Effective Treatment of Chemotherapy with Anti-EGFR Antibody for an Unresectable Lynch Syndrome-associated Small Intestinal Cancer—A Case Report—

Abstract

A 67-year-old man was undergoing postoperative follow-up for two colorectal cancers. Laparoscopic partial resection of the small intestine and excisional biopsy of the mesenteric lymph node of the small intestine were performed after neoplastic lesions of the small intestine with distant lymph node metastasis were diagnosed by CT and FDG-PET in August 2017. The pathological diagnosis was primary small intestinal cancer with lymph node metastases. After the operation, chemotherapy with anti-EGFR antibody was started for the remaining mesenteric lymph node and distant lymph node metastases, and the distant lymph nodes shrank, resulting in a complete response. Screening for Lynch syndrome was performed, and a germline gene examination showed a pathogenic variant in the MSH2 gene, which was diagnosed as Lynch syndrome. Systemic chemotherapy was then continued, and the complete response was maintained. However, the treatment was discontinued in December 2018 at the patient's request. In February 2019, the patient was diagnosed with bladder cancer and chemotherapy for it was started, but the bladder cancer was refractory to it. In July of the same year, treatment with pembrolizumab was started at our hospital. The bladder cancer progressed, and the patient finally died a year later.