Presentation Information
[ICS-2]Treatment Strategy for Colorectal Cancer with Deficient Mismatch Repair
Kenji Fujiyoshi, Takahiro Shigaki, Naohiro Yoshida, Takafumi Ohchi, Takefumi Yoshida, Fumihiko Fujita (Depertment of Surgery, Kurume University)
The carcinogenesis of colorectal cancer (CRC) is classified into microsatellite instability (MSI) and chromosomal instability pathways. Deficient mismatch repair (dMMR)/MSI-high (MSI-H) status, identified by MSI or immunohistochemistry (IHC) testing, is a key biomarker, as these tumors show high response rates to immune checkpoint inhibitors (ICIs). Consequently, treatment strategies for dMMR/MSI-H CRC differ significantly from those for pMMR/MSS tumors.
Current standards of care include pembrolizumab for advanced disease and CAPOX/FOLFOX as adjuvant therapy for Stage III tumors, given their resistance to 5-FU. Recently, neoadjuvant therapy with ipilimumab plus nivolumab has demonstrated remarkably high pathological response rates in resectable dMMR colon cancer, heralding a paradigm shift.
Reflecting these advances, our institution now performs routine upfront MMR-IHC testing to guide treatment. We present the case of a 29-year-old male with dMMR rectal cancer who was enrolled in a clinical trial. He achieved a clinical complete response (cCR) with immunotherapy, successfully avoided surgery, and returned to work.
The evolution of treatment for dMMR CRC has made non-operative management (NOM) following neoadjuvant ICI a viable option. This progress underscores the critical need for upfront molecular evaluation, positioning MMR status assessment as a top priority to facilitate personalized, organ-sparing strategies.
Current standards of care include pembrolizumab for advanced disease and CAPOX/FOLFOX as adjuvant therapy for Stage III tumors, given their resistance to 5-FU. Recently, neoadjuvant therapy with ipilimumab plus nivolumab has demonstrated remarkably high pathological response rates in resectable dMMR colon cancer, heralding a paradigm shift.
Reflecting these advances, our institution now performs routine upfront MMR-IHC testing to guide treatment. We present the case of a 29-year-old male with dMMR rectal cancer who was enrolled in a clinical trial. He achieved a clinical complete response (cCR) with immunotherapy, successfully avoided surgery, and returned to work.
The evolution of treatment for dMMR CRC has made non-operative management (NOM) following neoadjuvant ICI a viable option. This progress underscores the critical need for upfront molecular evaluation, positioning MMR status assessment as a top priority to facilitate personalized, organ-sparing strategies.