Geographic and site variability in the treatment of patients with metastatic gastric cancer.

153Background: Previous work has demonstrated substantial heterogeneity in the treatment of metastatic gastric cancer (mGC) in the U.S. across all lines of therapy. However, the distribution of variability by region and clinical practice site is not well understood. Methods: De-identified patient-level electronic medical record (EMR) and claims data from IMS Oncology EMR and from Truven Marketscan, respectively, were used for this study. Eligible patients were age ≥ 18 years with newly diagnosed GC between 2007 and 2014. Metastases were identified by ICD-9 codes in the EMR and claims data or with evidence of stage IV or M1 disease in EMR. Patients classified with locally advanced/advanced disease were those who received chemotherapy without surgical intervention following diagnosis, regardless of absence or presence of metastases. Variability of treatment by line of therapy was measured by the Herfindahl-Herschman Index (HHI), a commonly used measure of market concentration in the business sector. The HHI...