TAC1 and oral cavity cancer: Site-specific DFS time did not differ significantly in patients with methylated versus unmethylated genes, with two notable exceptions: it was significantly shorter when SST was unmethylated in laryngeal cancer (log-rank test, P = 0.001) and when TAC1 was methylated in oral cavity cancer (log-rank test, P = 0.001) (Additional file 5: Figure S3, Additional file 6: Figure S4, Additional file 7: Figure S5, and Additional file 8: Figure S6).