A Case of MSI-H Ascending Colon Cancer which Achieved a Pathological CR after Pembrolizumab Administration

Abstract

An 82-year-old man underwent ileo-transverse colon anastomosis for cT4b (ureter, iliopsoas) N1bM0 cStage IIIc ascending colon cancer. Postoperatively, the patient was started on CapeOX+Bev as systemic chemotherapy, and the efficacy was judged to be SD. Pathology on the biopsy specimen confirmed MSI-High status, so systemic therapy was switched to pembrolizumab. After 6 courses of pembrolizumab, a CT scan showed that the tumor had shrunk, and the ureteral invasion had disappeared. In the hope of achieving a complete elimination, we then performed a right hemicolectomy and D3 lymph node dissection. Histologically, no residual tumor cells were found in the specimen, and the patient was pathologically CR. No signs of recurrence or metastasis have been observed during one year of ongoing follow-up visits.