A 70-year-old man had radical surgery for colon cancer one year before the symptoms of memory loss and decreasing cognitive function. Subsequent magnetic resonance imaging revealed a brain mass, which was surgically resected and confirmed to be metastatic intestinal adenocarcinoma. Immunohistochemistry of the primary tumor and brain metastasis showed mismatch repair deficiency. The patient received adjuvant chemotherapy after surgery. However, the brain metastasis relapsed one month after the last chemotherapy. Genetic testing on the resected colon tumor samples confirmed microsatellite instability-high with a high tumor mutation burden by 77.7 muts/Mb. The patient was subsequently treated with programmed death-1 (PD-1) monoclonal antibody pembrolizumab (keytruda). The brain metastatic lesions were completely shrunk, and a complete clinical response was achieved.
一例70岁男性患者，在接受右半肠癌根治性手术1年后出现了记忆丧失和认知功能下降的症状，头颅磁共振成像检查发现脑部肿块，手术后经病理检查确诊为结肠腺癌转移。原发灶及颅内转移瘤免疫组织化学检测均提示为错配修复缺陷。原发结肠肿瘤组织基因检测证实为微卫星高度不稳定伴有高肿瘤突变负荷，肿瘤突变负荷为77.7 muts/Mb。患者结肠癌根治术和颅内转移瘤术后均接受了辅助化疗，但在颅内转移瘤切除术和化疗结束后1个月颅内转移复发。患者接受帕博利珠单抗治疗后结果颅内转移瘤消退并达到临床完全缓解。.
Keywords: Brain metastasis; Case report; Colorectal cancer; High tumor mutation burden; Microsatellite instability-high; Programmed death-1 monoclonal antibody.