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.

Abstract

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.

Results: A total of 112 patients received gefitinib therapy, 74 patients received erlotinib therapy, and 17 patients received erlotinib and gefitinib sequentially. The OR of developing rash with gefitinib versus erlotinib treatment was 0.38 (95% confidence interval [CI], 0.15-0.86). The OR of developing diarrhea with gefitinib versus erlotinib treatment was 0.46 (95% CI, 0.22-0.94). The OR of developing liver dysfunction with gefitinib versus erlotinib treatment was 3.30 (95% CI, 1.59-7.22). Reduced function of CYP2D6 was not associated with an increased risk of any adverse events in both gefitinib and erlotinib cohorts.

Conclusions: Erlotinib had higher rate of rash and diarrhea than gefitinib. Liver dysfunction occurred significantly more often in the gefitinib group than in the erlotinib group.