Prognosis of residual axillary disease after neoadjuvant chemotherapy in clinically node-positive breast cancer patients: isolated tumor cells and micrometastases carry a better prognosis than macrometastases

Purpose: The aim of this study was to compare disease-free survival (DFS) and overall survival (OS) between clinically node-positive breast cancer patients, treated with neoadjuvant chemotherapy (NAC), with axillary pathologic complete response (ypN0), residual axillary isolated tumor cells or micrometastases (ypNitc/mi), and residual axillary macrometastases (ypN1-3). Methods: All patients diagnosed with clinically node-positive primary invasive breast cancer treated with NAC and subsequent axillary lymph node dissection between 2005 and 2008 were retrospectively analyzed. Data were obtained from the Netherlands Cancer Registry. Patients were stratified by final pathological axillary status: ypN0, ypNitc/mi, or ypN1-3. The main outcome measures DFS and OS were analyzed using Kaplan–Meier survival analysis. Uni- and multivariable cox regression analyses were used to determine independent predictors for DFS and OS. Results: A total of 1347 patients were included. Pathologic nodal status was ypN0 in 22.2%, ypNitc/mi in 3.8%, and ypN1-3 in 74.0% of patients. Overall, 5-year DFS was 57.8% and mean OS was 7.4 years. DFS and OS were comparable between ypN0 and ypNitc/mi (HR 1.38 (0.40–4.79, p = 0.613) and HR 0.92 (0.27–3.09, p = 0.889), respectively), but significantly different between ypN0 and ypN1-3 (HR 1.78 (1.06–3.00, p = 0.031) and HR 1.70 (1.07–2.71, p = 0.026), respectively). Conclusions: Clinically node-positive patients, treated with NAC, with axillary nodal status ypN0 or ypNitc/mi carry similar prognosis regarding DFS and OS. Axillary nodal status ypN1-3 is associated with a less favorable prognosis. Future studies should consider ypN0 and ypNitc/mi as one entity.