MSH3 and MSH6 gene polymorphisms: Association with lung cancer susceptibility and prognostic value in patients with NSCLC undergoing platinum-based chemotherapy

9031 Background: DNA mismatch repair (MMR) pathway is responsible for recognizing and repairing errors (insertion, deletion and misincorporation of bases) occurring during DNA replication and recombination. Single nucleotide polymorphisms (SNPs) in MSH3 and MSH6 genes are related to development of various cancers. SNPs of particular interest include rs26279 G > A polymorphism for MSH3 and rs3136228 557G > T polymorphism for MSH6. In this cohort study, we evaluated the association of MSH3 (rs26279) and MSH6 (rs3136228) SNPs with occurrence of lung cancer (LC), baseline demographic and clinical characteristics and with overall survival (OS) amongst LC patients undergoing platinum-based doublet chemotherapy. Methods: 500 LC patients and 500 healthy controls were enrolled. Genomic DNA was isolated from 4ml of peripheral blood using a phenol-chloroform extraction procedure and genotyping of patients and controls was performed using PCR-RFLP. All enrolled patients had pathologically confirmed LC. Written informed consent was obtained from all enrolled subjects and the study was approved by institutional ethics committee. Odds ratio (OR) and 95% confidence intervals (CIs) were calculated using logistic regression analysis. Kaplan-Meier method was used for OS analysis and (multivariate) Cox regression models to obtain (adjusted) hazards ratios (HRs). Results: Mean age (61 years) was similar for cases and controls. Compared to controls, LC cohort had higher prevalence of non-smokers (20% vs. 10%), female sex (20% vs. 9%) and smoking pack-years (mean 20.8 vs. 13.8). Majority of LC patients had metastatic disease (54%) and ECOG performance status of 0-1 (45%) or 2 (40%). Adenocarcinoma and squamous were equi-prevalent (41% each). Mutant genotype (TT) for MSH6 polymorphism was more frequent in LC patients (OR = 1.43; 95% CI = 1.01 – 2.03; p = 0.03) with the association more marked in adenocarcinoma histology (OR = 1.74; 95% CI = 1.05 – 2.93; p = 0.03). For non-smokers, mutant genotype (TT) for MSH6 polymorphism was associated with a 3-fold increased risk of LC (OR = 3.22; 95% CI = 1.26 – 8.18; p = 0.01). Amongst females, heterozygous genotype (GA) for MSH3 polymorphism was more frequent amongst LC cases (24%) than controls (16%) (OR = 2.35, 95% CI = 0.85 – 6.52, p = 0.04). Patients treated with docetaxel-platinum chemotherapy and carrying heterozygous (GT) genotype for MSH6 polymorphism had worse OS (median 4.9 vs 9.1 months; adjusted HR = 2.3; p = 0.03). No association was observed between MSH3 (rs26279) and MSH6 (rs3136228) polymorphisms and other baseline clinical/demographic characteristics. Conclusions: The results of this cohort study suggest that MSH3 and MSH6 polymorphisms are involved in modulating the risk towards LC occurence. MSH6 polymorphism is also associated with higher mortality amongst patients treated with docetaxel-platinum chemotherapy.