Disparities and trends in sentinel lymph node biopsy among early-stage breast cancer patients (1998-2005)

Background: Sentinel lymph node biopsy (SLNB), an acceptable alternative to axillary lymph node dissection for staging patients with breast cancer, was introduced to clinical practice in the late 1990s. We assessed demographic, clinical, and facility-related factors associated with SLNB in women with early-stage breast cancer and evaluated trends in these factors over time. Methods: Data on early-stage breast cancers (T1a, T1b, T1c, and T2N0) diagnosed between January 1, 1998, and December 31, 2005, were extracted from the National Cancer Database, a hospital-based registry. Patient demographics, tumor stage, type of lymph node surgery, type of breast cancer surgery, health insurance, treatment facility type, and area-level education and income variables were collected. Multivariable logistic regression analyses were performed to assess predictive factors associated with SLNB, temporal differences in factors associated with SLNB, and differences in rates of SLNB by facility type, race/ethnicity, and type of health insurance over time. Results: The total analytic study population included 490 899 women. The use of SLNB increased from 26.8% in 1998 to 65.5% in 2005. Factors associated with lower likelihood of SLNB over the study period included being older (odds ratio [OR] = 0.80, 95% confidence interval [CI] = 0.78 to 0.92 for those aged 72 or older compared with those aged 51 or younger), being of racial/ethnic minority (OR = 0.76, 95% CI = 0.74 to 0.78 for African Americans compared with whites), having no health insurance (OR = 0.77, 95% CI = 0.73 to 0.80 for uninsured compared with having private insurance), having certain government insurance plans (for Medicaid, OR = 0.81, 95% CI = 0.78 to 0.84, and for Medicare at age <65 years, OR = 0.83, 95% CI = 0.80 to 0.87, both compared with private insurance), residing in zip codes with lower proportion of high school graduates (OR = 0.88, 95% CI = 0.86 to 0.89) or with lower median income (OR = 0.79, 95% CI = 0.77 to 0.81), and receiving treatment in facility types other than a teaching or research hospital (for community hospital, OR = 0.84, 95% CI = 0.82 to 0.86; for community cancer center, OR = 0.86, 95% CI = 0.84 to 0.87). The associations with insurance status and sociodemographic characteristics were more pronounced in 2005 than in 1998. For example, the adjusted annual rates of SLNB in 1998 were 0.29 in whites, 0.26 in African Americans, and 0.35 in Hispanics; in 2005 the respective rates were 0.70, 0.64, and 0.67. Conclusions: Although use of SLNB increased from 1998 to 2005, disparities persisted in receipt of SLNB that are based on nonclinical factors, including sociodemographic characteristics and insurance status.