The impact of lymph node status on clinical outcomes following accelerated partial breast irradiation.

Abstract

107 Background: Currently, node-positive patients are considered unsuitable for APBI per the ASTRO guidelines with limited data on outcomes of node-positive patients following APBI. Methods: 510 patients with early-stage breast cancer received accelerated partial breast irradiation (APBI) between April 1993 and November 2010. Of these, 39 were lymph node positive with 10 patients having N1mi disease (median size of mets = 0.82 mm) and 29 patients having N1 disease (61.5% had 1 node positive [median size of mets = 2.5 mm], 30.8% had 2 nodes positive [median size of mets = 8.0 mm], and 7.7% had 3 nodes positive [median size of mets = 20 mm]). Patient, clinical, and pathologic factors were analyzed and compared for the node-negative (N0) and node-positive (N+) cohorts including age, tumor size, receptor status, margin status, adjuvant hormone therapy, adjuvant chemotherapy, and length of follow-up. Results: N+ patients were younger (p=0.04), had larger tumors (p<0.001), and were more likely to receive chemotherapy (p<0.001). Median follow-up was 5.3 years for N0 patients and 5.9 years for N+ patients (p=0.06). At 5 years, no differences were seen in the 5-year actuarial rates of LR (2.2% v. 2.6%, p=0.86), AR (0% v. 0%, p=0.69), DFS (90.0% v. 88.0%, p=0.79), CSS (98.0% v. 90.0%, p=0.06), or OS (91.0 v. 84.0%, p=0.65) while higher rates of RR (0% v. 6.1%, p<0.001) and DM (2.2% v. 8.9%, p=0.005) were noted in N+ patients. A total of 10 LRs occurred in the N0 patients and 1 LR in the N+ patients at a median of 2.6 and 1.5 years respectively. Both RR that developed in N+ patients were within the supraclavicular fossa at a median of 2.8 years. Univariate analysis of LR was performed and age (p=0.31), tumor size (p=0.48), ER status (p=0.13), PR status (p=0.34), T-stage (p=0.48), chemotherapy (p=0.41), APBI technique (p=0.80), and nodal status (p=0.86) were not associated with LR while there was a trend for the association of LR with close/positive margins (p=0.07), and failure to receive adjuvant hormonal therapy (p=0.06). No variables were associated with any type of AR. Conclusions: No difference was seen in the rates of local recurrence or axillary failure between node-negative and node-positive following APBI with 5-years of follow-up.