Objective: Previously, we suggested that oxaliplatin (L-OHP)-related grade 3/4 hypersensitivity reactions occurred immediately after the initiation, but grade 1/2 reactions did not. This study was conducted to clarify the risk factors for L-OHP-related hypersensitivity reactions.Methods: Clinical data from 108 Japanese patients with colorectal cancer were analyzed, who were treated with L-OHP-containing regimens, FOLFOX4 and/or mFOLFOX6. The risk factors examined included demographic data, preexisting allergies, laboratory test data, treatment regimen, treatment line of therapy, pretreatment with steroids, total number of cycles and cumulative amount of L-OHP.Results: The incidence of grade 1/2 and grade 3/4 hypersensitivity reactions were found at 13.0% (14/108) and 9.3% (10/108), respectively. Female (P=0.037), preexisting allergies (P=0.004) and lower level of lactate dehydrogenase (P=0.003) were risk factors for grade 1/2 hypersensitivity reactions, and higher neutrophil count (P=0.043) and lower monocyte count (P=0.007) were for grade 3/4 reactions. Total number of cycles were larger in the patients with grade 3/4 reactions than those without reactions (P=0.049).Conclusions: Further extensive examination with a large number of patients is needed to establish a patient management strategy.

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