OUTCOMES OF NODE-NEGATIVE BREAST CANCER 5 CENTIMETERS AND LARGER TREATED WITH AND WITHOUT POSTMASTECTOMY RADIOTHERAPY

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.