SIRT6 and osteosarcoma: Multivariable analyses showed tumor size (OS; P = 0.023, RFS; P = 0.018), distant metastasis (OS; P = 0.008, RFS; P = 0.050), and SIRT6 expression (OS; P = 0.001, RFS; P < 0.001) as independent prognostic indicators of osteosarcoma patients (Table 3).