| MPE | Wild-type | Del-19 | L858R | Others | Total |
| At initial diagnosis | 116 (31.8) | 97 (26.6) | 119 (32.6) | 33 (9.0) | 365 |
| Following disease progression | 36 (43.4) | 21 (25.3) | 15 (18.1) | 11 (13.3) | 83 |
| Total | 152 (33.9) | 117 (26.1) | 134 (29.9) | 45 (10.0) | 448 |
Data are presented as n (%) or n. Each patient is included only once. No patients had different EGFR mutations in several malignant pleural effusion (MPE) samples, except acquired T790M EGFR mutation. Del-19: deletion in exon 19. MPEs at initial diagnosis versus MPEs after disease progression for wild-type and EGFR mutations, p=0.044. MPEs at initial diagnosis versus MPEs after disease progression for different mutation status, p=0.033. MPEs at initial diagnosis versus MPEs after disease progression for L858R versus non-L858R (including wild-type, Del-19 and other types), p=0.009.