As shown in Table 2, substantial heterogeneities were found among all studies for the MnSOD Val16Ala polymorphism and overall cancer risk (homozygous: P < 0.001; heterozygous: P = 0.001; recessive: P < 0.001; dominant: P < 0.001; and allele comparison: P < 0.001). The gene discussed is SOD2; the disease is cancer.