Impact of postmastectomy radiation on locoregional recurrence in breast cancer patients with 1-3 positive lymph nodes treated with modern systemic therapy

Abstract

Purpose: Postmastectomy radiation therapy (PMRT) remains controversial for patients with 1-3 positive lymph nodes (LN+).

Methods and materials: We conducted a retrospective review of all 369 breast cancer patients with 1-3 LN+ who underwent mastectomy without neoadjuvant systemic therapy between 2000 and 2007 at Cleveland Clinic.

Results: We identified 271 patients with 1-3 LN+ who did not receive PMRT and 98 who did receive PMRT. The median follow-up time was 5.2 years, and the median number of LN dissected was 11. Of those not treated with PMRT, 79% received adjuvant chemotherapy (of whom 70% received a taxane), 79% received hormonal therapy, and 5% had no systemic therapy. Of the Her2/neu amplified tumors, 42% received trastuzumab. The 5-year rate of locoregional recurrence (LRR) was 8.9% without PMRT vs 0% with PMRT (P=.004). For patients who did not receive PMRT, univariate analysis showed 6 risk factors significantly (P<.05) correlated with LRR: estrogen receptor/progesterone receptor negative (hazard ratio [HR] 2.6), lymphovascular invasion (HR 2.4), 2-3 LN+ (HR 2.6), nodal ratio >25% (HR 2.7), extracapsular extension (ECE) (HR 3.7), and Bloom-Richardson grade III (HR 3.1). The 5-year LRR rate was 3.4% (95% confidence interval [CI], 0.1%-6.8%] for patients with 0-1 risk factor vs 14.6% [95% CI, 8.4%-20.9%] for patients with ≥2 risk factors (P=.0006), respectively. On multivariate analysis, ECE (HR 4.3, P=.0006) and grade III (HR 3.6, P=.004) remained significant risk factors for LRR. The 5-year LRR was 4.1% in patients with neither grade III nor ECE, 8.1% with either grade III or ECE, and 50.4% in patients with both grade III and ECE (P<.0001); the corresponding 5-year distant metastasis-free survival rates were 91.8%, 85.4%, and 59.1% (P=.0004), respectively.

Conclusions: PMRT offers excellent control for patients with 1-3 LN+, with no locoregional failures to date. Patients with 1-3 LN+ who have grade III disease and/or ECE should be strongly considered for PMRT.