We sought to determine present-day locoregional recurrence (LRR) rates to better understand the role of postmastectomy radiotherapy (PMRT) in women with 0 to 3 positive lymph nodes.

Clinical and pathologic factors were identified for 1019 patients with pT1 or pT2 tumors and 0 (n = 753), 1 (n = 176), 2 (n = 69), or 3 (n = 21) positive lymph nodes treated with mastectomy without PMRT during 1997 to 2002. Total LRR rates were calculated by Kaplan-Meier analysis and compared between subgroups by the log rank test.

After a median follow-up of 7.47 years, the overall 10-year LRR rate was 2.7%. The only independent predictor of LRR was younger age (P = 0.004). Patients ≤40 years old had a 10-year LRR rate of 11.3 vs. 1.5% for older patients (P < 0.0001). The 10-year rate of LRR in patients with 1 to 3 positive nodes was 4.3% (94.4% had systemic therapy), which was not significantly different from the 10-year risk of contralateral breast cancer development (6.5%; P > 0.5). Compared with the 10-year LRR rate among patients with node-negative disease (2.1%), patients with 1 positive node had a similar 10-year LRR risk (3.3%; P > 0.5), and patients with 2 positive nodes had a 10-year LRR risk of 7.9% (P = 0.0003). Patients with T2 tumors with 1 to 3 positive nodes had a 10-year LRR rate of 9.7%.

In patients with T1 and T2 breast cancer with 0 to 3 positive nodes, LRR rates after mastectomy are low, with the exception of patients ≤40 years old. The indications for PMRT in patients treated in the current era should be reexamined.