant metastases (DM), disease-free survival (DFS), cause-specific survival (CSS), and overall survival (OS) were analyzed.

N+ patients were younger (p = 0.04), had larger tumors (p < 0.001), and were more likely to receive chemotherapy (p < 0.001). Mean follow-up was 7.8 years for N+ patients and 6.3 years for N- patients (p = 0.06). No differences were seen in 5-year actuarial rates of LR (2.2% vs. 2.6%, p = 0.86), AF (0% vs. 0%, p = 0.69), DFS (90.0% vs. 88.0%, p = 0.79), or OS (91.0 vs. 84.0%, p = 0.65) between the two groups, whereas higher rates of RR (0% vs. 6.1%, p < 0.001) and DM (2.2% vs. 8.9%, p = 0.005) were noted in N+ patients. A trend for improved CSS (p = 0.06), was seen in N- patients. Age, tumor size, receptor status, T-stage, chemotherapy, APBI technique, and nodal status (p = 0.86) were not associated with LR, while a trend for an association with LR was noted with close/positive margins, (p = 0.07), and failure to receive adjuvant hormonal therapy (p = 0.06).

No differences were seen in the rates of LR or AF between N- and N+ patients after APBI. These results support the continued enrollment of node-positive patients in Phase III trials evaluating the efficacy of APBI including the National Surgical Adjuvant Breast and Bowel Project-B39/Radiation Therapy Oncology Group 0413.