[A Case of Rectal Cancer with Unresectable Liver Metastasis Responding to Rechallenge with FOLFIRI].

A 63-year-old man underwent low anterior resection for rectal cancer.A synchronous liver metastasis located in segment 8 was 12 cm in diameter and unresectable due to its proximity to the inferior vena cava(IVC).The postoperative pathological findings revealed a T3(SS), N0, M1(liver)Stage IV tumor, and wild type K-RAS was expressed.We chose FOLFIRI plus cetuximab(Cmab)for first-line chemotherapy.After 6 courses, we changed the molecular target drug from Cmab to bevacizumab( Bmab)because the liver metastasis remained unresectable.The patient had long-term stable disease(SD)for approximately 30 months with the FOLFIRI-based regimen.We then changed the regimen to mFOLFOX6 plus Bmab for second-line, Cmab for third-line, and trifluridine/tipiracil hydrochloride for fourth-line chemotherapy to treat progressive disease(PD).After treatment with these chemotherapies, the patient wished to continue treatment.We restarted FOLFIRI plus Bmab for fifth-line chemotherapy as his general condition was still good.Consequently, his tumor markers levels decreased with stabilization of the disease on CT scans, and he continued therapy for 6 months while maintaining a good quality of life.This case suggested that rechallenge with anti-cancer agents could be effective and improve the prognosis of colorectal cancer patients after using all key drugs.