Correlation between the EGFR intron 1 CA dinucleotide repeat and skin toxicity in lung cancer patients treated with erlotinib

Abstract

14001 Background: Acneiform rash is the main toxicity of erlotinib, an epidermal growth factor receptor (EGFR) inhibitor. The length of the CA dinucleotide repeat in EGFR intron 1 has been suggested to predict the biological effects of tyrosin kinase inhibitors. Thus, we compared this polymorphism with the rash severity in non-small cell lung cancer (NSCLC) patients treated with erlotinib. Methods: Toxicity was evaluated in 18 metastatic or locally advanced unresectable NSCLC patients treated orally with 150 mg/d of erlotinib: 7 retrospectively and 11 prospectively. Rash was graded according to a modified scale based on the Common Toxicity Criteria v.3.0, which subclassified grade II rash into IIA (topic intervention indicated) and IIB (oral intervention indicated). Genomic DNA was isolated from each patient; the length of the EGFR intron 1 CA dinucleotide repeat was measured by PCR amplification and analyzed on a capillary sequencer. Results: The most common EGFR genotypes were: 16, 20, 17 and 18 CA repeats (with 50, 25, 8 and 8% frequency, respectively). 33% of the subjects with a total amount of CA repeats <34 had grade IIB-III rash vs 11% of the subjects with =34 CA repeats. In addition, all patients with 0 grade toxicity belonged to the =34 CA group. When the only patient with a previous dermatological disease (psoriasis) was excluded from the analysis, the difference between both groups increased, reaching statistical significance (p=0.047). Conclusions: This data suggests that NSCLC patients with long EGFR intron 1 CA alleles present lower grades of skin toxicity when treated with erlotinib than patients with short CA alleles. Further studies are required to confirm this data. [Table: see text] No significant financial relationships to disclose.