| Classification | Group I | Group II | Group III | Group IV | Group V | Missing |
| All patients# | ||||||
| Albain et al. [5] | 145 (21) | 60 (9) | 227 (33) | 178 (26) | 83 | |
| Sagman et al. [6] | 212 (31) | 37 (5) | 364 (53) | 73 (11) | 7 | |
| Paesmans et al. [4] | 113 (17) | 352 (53) | 103 (15) | 98 (15) | 27 | |
| Sculier et al. [2] | 195 (28) | 53 (8) | 279 (40) | 166 (24) | ||
| Patients with extensive disease¶ | ||||||
| Albain et al. [5] | 227 (56) | 178 (44) | 50 | |||
| Sagman et al. [6] | 23 (5) | 356 (79) | 73 (16) | 3 | ||
| Paesmans et al. [4] | 227 (53) | 103 (24) | 98 (23) | 27 | ||
| Sculier et al. [2] | 10 (2) | 279 (61) | 166 (37) | |||
| Foster et al. [7] | 232 (51) | 34 (7) | 131 (29) | 4 (1) | 52 (12) | 2 |
Data are presented as n (%) or n. #: n = 693; ¶: n = 455.