Table 2.
Characteristics of the patients with stage IV lung cancer harboring uncommon mutation receiving a first-line tyrosine kinase inhibitor (TKI), classified by the exon of epidermal growth factor receptor (EGFR) mutation.
| Mutation Only in exon 18 | Mutation Only in exon 20 | Mutation Only in exon 21 | Mutations in Multiple Exons | p Value * | |
|---|---|---|---|---|---|
| n | 21 (37%) | 16 (28%) | 13 (23%) | 7 (12%) | |
| Age (year), mean ± SD | 66 ± 13 | 63 ± 10 | 69 ± 13 | 64 ± 11 | 0.6964 |
| Age (year), median (IQR) | 64 (55–79) | 65 (55–70) | 67 (56–78) | 63 (60–73) | 0.6964 |
| Age (year), n (%) | 0.7749 | ||||
| <65 | 11 (52%) | 9 (56%) | 6 (46%) | 5 (71%) | |
| ≥65 | 10 (48%) | 7 (44%) | 7 (54%) | 2 (29%) | |
| Sex, n (%) | 1.0000 | ||||
| Female | 12 (57%) | 9 (56%) | 7 (54%) | 4 (57%) | |
| Male | 9 (43%) | 7 (44%) | 6 (46%) | 3 (43%) | |
| Smoking history, n (%) | 0.3188 | ||||
| Never | 14 (67%) | 11 (69%) | 8 (62%) | 7 (100%) | |
| Current | 7 (33%) | 5 (31%) | 5 (38%) | 0 (0%) | |
| Performance status, n (%) | 0.0799 | ||||
| ECOG 0–1 | 17 (81%) | 7 (44%) | 9 (69%) | 6 (86%) | |
| ECOG 2–4 | 4 (19%) | 9 (56%) | 4 (31%) | 1 (14%) | |
| No. of metastatic sites, n (%) | 0.3715 | ||||
| =1 | 11 (52%) | 7 (44%) | 4 (31%) | 5 (71%) | |
| ≥2 | 10 (48%) | 9 (56%) | 9 (69%) | 2 (29%) | |
| Metastatic site, n (%) | |||||
| Brain | 5 (24%) | 5 (31%) | 3 (23%) | 1 (14%) | 0.8976 |
| Leptomeningeal | 0 (0%) | 2 (13%) | 0 (0%) | 0 (0%) | 0.2644 |
| Lung | 4 (19%) | 5 (31%) | 9 (69%) | 2 (29%) | 0.0288 |
| Bone | 11 (52%) | 8 (50%) | 9 (69%) | 2 (29%) | 0.3946 |
| Pleural | 11 (52%) | 8 (50%) | 7 (54%) | 3 (43%) | 1.0000 |
| Pericardial | 3 (14%) | 0 (0%) | 1 (8%) | 1 (14%) | 0.4222 |
| Liver | 1 (5%) | 2 (13%) | 6 (46%) | 0 (0%) | 0.0109 |
| Adrenal | 3 (14%) | 2 (13%) | 0 (0%) | 0 (0%) | 0.5324 |
| TKI medication, n (%) | 0.2374 | ||||
| Afatinib | 4 (19%) | 8 (50%) | 2 (15%) | 3 (43%) | |
| Gefitinib | 14 (67%) | 7 (44%) | 7 (54%) | 3 (43%) | |
| Erlotinib | 3 (14%) | 1 (6%) | 4 (31%) | 1 (14%) | |
| Initial response to TKI, n (%) | 0.0212 | ||||
| Partial response | 8 (38%) | 1 (6%) | 5 (38%) | 5 (71%) | |
| Stable disease | 10 (48%) | 6 (38%) | 5 (38%) | 1 (14%) | |
| Progressive disease | 3 (14%) | 9 (56%) | 3 (23%) | 1 (14%) | |
| Response rate to TKI | 8 (38%) | 1 (6%) | 5 (38%) | 5 (71%) | 0.0118 |
| Disease control rate with TKI | 18 (86%) | 7 (44%) | 10 (77%) | 6 (86%) | 0.0357 |
| Median PFS on TKI (month) | 9.2 | 2.8 | 9.0 | 13.5 | 0.1592 |
| Median OS (month) | 20.0 | 14.7 | 17.0 | 20.5 | 0.6596 |
* Kruskal-Wallis test or Fisher’s exact test or Log-rank test.