Lymph node counts and ratio in axillary dissections following neoadjuvant chemotherapy for breast cancer: a better alternative to traditional pN staging.

BACKGROUND: Neoadjuvant chemotherapy (NCT) for breast cancer might change the number of involved and detected nodes in axillary lymph node dissections (ALND). In this study, we analyzed whether the number of dissected nodes and the lymph node ratio (LNR, defined as the proportion of involved nodes in dissected nodes) would have a better prognostic value than traditional pN staging.
METHODS: A total of 569 patients with stage II, III breast cancer were included in this retrospective study. All patients underwent a median of three cycles of NCT followed by mastectomy and ALND. Clinical and pathological variables were investigated using univariate and multivariate survival analyses.
RESULTS: In post-NCT node-negative (LN-) patients, those with 4-9 dissected nodes experienced a significantly lower relapse-free survival (RFS) compared with those with 10 or more dissected nodes (hazard ratio = 0.19, 0.41, for 10-19 nodes, 20+ nodes, respectively; 4-9 nodes as the reference; P = 0.002). In post-NCT node-positive (LN+) patients, a lower LNR was correlated with a better RFS on multivariate analysis, and pN staging failed to show independent prognostic significance when the LNR was included in the Cox regression model (hazard ratio = 4.2, 2.97, 2.24, and 1.68 for LNR 81-100, 61-80, 41-60; and 21-40 %, respectively; LNR 0-20 % as the reference. P < 0.001). In addition, there were significant differences in the estimated 5-year RFS for pN1 (P = 0.043) and pN3 patients (P = 0.03) among the different LNR subgroups.
CONCLUSIONS: Our study has provided new evidence that the number of dissected nodes (in LN- patients) and the LNR (in LN+ patients) might be a complementary or alternative method to traditional pN staging when evaluating disease after primary treatment.