Background/Aim: Combination chemotherapies of oxaliplatin or irinotecan with fluoropyrimidine and molecular target drug were reported to be active in several clinical studies and so regarded as a first-line standard therapy for unresectable or metastatic colorectal cancer. However, the incidence of adverse events is not so low. We investigated the efficacy and safety of chemotherapy combined bevacizumab with fluoropyrimidine as a first-line treatment for frail patients. Methods: Twenty-six patients with unresectable or metastatic colorectal cancer who were treated with first-line chemotherapy combined bevacizumab with S-1 or 5FU/LV (modified Roswell Park Memorial Institute regimen) at our hospital between October 2007 and December 2010 were retrospectively investigated. Results: The median age was 72 years (range 66-84). Performance status was 0, 1 and 2 in 8, 17 and 1 patient, respectively. The primary lesion was located in the colon in 14 patients and in the rectum in 12. Twenty patients were with resection of the primary lesion and 6 were without, 8 were with postoperative adjuvant chemotherapy and 18 were without. The number of metastasized organs was 1, 2 and 3 in 17, 9 and 0 patients, respectively. The liver, lung, lymph node and peritoneum were metastasized in 9, 9, 11 and 5 patients, respectively. The KRAS gene was wild in 11, mutated in 7 and unknown in 8 patients. Bevacizumab with S-1 was used in 17 patients and bevacizumab with 5FU/LV was used in 9. Response and disease control rates were 50 and 100%, respectively. The median duration of progression-free survival was 9.1 months and the median time to treatment failure was 9.0 months. The incidences of all grades of neutropenia and hypertension were 31%, those of grade 3 or severer were 12%, and those of other adverse events were low. Grade 3 cerebral hemorrhage, grade 4 pulmonary embolism and grade 5 febrile neutropenia each occurred in 1 patient. Conclusion:The first-line chemotherapy combined bevacizumab with fluoropyrimidine for frail patients with unresectable or metastatic colorectal cancer in Japan was comparable to the safety and efficacy of combination therapy reported previously in Western countries. Copyright (C) 2013 S. Karger AG, Basel