Better survival in PMRT of female breast cancer patients with >5 negative lymph nodes: A population-based study.

Many studies have confirmed the role of postmastectomy radiotherapy (PMRT) for breast cancer patients with at least 4 lymph nodes invasion in the postoperative therapy. Recently, the number of negative lymph nodes (NLNs) has been increasingly paid attention to and recognized as a prognostic indicator in different kinds of caners. Therefore, it is very necessary to study the association between the number of NLNs and the prognosis of PMRT in breast cancer patients. In our study, we used Surveillance, Epidemiology, and End Results (SEER) population-based data and identified 16,686 breast cancer patients to explore their correlation. The ROC curve and the log-rank χ test were applied to determine the appropriate cutoff point of the number of NLNs and 5 was selected as the cutoff point. Furthermore, the cutoff point 5 was validated as an independent prognostic factor affecting cancer-specific survival (CSS) and overall survival (OS) in breast cancer patients, as confirmed by both univariate and multivariate analysis (P < 0.001). In addition, subgroup analysis showed that the number of NLNs >5 can be a prognostic indicator in patients with PMRT according to different clinical variables (all, P < 0.001). Importantly, our results showed that PMRT obviously improved CSS and OS in patients regardless of the number of NLNs (P < 0.001). In conclusion, our study showed the number of NLNs is an independent prognostic factor for breast cancer patients with PMRT, and those who have higher number of NLNs have an increased CSS and OS.