Use of EGF A61G polymorphism to predict overall survival in a phase III study of gemcitabine plus cetuximab versus gemcitabine in patients with locally advanced or metastatic pancreatic adenocarcinoma (SWOG 0205).

Abstract

203 Background: The SWOG 0205 phase III study failed to demonstrate an advantage from the addition of cetuximab to gemcitabine for overall survival (OS), progression-free survival (PFS) or objective response in advanced pancreatic cancer. Molecular markers may identify subgroups of pts who benefit from this regimen. This report summarizes the results of a pilot project aimed at screening germline single nucleotide polymorphisms (SNPs) in genes involved in gemcitabine metabolism pathway (CDA and RRM1) and EGFR signaling pathway (EGF, EGFR, IGF1, FCGR2A/3A, KRAS, IL8, COX-2, CCND1) to identify pts that may benefit from this treatment. Methods: Genomic DNA was extracted from 88 available serum samples for this molecular correlates pilot study. Sixteen SNPs were evaluated using PCR-based protocols. There were no differences in baseline characteristics or outcome between pts included in the analysis and the entire study population. Associations between genotype and OS were assessed using stratified Cox regression, with adjustment for treatment arm. Genotypes were parameterized as the number of dominant alleles. No p value adjustments were made for multiple comparisons. Results: Median age was 63.3 years (range: 29.6-85.0), and median OS (95% CI) was 5.7 months (mos) (range: 4.4-6.8) in this subset. There was a statistically significant association between EGF A61G SNP (rs4444903) genotype and OS (p=0.04). Among pts carrying the AA genotype, median OS was 8.4 mos (95% CI 4.9-15.0), as compared to 5.6 mos (95% CI 3.0-9.0) among those with the AG genotype and 5.3 mos. (95% CI 2.2-7.1) for the GG genotype. Evidence was weak for interaction between treatment arm and rs4444903 genotype (p=0.13). No significant associations between other SNPs and OS were observed. Conclusions: This exploratory study suggests that the EGF A61G polymorphism may be a useful molecular marker for predicting clinical outcomes in metastatic pancreatic adenocarcinoma pts treated with gemcitabine-based chemotherapy.