Outcomes of node-negative breast cancer 5 centimeters and larger treated with and without postmastectomy radiotherapy

Abstract

Purpose: The role of adjuvant postmastectomy radiotherapy (PMRT) remains controversial for the rare presentation of pT3pN0cM0 breast cancer. The present analysis examined locoregional recurrence (LRR) and breast cancer-specific survival (BCSS) in pT2 = 5.0-cm and pT3 >5.0-cm tumors treated with mastectomy, stratified by PMRT use.

Materials and methods: Between January 1, 1989 and December 31, 2000, the British Columbia provincial database yielded 100 node-negative patients with tumors ≥ 5 cm of 19,846 nonmetastatic breast cancer patients (0.5%). Of these 100 patients, 44 (44%) had received adjuvant PMRT.

Results: The PMRT group contained significantly more pT3 >5-cm cases (p = 0.001) and margin-positive cases (p = .03). With a median follow-up of 10 years, the cumulative 10-year LRR rate was 2.3% (95% confidence interval, 0.2-10.5) in the PMRT group vs. 8.9% (95% confidence interval, 3.2-18.2) in the no-PMRT group (p = .2). Regarding LRR in the no-PMRT group, all patients had Grade 3 histologic features (LRR 17%, 5 of 29) and had not received hormonal therapy (LRR 15%, 5 of 34). The 10-year breast cancer-specific survival rate was 85.8% (95% confidence interval 71.0-93.4) in the PMRT group vs. 74.6% (95% confidence interval 59.9-84.5) in the no-PMRT group (p = .2). On multivariate analysis, adjusted for the prognostic and predictive variables, PMRT did not significantly improve the LRR or breast cancer-specific survival rates.

Conclusion: The present study demonstrated a low LRR rate for node-negative breast cancer ≥ 5 cm. Our results indicate that PMRT should be considered for Grade 3 histologic features and patients not undergoing hormonal therapy.