The role of post-mastectomy radiotherapy (PMRT) in T1-T2 node negative breast cancer remains unclear. The aim of this study was to determine the impact of PMRT in relation to the number of examined axillary nodes.
This is a retrospective study, based on a cohort including breast carcinoma patients recorded in two centers of Omid and Imamreza Hospital of Mashhad University of Medical Sciences, Iran, from 1991 to 2012. All patients with N0 and T1-T2 tumors that had undergone modified radical mastectomy were included. Patients were categorized into two groups of with and without PMRT. Overall survival (OS) was the end point of study. The age, tumor grade, estrogen receptor status, human epidermal growth factor receptor 2 status, taking chemotherapy and hormontherapy as well as the number of examined axillary nodes were compared in two groups. To evaluate the minimum acceptable examined nodes, two different cutoff, ≤3 nodes vs. >3 nodes and ≤6 nodes vs. >6 nodes were considered.
Five hundred and three patients were eligible in two groups including 199 patients in the group without PMRT, and 304 patients in the group with PMRT. The median follow up was 60 months. Overall no survival benefit was seen for adjuvant radiotherapy. The 5 and 10-year OS of two groups were respectively 86% and 82% without PMRT and 90% and 86% with PMRT (P = 0.5). Regression analysis showed the only prognostic factor is the variable of ≤3 vs. >3 nodes (P= 0.01). Other variables including the ≤6 vs. >6 nodes did not have a significant effect on outcome. However analysis showed without PMRT the 5 and 10-year OS of 44 patients with ≤3 examined nodes were respectively 76% and 63%, and the 5 and 10-year OS of 155 patients with >3 examined nodes were 89% and < 89% (P= 0.02). In the group with PMRT the 5 and 10-year OS of 102 patients with ≤3 examined nodes were respectively 82% and 77% and the 5 and 10-year OS of 202 patients with >3 examined nodes were 92% and 88% (P = 0.056).
According to the results of this study in node negative T1-T2 breast cancer axillary node pick up of less than 4 is an important negative prognostic factor. PMRT can improve the outcome of a suboptimal dissection and is recommended as a cutoff point if less than 4 nodes have been examined.
Clinical trial identification
All authors have declared no conflicts of interest.