Impact of omitting fluorouracil from FOLFIRI plus bevacizumab as second-line chemotherapy for patients with metastatic colorectal cancer

Purpose Fluorouracil, leucovorin, and irinotecan (FOLFIRI) plus bevacizumab is the standard second-line chemotherapy for patients with metastatic colorectal cancer (mCRC) who are refractory or intolerant to fluoropyrimidines and oxaliplatin. However, the benefits of incorporating fluoropyrimidines into second-line chemotherapy for patients with mCRC who are refractory to fluoropyrimidines are unknown. Methods We retrospectively evaluated patients with mCRC who were administered irinotecan plus bevacizumab or FOLFIRI plus bevacizumab as second-line chemotherapy at a single institution from January 2010 to April 2020. We compared the efficacy and safety of irinotecan plus bevacizumab (IRI group) with those of FOLFIRI plus bevacizumab (FOLFIRI group). Results Of the 255 enrolled patients, 107 (IRI/FOLFIRI group, 31/76 patients) were eligible for analysis. After a median follow-up of 13.1 months (range 1.2-48.4) and 14.3 months (range 0.9-46.5) for the IRI and FOLFIRI groups, respectively, the median progression-free survival was 6.4 months and 5.8 months [adjusted hazard ratio (aHR), 0.82; 95% confidence interval (CI) 0.50-1.34, p = 0.44] and the median overall survival was 16.6 months and 16.5 months (aHR, 1.01; 95% CI 0.59-1.69; p = 0.97) in the IRI and FOLFIRI groups, respectively. All-grade nausea, stomatitis, neutropenia, thrombocytopenia, Grade 3/4 neutropenia, and febrile neutropenia occurred more frequently in the FOLFIRI group than in the IRI group. Conclusion Our study suggests omitting fluorouracil from FOLFIRI plus bevacizumab as the second-line chemotherapy decreases adverse events without affecting the treatment efficacy in patients with mCRC who are refractory to fluoropyrimidines. Further randomized prospective studies are warranted to validate our result.