Table 2 Subgroup analyses for overall survival
Stratified | No. of studies | I2 (%) | HR (95% CI) | P value |
|---|---|---|---|---|
Publication date (year) | ||||
 1990–2000 | 4 | 0 | 0.17 (0, 0.34) | 0.049 |
 2001–2010 | 7 | 4.5 | 0.32 (0.19, 0.45) | < 0.0001 |
 2011–2018 | 14 | 74.7 | 0.37 (0.25, 0.48) | < 0.0001 |
Study size (no. of patients) | ||||
 < 500 | 9 | 63.1 | 0.42 (0.12, 0.71) | 0.005 |
 ≥ 500 | 5 | 63.1 | 0.32 (0.23, 0.40) | < 0.0001 |
Region | ||||
 Asia | 4 | 0 | 0.31 (0.17, 0.45) | < 0.0001 |
 Europe | 12 | 56.9 | 0.29 (0.12, 0.46) | 0.0001 |
 America | 5 | 88.7 | 0.40 (0.22, 0.57) | < 0.0001 |
 Australia | 3 | 0 | 0.29 (0.14, 0.44) | < 0.0001 |
Surgical type | ||||
 Colorectal | 18 | 48.6 | 0.31 (0.21, 0.41) | < 0.0001 |
 Colonic | 4 | 59.8 | 0.37 (0.23, 0.52) | < 0.0001 |
 Rectal | 2 | 63.8 | 0.28(− 0.21, − 0.77) | 0.258 |