Correlation of plasma erlotinib trough concentration with skin rash in Chinese NSCLC patients harboring exon 19 deletion mutation.

Purpose: Erlotinib is an essential drug for non-small cell lung cancer (NSCLC) patients harboring epidermal growth factor receptor (EGFR) activating mutations. The relationship between the pharmacokinetics and skin rash and diarrhea of erlotinib in Chinese patients with EGFR mutated NSCLC is unknown. In this study, we evaluated the variability in erlotinib trough concentration and its relationship with the severity of skin rash and diarrhea in patients with two common types of EGFR mutations: a deletion in exon 19 and point mutations in exon 21 L858R.

Patients And Methods: EGFR mutation-positive Chinese patients (n = 52) treated with erlotinib were included in our study; the steady-state trough concentrations were assessed; and the occurrence and severity of skin rash and diarrhea after the onset of treatment with erlotinib were recorded. The patients were divided into two groups by mutation type (exon 19 deletions or exon 21 L858R point mutations). Occurrence and severity of skin rash and diarrhea was analyzed in both groups.

Results: The overall mean (± SD) steady-state trough concentration for erlotinib was 1380 ± 663 ng/mL, and there was no significant difference of erlotinib concentrations between the two mutation groups. Occurrence and severity of skin rash was significantly associated with trough concentration in patients with exon 19 deletions but not exon 21 L858R point mutations. Significant association of erlotinib concentrations with diarrhea was found neither in the exon 19 deletions group nor in the exon 21 L858R point mutation group.

Conclusions: The occurrence and severity of skin rash correlated with increase in erlotinib trough concentrations only in Chinese patients with exon 19 deletion; the erlotinib trough concentrations were not associated with diarrhea.