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Successful Treatment of Locally Advanced Microsatellite Instability-High Ascending Colon Cancer Using an Immune
Taiki Nabekura1, Yu Sato1, Nobuyuki Hiruta2
1Department of Surgery, Toho University Sakura Medical Center, Sakura, Chiba, Japan.
Surgical Case Reports
|May 1, 2025
Summary
Neoadjuvant immunotherapy with pembrolizumab significantly shrank unresectable, advanced colon cancer in a microsatellite instability-high patient. This approach enabled less invasive surgery and achieved complete tumor disappearance, showcasing immunotherapy
Area of Science:
- Oncology
- Gastroenterology
- Immunotherapy
Background:
- Colorectal cancer (CRC) management requires personalized approaches, including targeted therapies and immune checkpoint inhibitors (ICIs).
- While ICIs are approved for advanced/recurrent CRC in Japan, their preoperative use remains unestablished.
- Neoadjuvant immunotherapy shows promise for immunogenic CRCs (microsatellite instability-high [MSI-H]/deficient mismatch repair [dMMR]).
Observation:
- A 70-year-old male with unresectable, locally advanced, MSI-H ascending colon cancer received neoadjuvant chemotherapy with pembrolizumab.
- The patient experienced adverse events, including diarrhea and pruritus, suspected to be immune-related.
- Significant tumor shrinkage was observed via CT scan approximately 6 months after treatment initiation.
Findings:
- The MSI-H and BRAF-mutated tumor responded robustly to neoadjuvant pembrolizumab, facilitating standard surgery.
- The patient underwent surgery without adjunct organ resection, and the perioperative course was uneventful.
- Pathological examination revealed complete tumor disappearance (histological effect of chemotherapy: Grade 3).
Implications:
- This case demonstrates the potential of neoadjuvant immunotherapy to reduce surgical invasiveness in colorectal cancer.
- Preoperative ICI therapy may offer a viable strategy for managing locally advanced, immunogenic CRC.
- Further research is warranted to explore the efficacy and safety of neoadjuvant immunotherapy in CRC.
