Impact of molecular subtype on locoregional recurrence in mastectomy patients with T1-T2 breast cancer and 1-3 positive lymph nodes.

BACKGROUND: Postmastectomy radiation (PMRT) in T1-T2 tumors with 1-3 positive axillary lymph nodes (ALNs) is controversial. Impact of molecular subtype (MST) on locoregional recurrence (LRR) and PMRT benefit is uncertain. We examined the association between MST and LRR, recurrence-free survival (RFS), and overall survival (OS), in T1-T2 tumors with 1-3 positive ALNs. METHODS: From an institutional database, we identified mastectomy patients with 1-3 positive ALNs between 1995 and 2006. Patients who received neoadjuvant chemotherapy, had T3-T4 tumors, or ≥4 positive ALNs were excluded. MST was defined as: hormone receptor (HR)+/HER2-(luminal A/B), HR+/HER2+(luminal HER2), HR-/HER2+(HER2), and HR-/HER2-(basal). Kaplan-Meier method and Cox regression analysis were used to examine association between MST and LRR, RFS, and OS. RESULTS: This study included 884 patients (700 no PMRT, 141 PMRT): 72.8 % luminal A/B, 7.8 % luminal HER2, 6.8 % HER2, and 12.6 % basal. Median follow-up was 6.3 years; 39 LRRs occurred. Luminal A/B subtype had the smallest tumors (p = 0.03), lowest intraductal component (p = 0.01), histologic grade (p < 0.0001), lymphovascular invasion (LVI) (p = 0.008), and multifocality/multicentricity (p = 0.02). On univariate analyses, there was no association between MST and LRR. MST was associated with RFS and OS; the basal and HER2 subtype had the lowest RFS (p = 0.0002) and OS (p < 0.0001). On multivariate analysis, only age ≤50 years (p = 0.003) and presence of LVI (p = 0.0003) were predictive of LRR; MST was not (p = 0.38). CONCLUSION: In patients with T1-T2 breast cancer and 1-3 positive lymph nodes who did not receive PMRT, MST was not an independent predictor of LRR and may not be useful in selecting PMRT candidates in that group.

Duke Scholars

Author Alice Yoosun Ho Radiation Oncology