Complete remission of peritoneal dissemination of colon cancer by alternate-day S-1 and oxaliplatin plus bevacizumab treatment and maintenance chemotherapy comprising alternate-day S-1 plus bevacizumab: A case report

A 56-year-old man diagnosed with sigmoid colon cancer underwent sigmoid colectomy. Nine months later, his serum carcinoembryonic antigen (CEA) level had increased, and the diagnosis of recurrent peritoneal dissemination was made based on positron emission tomography/computed tomography (PET/CT) findings. Although systemic chemotherapy comprising S-1 and oxaliplatin (SOX) plus bevacizumab was initiated, severe diarrhea occurred on day 4 of the second cycle despite reduction in S-1 dose. By changing the daily oral intake schedule for S-1 to an alternate-day intake from the third cycle (modified SOX plus bevacizumab), the patient was able to continue undergoing chemotherapy without any adverse gastrointestinal effects. All tumors disappeared after four cycles, and the patients received eight cycles of modified SOX plus bevacizumab followed by maintenance chemotherapy comprising alternate-day S-1 plus bevacizumab. Maintenance chemotherapy was discontinued after 17 cycles owing to adverse events, including thrombocytopenia, corneal and lacrimal duct disorders, and hyperbilirubinemia. The patient has been radiographically confirmed to be in remission for 5 years without any recurrence, and his serum CEA level has been within normal range for >3 years. To conclude, compared with the conventional consecutive treatment, alternate-day SOX plus bevacizumab treatment may reduce the adverse effects of these chemotherapeutic drugs.