Ten-Year Locoregional Recurrence Risks in Women With Nodal Micrometastatic Breast Cancer Staged With Axillary Dissection

Abstract

To compare the locoregional recurrence (LRR) rates in patients with nodal mirometastases (pNmic) with those in patients with node-negative (pN0) and macroscopic node-positive (pNmac) breast cancer; and to evaluate the LRR rates according to locoregional treatment of pNmic disease. The subjects were 9,616 women diagnosed between 1989 and 1999 with Stage pT1-T2, pN0, pNmic, or pNmac, M0 breast cancer. All women had undergone axillary dissection. The Kaplan-Meier local recurrence, regional recurrence, and LRR rates were compared among those with pN0 (n=7,977), pNmic (n=490) and pNmac (n=1,149) and according to locoregional treatment. Multivariate analysis was performed to identify the significant factors associated with LRR. The median follow-up was 11 years. The 10-year Kaplan-Meier recurrence rate in the pN0, pNmic, and pNmac cohorts was 6.1%, 6.8%, and 8.7% for local recurrence; 3.1%, 6.2%, and 10.3% for regional recurrence; and 8.0%, 11.6%, and 15.2% for LRR, respectively (all p<.001). In the pNmic patients, the 10-year regional recurrence rate was 6.4% with breast-conserving surgery plus breast radiotherapy (RT), 5.4% with breast-conserving surgery plus locoregional RT, 4.6% with mastectomy alone, 11.1% with mastectomy plus chest wall RT, and 10.7% with mastectomy plus locoregional RT. In patients with pNmic disease and age<45 years, Grade 3 histologic features, lymphovascular invasion, nodal ratio>0.25, and estrogen receptor-negative disease, the 10-year LRR rates were 15-20%. On multivariate analysis of the entire cohort, pNmic was associated with greater LRR than Stage pN0 (hazard ratio [HR], 1.6; p=.002). On multivariate analysis of pNmic patients only, age<45 years was associated with significantly greater LRR (HR, 1.9; p=.03), and trends for greater LRR were observed with a nodal ratio>0.25 (HR, 2.0; p=.07) and lymphovascular invasion (HR, 1.7; p=.07). Women with pNmic had a greater risk of LRR than those with pN0 disease. Patients with pNmic in association with young age, Grade 3 histologic features, lymphovascular invasion, nodal ratio>0.25, and estrogen receptor-negative disease experienced 10-year LRR rates of ∼15-20%, warranting consideration of locoregional RT.