Radiation therapy and survival in breast cancer patients with 10 or more positive axillary lymph nodes treated with mastectomy.

PURPOSE: Adjuvant loco-regional radiation (XRT) frequently is recommended after mastectomy and adjuvant systemic therapy in patients with 10 or more positive axillary lymph nodes (ALN) to reduce the high loco-regional failure rate observed in this subset. In this study, we explored the possibility that adjuvant loco-regional radiation therapy (LR-XRT) also could decrease distant failure and improve overall survival (OS) in this subset of poor-prognosis patients. PATIENTS AND METHODS: Retrospectively, 618 breast patients with 10 or more positive ALN were studied. The median follow-up time was 7.5 years. All patients received systemic adjuvant therapy and 35% also received adjuvant radiation therapy. Loco-regional failure, distant failure, and OS analyses were adjusted for age, tumor size, number of positive ALN, and estrogen receptor (ER) status using Cox regression model.
RESULTS: As expected, patients had a very high risk of loco-regional and distant failure. At 5 years, 30% of patients had loco-regional failure as a first event and 54% had distant failure. Radiation dramatically reduced loco-regional failure (hazards rate ratios [RR]=0.29; 95% confidence interval [CI], 0.19 to 0.45). The adjusted 5-year loco-regional failure rate was 13% with radiation and 38% without radiation (P=.0001). Radiation also was associated with improved distant control (RR=0.75; 95% CI, 0.58 to 0.96). The adjusted 5-year distant failure rate was 48% with radiation and 58% without radiation (P=.02). OS also improved with radiation (RR=0.68; 95% CI, 0.53 to 0.85). The adjusted 5-year OS was 56% with radiation and 42% without radiation (P=.001).
CONCLUSION: In this cohort of high-risk breast cancer patients, XRT was associated with less loco-regional and distant failure and improved OS. This suggests that improved loco-regional control might decrease secondary systemic spread and improve survival.