Biomarker testing, treatment patterns and outcomes in previously treated pMMR or non-MSI-H metastatic colorectal cancer patients.

Aim: To assess biomarker testing utilization, treatment patterns, and clinical outcomes in previously treated proficient mismatch repair deficient (pMMR) or non-microsatellite instability-high (MSI-H) metastatic colorectal cancer (mCRC) patients.

Materials & Methods: Using the iKnowMed electronic health record database, this study included pMMR/non-MSI-H adult mCRC patients previously treated with standard-of-care (SoC) chemotherapies between 1 January 2016 and 31 December 2021. Patients were censored for overall survival (OS) and real-world progression-free survival (rwPFS) at their last visit date or the end of study period, 31 August 2022.

Results: MSI/MMR testing was conducted in 70.9% of mCRC patients. In 292 previously treated mCRC patients, 69.5% received SACT (regorafenib:14.8%, trifluridine+tipiracil (TAS-102):12.3%, other SACT:72.9%), 28.8% received BSC and 1.7% received no BSC/SACT. The most common other SACT included irinotecan- (37.4%) and oxaliplatin-based (14.8%) therapies. The most patients were tested for KRAS (89%) and BRAF (81%). Overall, the median (95% CI) OS and rwPFS was 7.4(5.8,8.8) and 3.5(3.2,4.3) months, respectively.

Conclusions: Only 70.9% of mCRC patients received guideline-recommended MSI/MMR testing, indicating a need for improved testing rates. Additionally, only 27.1% of previously treated mCRC patients received SoC options (regorafenib/TAS-102). The real-world variability in treatment choices and a high rate of chemotherapy rechallenge in subsequent lines highlight an unmet need in this patient population.