Impact of lymph node ratio (LNR) on prognosis of early breast cancer.

Abstract

1115 Background: Breast cancer is currently staged according to the TNM (tumors, nodes, metastases) classification of the American Joint Committee on Cancer (AJCC) Staging System. Lymph node ratio (LNR, the ratio of positive axillary lymph nodes to the total number of nodes examined) may provide additional prognostic information to that provided by TNM scores. Furthermore, LNR may potentially identify subpopulations within the traditional AJCC stages that are at increased risk of adverse outcomes. Methods: We performed a single institution retrospective study of all patients diagnosed with early breast cancer between January 2000 and January 2011. Patients were divided into low- (≤0.14), intermediate- (0.15-0.39) and high-risk (≥0.4) LNR groups. We assessed the impact of LNR and conventional AJCC staging parameters on overall survival (OS) and disease-free survival (DFS). Results: 786 patients were included in the analsyis, 238 of whom were node positive. As expected nodal status according to pathologic nodal (pN) stage was prognostic for OS and DFS with OS decreasing from 88.3% in pN1 patients to 40.8% in those with pN3 disease (p<0.001). LNR was also significantly associated with prognosis. OS decreased from 94% in the low-risk LNR group to 64% in the high-risk group, while DFS decreased from 92% in the low-risk LNR group to 50% in the high-risk (p<0.001). When Stage III patients were divided into low- and high-risk LNR groups, OS decreased from 100% in the low LNR group to 63% in the high LNR group (p<0.05). Similarly, DFS decreased from 96% in the low LNR group to 56% in the high LNR group (p<0.05). A similar trend was not observed when Stage III patients were stratified according to pN status. LNR was also found to be prognostic when pN1 patients were divided into low- and high-risk LNR groups. Although both LNR and nodal status were significantly associated with OS and DFS on univariate analysis, LNR retained its significance on multivariate analysis, while nodal status did not. Conclusions: LNR can identify subpopulations within the traditional AJCC staging that are at higher risk of adverse outcomes. These findings should be examined in larger retrospective studies and, if validated, be considered as a stratification factor in future adjuvant trials.