Microsatellite instability testing practices in colorectal cancer patients, in Europe and Asia

Microsatellite instability (MSI) is caused by mutations in the DNA mismatch repair genes and has been shown to predict response to checkpoint inhibitors (CPIs). Both FDA & EMA have approved CPIs in MSI-High (MSI-H) colorectal cancer (CRC). The aim of this study was to understand MSI testing practices for CRC patients, among physicians in Europe and Asia. This study was conducted using Oncology DynamicsTM, an online market research physician survey collecting drug-treated, anonymized patient data. 8,104 CRC patients in France, Germany, Italy, Spain, & UK and 4,459 CRC patients in China, Japan, & S. Korea were analyzed, in 2021, excluding clinical trials. MSI test method was available only for Q3+Q4 2021. Overall MSI testing rate was higher in Europe (44%) than Asia (35%). In Europe, the highest uptake of MSI test was observed in France and Spain at 57% and 54% testing rates, respectively. In Asia, South Korea reported the highest testing rate (68%). Among tested patients, Europe reported higher proportion (11%) of MSI-H patients compared to Asia (6%). At country level, the MSI-H patients ranged from 7-14% in Europe and 3-7% in Asia. 38% of MSI-H patients in Europe and 24% of MSI-H patients in Asia were treated with CPIs, in first-line setting. MSI test method was investigated for 1,560 patients in Europe and 782 patients in Asia, in Q3+Q4 2021. Among these patients, we have information on test method for 1,167 (75%) patients in Europe and 684 (87%) patients in Asia. In both regions, Polymerase Chain Reaction (PCR) was the predominant method of MSI detection, with 72% and 67% patient share in Europe and Asia, respectively. Next-Generation Sequencing (NGS) was used in 23-25% patients, in both regions. Highest use of NGS was observed in China (37%), followed by France (34%). This study demonstrated that testing rates are still suboptimal, reflecting barriers to testing MSI in CRC patients, in Europe and Asia. This study identifies the need for more communication and education about the benefits of testing to improve testing rates and treatment decisions. Further evaluation of the NGS adoption in clinical practice is warranted.