“…Nine [ 9 , 17 – 22 , 24 , 25 ], nine [ 9 , 17 – 22 , 24 , 25 ], seven [ 9 , 17 , 18 , 20 – 22 , 25 ], six [ 9 , 18 , 20 , 21 , 23 , 25 ] studies reported 1-, 2-, 3-, 5- year survival rates, respectively. There were no significant differences in the 1- and 2-year survival rates between the two study groups (1-year survival rate: RR, 0.81; 95 % CI, 0.60 to 1.09; P = 0.17, Additional file 2 A; 2-year survival rate: RR, 0.90; 95 % CI, 0.77 to 1.04; P = 0.15, Additional file 2 B).…”