Background:To test the hypotheses that breast cancer patients with one to three positive lymph nodes (pN1) consist of heterogeneous prognostic subsets and that the ratio of positive nodes to total nodes dissected (lymph node ratio, LNR) might discriminate patients with a higher risk as candidates for post-mastectomy radiation therapy (PMRT).Methods:Using information from 7741 node-positive patients, we first identified cutoff values of the LNR using the nonparametric bootstrap method. Focusing on 3477 patients with pN1 disease, we then evaluated the clinical relevance of the LNR categorised by the estimated cutoff values (categorised LNR, cLNR).Results:Among 3477 patients with pN1 disease, 3059 and 418 patients were assigned into the low and intermediate cLNR groups, respectively, based on a cutoff value of 0.18. The prognostic factors associated with poor overall survival (OS) included younger age, T2 stage, negative oestrogen/progesterone receptors, high histologic grade, and intermediate cLNR. Post-mastectomy radiation therapy significantly increased OS in patients assigned to the intermediate cLNR (hazard ratio, 0.39; 95% confidence interval, 0.17-0.89; P=0.0248), whereas patients in the low cLNR group derived no additional survival benefit from PMRT.Conclusion:This study suggests that PMRT should be recommended for patients with pN1 disease and an intermediate cLNR.
Bibliographical noteFunding Information:
Statistics. The primary end point of this study was overall survival (OS) defined as the time from the date of surgery to death of any cause. According to the Akaike Information Criteria, the independent prognostic factors significantly associated with OS were selected in stepwise manner avoiding over-parameterisation. The treatment effect of PMRT in patients with pN1 disease was assessed for each of the cLNR groups using the likelihood ratio test. Based on the log-rank test, the Kaplan–Meier OS estimates of the cLNR groups were also compared with measure, the unadjusted treatment effects of PMRT. P-values <0.05 were considered statistically significant. All statistical analyses were performed using R (http://www.r-project.org). This study was approved by the Korean Breast Cancer Registry Committee and the Institutional Review Boards of Severance Hospital.
All Science Journal Classification (ASJC) codes
- Cancer Research