Background: The purpose of the present study was to retrospectively evaluate the effects of extracapsular extension (ECE) on the benefits of post-mastectomy radiation therapy (PMRT) for groups of patients with varying numbers of positive axillary nodes (1-3, 4-9 and ≥10 positive axillary nodes).
Methods: A total of 1220 axillary node-positive patients who had received mastectomy were involved in this study. Patients were grouped as 'Radio + /ECE + ', 'Radio-/ECE + ', 'Radio + /ECE-' or 'Radio-/ECE-' according to status of ECE and whether receiving PMRT or not, and were evaluated in terms of local region relapse (LRR) rate. The 5-year and 10-year Kaplan-Meier disease-free survival and overall survival (OS) rates were analyzed.
Results: ECE-positive differed from ECE-negative groups with statistical significance for all comparisons in favor of the ECE-negative group: 5-year locoregional failure-free survival (LRFFS) (82.69% vs 91.83%, P < 0.001), 10-year LRFFS (75.39% vs 90.02%, P < 0.001); 5-year OS (52.12% vs 74.46%, P < 0.001), 10-year OS (35.17% vs 67.63%, P < 0.001). There were no significant effects of ECE on the benefits of PMRT for patients with 1-3 (P = 0.5720), ≥10(P = 0.0614) positive axillary nodes. However, for the group of patients with 4-9 positive axillary nodes, ECE status had a significant effect on the benefits of PMRT with respect to 5-year and 10-year LRFFS (P < 0.05).
Conclusion: In our study, regardless of the ECE status, PMRT didn't significantly improve the LRFFS for patients with 1-3 or ≥10 positive axillary nodes. However, for patients with 4-9 positive axillary nodes, ECE could be an important criterion to consider when deciding whether to receive PMRT.
Keywords: ECE; PMRT; breast neoplasms; prognosis.