The phase III West Japan Oncology Group (WJOG) 4407G study showed noninferiority of folinic acid, bolus/continuous fluorouracil, and irinotecan plus bevacizumab to modified folinic acid, bolus/continuous fluorouracil, and oxaliplatin 6 plus bevacizumab in progression-free survival (PFS) as first-line chemotherapy for patients with metastatic colorectal cancer. The aim of this study was to evaluate the predictive and prognostic value of morphologic response in patients with colorectal liver metastases (CLM) as a post hoc analysis of the WJOG4407G study.Morphologic response was assessed by comparing contrast-enhanced computed tomography (CT) images at baseline and week 8. Three blinded radiologists evaluated CT images and classified their response as optimal, incomplete, or no response according to the morphologic criteria. Response evaluation criteria in solid tumors (RECIST) response, early tumor shrinkage (ETS), and depth of response (DpR) were also evaluated.Among 395 patients who were eligible for efficacy analysis in the WJOG4407G study, 70 patients had liver-limited disease. We finally evaluated 55 of these patients. Optimal morphologic response was identified in 19 of 55 patients (34.5%). The median PFS was 10.7 months for patients with optimal response and 10.1 months in those with incomplete/no response (log-rank, P = .96). The median overall survival (OS) was 26.2 and 35.5 months, respectively (log-rank, P = .062). According to univariate analysis, morphologic response was not associated with PFS or OS, whereas RECIST response was significantly associated with both PFS and OS, with ETS and DpR being associated with significantly longer PFS.Morphologic response might be neither a predictive nor a prognostic factor in patients with CLM undergoing chemotherapy containing bevacizumab, whereas RECIST response was significantly associated with both PFS and OS.
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