MGMT and carcinoma: For 13 genes reported in at least three studies between HBV-positive carcinoma tissues and HBV-negative carcinoma tissues (Table 1), no evidence of statistical heterogeneity was observed for 12 genes, including p16 (I2 = 49%), RASSF1A (I2 = 46%), GSTP1 (I2 = 0%), APC (I2 = 0%), RUNX3 (I2 = 0%), p14 (I2 = 39%), WIF1 (I2 = 0%), PRDM2 (I2 = 15%), p15 (I2 = 0%), SOCS1 (I2 = 8%), SFRP1 (I2 = 0%) and MGMT (I2 = 0%).