Socioeconomic Determinants of the Use of Molecular Testing in Stage IV Colorectal Cancer

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Abstract
Objectives: Treatment with epidermal growth factor receptor monoclonal antibodies extends life for patients with advanced colorectal cancers (CRCs) whose tumors exhibit wild-type KRAS, but KRAS testing may be underused. We studied the role of socioeconomic factors in the application of KRAS testing. Materials and Methods: We identified subjects with stage IV colorectal adenocarcinoma diagnosed 2010-2015 in the Surveillance, Epidemiology, and End Results (SEER) database. We used multivariable logistic regression models to evaluate associations between clinical/demographic factors and the rate of KRAS testing. We used multivariable-adjusted Cox proportional hazards models to assess survival. Results: We identified 37,676 patients with stage IV CRC, 31.1% of whom were tested for KRAS mutations, of those who had documented KRAS testing, 44% were KRAS mutant. Patients were more likely to be tested if they were younger (odds ratio [OR]=5.10 for age 20 to 29 vs. 80+, 95% confidence interval [CI]: 3.99-6.54, PP$69,311 vs. <$49,265, 95% CI: 1.14-1.35, PPPP<0.01). Conclusions: We found a low rate of KRAS testing in CRC patients with those living in low-income areas less likely to be tested, even after controlling for Medicaid insurance. Our study suggests that socioeconomic disparities persist despite Medicaid insurance.

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