The purpose of this study was to determine local-regional recurrence (LRR) risk according to whether postmastectomy radiation therapy (PMRT) was used to treat breast cancer patients with clinical T3N0 disease who received neoadjuvant chemotherapy (NAC) and mastectomy.

Clinicopathology data from 162 patients with clinical T3N0 breast cancer who received NAC and underwent mastectomy were retrospectively reviewed. A total of 119 patients received PMRT, and 43 patients did not. The median number of axillary lymph nodes (LNs) dissected was 15. Actuarial rates were calculated using the Kaplan-Meier method and compared using the log-rank test.

At a median follow-up of 75 months, 15 of 162 patients developed LRR. For all patients, the 5-year LRR rate was 9% (95% confidence interval [CI], 4%-14%). The 5-year LRR rate for those who received PMRT was 4% (95% CI, 1%-9%) vs. 24% (95% CI, 10%-39%) for those who did not receive PMRT (p <0.001). A significantly higher proportion of irradiated patients had pathology involved LNs and were ≤40 years old. Among patients who had pathology involved LNs, the LRR rate was lower in those who received PMRT (p <0.001). A similar trend was observed for those who did not have pathology involved LN disease. Among nonirradiated patients, the appearance of pathologic LN disease after NAC was the only clinicopathologic factor examined that significantly correlated with the risk of LRR.

Breast cancer patients with clinical T3N0 disease treated with NAC and mastectomy but without PMRT had a significant risk of LRR, even when there was no pathologic evidence of LN involvement present after NAC. PMRT was effective in reducing the LRR rate. We suggest PMRT should be considered for patients with clinical T3N0 disease.