Site variation in assessment of biomarkers on biopsy specimens in patients with metastatic disease.

Background: Clinical practice guidelines in patients with metastatic breast cancer recommend assessment of biomarkers-estrogen receptors (ER), progesterone receptors (PR), and HER2-on metastatic lesions. The purpose of this study was to identify factors associated with assessment of these biomarkers in patients who had undergone confirmatory biopsies. We were particularly interested in variation between treatment sites. Methods: Eligible patients were those diagnosed with metastatic breast cancer who had undergone a confirmatory biopsy and who were part of the Michigan Breast Oncology Quality Initiative (MiBOQI) registry, a statewide registry of 25 health systems. Analyses investigated associations between assessment of ER, PR, HER2 and treating center, disease, clinical and non-clinical factors. Results: Between 2006 and 2015, 805 patients had a confirmatory biopsy. Of these, 66% had ER, 63% had PR, 62% had HER2, and 57% had all three assessed on the biopsy specimen. In bivariate analysis, characteristics associated with assessment of biomarkers were earlier stage and hormone receptor-positive primary tumors, private or military insurance, white race, longer time since initial diagnosis, and bone only, liver only, lung only, chest wall, skin, and lymph nodes, and multiple sites of metastases. Younger age was positively associated with assessment of HER2. Biomarker assessment also varied significantly between treatment sites and increased over time. In multivariate analyses, time since diagnosis of the primary (p \u3c 0.001) and treatment site (p \u3c 0.001) remained significant. With the exception of ER (p = 0.09), performance of biomarkers increased significantly over time. Conclusions: Across 25 health systems in a quality improvement collaborative, the proportion of patients with metastatic disease who underwent a confirmatory biopsy increased over time. Nonetheless, treatment site continued to be independently associated with the odds of having biomarkers assessed on biopsy specimens. Our findings suggest that there are opportunities for improvement to provide guideline-concordant care in patients treated in diverse settings