Stratification analysis of the combined genotypes of the <i>PTEN</i>, <i>AKT1</i>, <i>MDM2</i> and <i>p53</i> polymorphisms and risk of nasopharyngeal carcinoma.

Abbreviations: OR, odds ratio; CI, confidence interval. aORs and P values were calculated by multivariate logistic regression, adjusted for age, sex, smoking and drinking status, smoking level and nationality when appropriate within the strata. bFor differences in ORs within each stratum. cLow-risk group, individuals carrying 0–2 risk genotypes; high-risk group, individuals carrying 3–4 risk genotypes.