Underuse of axillary dissection for the management of sentinel node micrometastases in breast cancer.

BACKGROUND Current American Society of Clinical Oncology guidelines for management of sentinel node micrometastases (SNMM) in breast cancer recommend axillary lymph node dissection (ALND) for all patients. OBJECTIVE To assess nationwide use of ALND for SNMM. DESIGN Population-based retrospective observational study. SETTING The National Cancer Institute's Surveillance, Epidemiology, and End Results database (1998-2005). PATIENTS Five thousand three hundred fifty-three patients with SNMM. MAIN OUTCOME MEASURE Use of ALND after identification of SNMM. RESULTS The prevalence of SNMM increased from 2.5% in 1998 to 17.7% in 2005. Of 5353 patients with SNMM, 2160 (40.4%) had no further nodal surgery and 3193 (59.6%) underwent ALND. In the latter group, histopathologic examination of nonsentinel nodes upstaged 18.6% of cases to N1, 2.2% to N2, and 0.1% to N3 disease. Multivariate analysis using logistic regression showed that age younger than 66 years (odds ratio [OR], 1.79; 95% confidence interval [CI], 1.56-2.04), high tumor grade (OR, 1.22; 95% CI, 1.07- 1.40), and tumor size larger than 2 cm (OR, 1.16; 95% CI, 1.01-1.32) were predictive of ALND. Predictors of upstaging were infiltrating lobular histology (OR, 1.23; 95% CI, 1.00-1.51), T2 stage (OR, 1.38; 95% CI, 1.14-1.67), T3 stage (OR, 3.66; 95% CI, 1.70-7.90), and number of nodes examined (OR, 1.04; 95% CI, 1.03-1.05). CONCLUSIONS Only 60% of patients with SNMM from breast cancer are treated according to American Society of Clinical Oncology guidelines. Nodal staging based only on sentinel node biopsy may underestimate the extent of nodal disease in 20.9% of cases. Surgical management of SNMM should be standardized.