High Prevalence of EGFR R479K (rs2227983) Polymorphism in Indian Head and Neck Cancer Patients: Association with Unfavourable Clinical Outcome

Objective: The Epidermal Growth Factor Receptor (EGFR) gene, is host to several single nucleotide polymorphisms (SNPs), R497K (rs2227983) is one such example. The current study was conducted to screen a cohort of Indian Head and Neck Squamous Cell Carcinoma patients (HNSCC), for R497K variant of EGFR gene and to correlate effect of the SNP on survival parameters of the cohort. Method: Tumour samples were collected from 50 HNSCC patients from Apollo Hospital, Chennai. Genomic DNA from the samples was then extracted by using the high-salt method. The extracted DNA was then screened for EGFR R497K SNP by polymerase chain reaction coupled with restriction fragment length polymorphism (PCR-RFLP) technique. The PCR-RFLP results were then re-confirmed by Sanger sequencing. Then Kaplan-Meier statistical analysis was used to corelate between the SNP data to the survival rates (overall survival (OS) and progression free survival (PFS) of our patients. Results: Our study found, That among 50 patients 84% (42/50) in the cohort carried this SNP (78% were heterozygous, and 6% were homozygous), and only 16% (8/50) were wild type. Median OS for homozygous, heterozygous and wild type variant were 30.8 months (SE ±3.302; 95% CI: 24.39–37.36), 34.7 months (SE ±2.152; 95% CI: 30.51–38.94), and 41.4 months (SE ±0.511; 95% CI: 39.96–42.37), respectively with p-value of 0.409. Similarly, median PFS for homozygous, heterozygous and wild type variant were 30.0 months (SE ±3.952; 95% CI: 13.08–47.09), 33.5 months (SE ±2.404; 95% CI: 28.66–38.39), and 40.4 months (SE ±1.162; 95% CI: 39.49–41.44) respectively, with 0.553 p-value. Though it is not statistically significant, our study reports a declining trend in the OS and PFS of patients carrying the R497K polymorphism compared to the wild type patients. Conclusion: The SNP R497K of EGFR gene has high prevalence in our Indian study population, which corelates with poor prognosis for HNSCC.