Real-World Treatment Patterns and Clinical Outcomes for Standard of Care Regimens in Patients with Deficient MMR or MSI-High Metastatic Colorectal and Non-Colorectal Cancer: A Retrospective Chart Review Study in France

Introduction There is limited evidence on the effectiveness of standard of care (SOC) treatments in previously treated patients with deficient mismatch repair (dMMR) or microsatellite instability high (MSI-H) metastatic cancer. Immune checkpoints inhibitors (ICIs) have emerged as key treatments for dMMR/MSI-H tumors. However, clinical outcomes data with SOC regimens are still limited. Study objectives were to evaluate real-world treatment patterns and clinical outcomes in patients with dMMR/MSI-H metastatic colorectal cancer (mCRC) and non-CRC receiving SOC regimens. Given the resulting small cohort of patients with metastatic non-CRC, only summary results are provided. Methods Two French university hospitals participated in a retrospective chart review study in which adult patients with dMMR/MSI-H mCRC and non-CRC were enrolled. Treatment patterns, overall survival (OS) from the start of third-line (3L, for mCRC) or second-line (2L, for non-CRC) treatment, and the best overall response rate (BORR) were reported. Results Thirty-six patients with dMMR/MSI-H mCRC were included. Almost all patients received combination treatments both in first-line (1L, 100%) and 2L (97%). For 3L and later, combination treatment was preferred over monotherapy but decreased in usage (75% at 3L and 57% at fourth-line, 4L). The BORR was 5.7% and median OS for patients with dMMR/MSI-H mCRC receiving 3L therapy was 9.0 months (95% confidence interval, CI 4.0–14.1); it decreased to 4.1 months (95% CI 4.0–9.0) when survival data of patients receiving ICIs at fourth or later lines were censored at progression date of prior treatment line. Conclusion Real-world clinical outcomes observed for patients with dMMR/MSI-H mCRC receiving 3L treatment(s) are suboptimal, suggesting a high unmet need that could be addressed with ICIs.