[A Case of Advanced Recurrent Rectal Cancer Successfully Treated by Rechallenge Therapy with an Anti-Epidermal Growth Factor Receptor(EGFR)Drug].

The patient was a 75-year-old man who had undergone potentially curative surgery for Stage Ⅲb rectal cancer followed by resection of liver metastases. Two years after the resection of liver metastases, lung and remnant liver metastases were found. He received chemotherapy for unresectable metastatic tumors. Based on the findings of molecular and pathological examinations(RAS: wild type; BRAF: wild type; MSI: negative; HER2: negative), the following chemotherapy regimens were administered: first-line, FOLFIRI plus panitumumab(PANI); second-line, mFOLFOX6; third-line, trifluridine/tipiracil; fourth- line, regorafenib. After fourth-line treatment, he was judged to have disease progression due to the increase in his lung and liver metastases and the elevation of tumor markers. All standard regimens were refractory, but the Eastern Cooperative Oncology Group performance status was zero and a liquid biopsy for RAS still showed wild type. Therefore, rechallenge therapy with anti-epidermal growth factor receptor(EGFR)drugs, cetuximab(CET)and irinotecan(IRI), was administered 13 months after the final course of FOLFIRI plus PANI treatment. After 4 courses of CET plus IRI, the size of the 2 metastatic tumors markedly decreased and his tumor marker levels normalized.