Comparison of Adverse Events of Erlotinib with those of Gefitinib in Patients with Non-small Cell Lung Cancer : A Case-control Study in a Japanese Population

Background : Rash, liver dysfunction, and diarrhea are known as adverse events of erlotinib and gefitinib. However, clinical trials with gefitinib have reported different adverse events compared to those with erlotinib. In an in vitro study, cytochrome P450 (CYP) 2D6 was shown to be involved in the metabolism of gefitinib and not of erlotinib. It has been hypothesized that gefitinib therapy results in different adverse events compared to erlotinib therapy. / Methods : The frequency of each adverse event was evaluated in a case-control study on Japanese patients who were treated with gefitinib or erlotinib. The CYP2D6 phenotype was categorized into 2 groups according to functional or reduced metabolic levels. In addition, we evaluated the odds ratio (OR) of adverse events with each factor, including CYP2D6 activities as well as treatment types....