Background: Next-Generation Sequencing (NGS) based genomic testing is one of the key drivers of precision medicine in US Oncology practices. Studies of utilization of NGS testing via insurance claims have been challenged by widely variable and nonspecific coding and billing. We sought to (1) characterize the variation in code usage for Multi-Gene Tumor Panel Testing (MGPT) and tests that include assessment of Tumor Mutation Burden (TMB) and (2) apply knowledge of this variation to measure real-world utilization of MGPT and TMB tests. Methods: Using proprietary claims matching algorithms to identify MGPT and TMB tests, reimbursed medical claims submitted to a major insurance provider from Q2 2017 to Q1 2018 were analyzed to understand utilization rate (tests per 1000 members per year, TMY), geographical distribution and CPT coding variability for MGPT and TMB tests among Oncology patients. Results: Among 37 M medical claims submitted between Q2 2017 and Q1 2018, we found 764,236 medical claims related to genetic testing in adults. Utilization rates for TMB and MGPT were 0.12 and 1.40 per 1000 members per year, respectively. Numerous billing code combinations were used for both MGPT and TMB tests, with the number of billed CPT codes ranging from 34 (across TMB tests in Breast Cancer patients) to 85 (across MGPT in Colorectal patients). CPT coding variability, measured as the number of unique CPT signatures across medical claims, was found to be higher for MGPT compared to TMB tests in patients diagnosed with Lung (494 vs. 215), Colorectal (447 vs. 214) and Breast (295 vs. 121) Cancers. Test utilization rates were found to be increasing with age and higher in females compared to males for TMB (0.14 vs. 0.10 TMY) and MGPT (1.57 vs. 1.22 TMY). Utilization rates for both test types by region (MidAtlantic, Midwest, Northeast, South and West) were 0.16, 0.13, 0.04, 0.12 and 0.09 per 1000 members per year, respectively. Conclusion: This study provided an initial understanding of patterns in utilization of genomic testing in the US. Real-world data on trends in genomic testing may provide insights on the current status of cancer care and thus guide healthcare providers as well as enable treatment pathways in delivering value-based care. CPT coding variability observed in this study highlights the need for standardization of coding guidelines to achieve a value-based practice system and improve the quality of patient care across U.S. oncology practices.