Axillary Surgery for Early-Stage, Node-Positive Mastectomy Patients and the Use of Postmastectomy Chest Wall Radiation Therapy

Sara Gaines, Nicholas Suss, Ermilo Barrera, Catherine Pesce, Kristine Kuchta, D. J. Winchester, Katharine Yao

We examined axillary surgery in mastectomy patients with tumor-positive nodes and how the type of axillary surgery impacted use of postmastectomy chest wall radiation therapy (PMRT). Using the National Cancer Data Base, we selected patients with AJCC cT1/T2c N0 breast cancer with one to three tumor-positive lymph nodes treated between 2013 and 2014. Type of axillary surgery was analyzed using the FORDS scope of regional lymph node surgery variable. Multivariable logistic regression modeling was used to identify independent predictors associated with SNB alone and the use of PMRT. Of 8089 patients, 2482 (30.7%) underwent SNB alone, 1339 (16.6%) underwent axillary dissection (ALND) alone, and 4268 (52.7%) underwent SNB followed by ALND. Fifty-seven percent of patients with micrometastases underwent SNB alone compared with 22.6% of patients with macrometastases. Independent predictors of SNB alone for patients with micrometastases were African American race, number of nodes positive, and PMRT. For patients with macrometastases, age, facility type and location, and PMRT were independent predictors for SNB alone. Of 2449 patients who underwent SNB alone, 1538 (62.8%) had no PMRT, 261 (10.7%) had PMRT alone, and 650 (26.5%) had PMRT with regional nodal irradiation. Patients undergoing SNB alone were 1.70 times [96% confidence interval (CI) 1.45-2.00] more likely to undergo PMRT than upfront ALND and 1.51 times (96% CI 1.34-1.71) more likely than SNB followed by ALND. Surgeons are omitting completion ALND in a third of early-stage, node-positive mastectomy patients. SNB alone patients are more likely to undergo PMRT than patients undergoing ALND.