A Promising Combination Therapy of Sintilimab and Regorafenib for Microsatellite Stable Advanced Colorectal Cancer: A Case Report

Immune checkpoint inhibitors (ICIs) have significantly impacted the treatment landscape for colorectal cancer (CRC), particularly in mismatch repair-deficient or microsatellite instability-high (MSI-H/dMMR) cases. However, as only a small percentage of metastatic CRC cases fall into this category, patients with microsatellite stability or mismatch repair proficiency (MSS/pMMR) face limited treatment options due to low response rates to ICI monotherapy. While combination therapies of immunotherapy and targeted treatment have shown promise in MSS CRC cases, the existing data remains inconclusive and necessitates further exploration through real-world clinical cases and large-scale studies. This case report details the journey of a 52-year-old male patient with MSS CRC and peritoneal and left supraclavicular lymph node metastasis. Starting with cetuximab and FOLFOX as first-line treatments, followed by bevacizumab plus FOLFIRI as second-line, the patient eventually received third-line therapy comprising regorafenib and sintilimab, yielding complete remission of the primary lesion and peritoneal metastases after four treatment cycles. A subsequent PET/CT scan showed reduced tumor activity in the left supraclavicular lymph nodes, prompting radiotherapy and continued sintilimab administration for two years, resulting in no tumor recurrence or metastasis post-treatment completion. This case highlights the efficacy and safety of combining sintilimab and regorafenib in rapidly progressing MSS CRC cases, offering a promising treatment strategy. It underscores the importance of exploring effective biomarkers and treatment modalities for MSS CRC to tailor therapies and enhance patient outcomes in the future. Further research and clinical trials are essential to validate these findings and optimize treatment approaches for CRC patients.