Patterns and predictors of breast cancer chemotherapy use in Kaiser Permanente Northern California, 2004–2007

Chemotherapy regimens for early stage breast cancer have been tested by randomized clinical trials, and specified by evidence-based practice guidelines. However, little is known about the translation of trial results and guidelines to clinical practice. We extracted individual-level data on chemotherapy administration from the electronic medical records of Kaiser Permanente Northern California (KPNC), a pre-paid integrated healthcare system serving 29 % of the local population. We linked data to the California Cancer Registry, incorporating socio-demographic and tumor factors, and performed multivariable logistic regression analyses on the receipt of specific chemotherapy regimens. We identified 6,004 women diagnosed with Stage I–III breast cancer at KPNC during 2004–2007; 2,669 (44.5 %) received at least one chemotherapy infusion at KPNC within 12 months of diagnosis. Factors associated with receiving chemotherapy included <50 years of age [odds ratio (OR) 2.27, 95 % confidence interval (CI) 1.81–2.86], tumor >2 cm (OR 2.14, 95 % CI 1.75–2.61), involved lymph nodes (OR 11.3, 95 % CI 9.29–13.6), hormone receptor-negative (OR 6.94, 95 % CI 4.89–9.86), Her2/neu-positive (OR 2.71, 95 % CI 2.10–3.51), or high grade (OR 3.53, 95 % CI 2.77–4.49) tumors; comorbidities associated inversely with chemotherapy use [heart disease for anthracyclines (OR 0.24, 95 % CI 0.14–0.41), neuropathy for taxanes (OR 0.45, 95 % CI 0.22–0.89)]. Relative to high-socioeconomic status (SES) non-Hispanic Whites, we observed less anthracycline and taxane use by SES non-Hispanic Whites (OR 0.63, 95 % CI 0.49-0.82) and American Indians (OR 0.23, 95 % CI 0.06–0.93), and more anthracycline use by high-SES Asians/Pacific Islanders (OR 1.72, 95 % CI 1.02–2.90). In this equal-access healthcare system, chemotherapy use followed practice guidelines, but varied by race and socio-demographic factors. These findings may inform efforts to optimize quality in breast cancer care.