One mutant allele in IL-18 G-137C polymorphism increased the chance of cancer (OR = 5.583, 95% CI = 3.04–10.22, P < 0.001) and two mutant alleles increased more (OR = 9.571, 95% CI = 3.10–29.46, P < 0.001). The gene discussed is IL18; the disease is cancer.