The overall results suggested there was a significant association between MnSOD Val16Ala polymorphism and cancer risk (homozygous: OR = 1.09, 95% CI = 1.00–1.19, P < 0.001; heterozygous: OR = 1.07, 95% CI = 1.02–1.12, P = 0.001; dominant: OR = 1.08, 95% CI = 1.02–1.14, P < 0.001; and allele comparison: OR = 1.06, 95% CI = 1.02–1.11, P < 0.001) (Table 2, Figure 2). Here, SOD2 is linked to cancer.