| Classification | HR (95% CI) | p-value |
| All patients | ||
| Paesmans et al. [4] | 8.23 (5.88–11.69) | <0.001 |
| Sculier et al. [2] | 9.46 (6.67–13.50) | <0.001 |
| Patients with extensive disease | ||
| Paesmans et al. [4] | 5.60 (3.13–9.93) | <0.001 |
| Sculier et al. [2] | 12.49 (5.57–28.01) | <0.001 |
| Foster et al. [7] | 8.83 (4.66–16.74) | <0.001 |
Hazard ratios (HRs) are for a continuous covariate calculated as a linear combination of the independent prognostic covariates weighted by their regression coefficients.