Table 4.
Clinicopathological features and primary resistance to T-DM1
| Characteristics | No. of patients (%) | p value |
|---|---|---|
| All patients | 34 | |
| Primary resistance to T-DM1 | 9 (26.5) | |
| De novo stage IV or recurrent | 1 | |
| De novo stage IV | 9 | |
| Primary resistance to T-DM1 | 2 (22.2) | |
| Recurrent | 25 | |
| Primary resistance to T-DM1 | 7 (28.0) | |
| Hormone receptor status | 0.438 | |
| ER and/or PR positive | 17 | |
| Primary resistance to T-DM1 | 6 (35.3) | |
| ER and PR negative | 17 | |
| Primary resistance to T-DM1 | 3 (17.6) | |
| T-DM1 as second-line therapy or earlier | 17 | 0.438 |
| Primary resistance to T-DM1 | 3 (17.6) | |
| T-DM1 as later than second-line therapy | 17 | |
| Primary resistance to T-DM1 | 6 (35.3) | |
| Prior anthracycline | 1 | |
| Yes | 11 | |
| Primary resistance to T-DM1 | 3 (27.3) | |
| No | 23 | |
| Primary resistance to T-DM1 | 6 (26.1) | |
| Prior pertuzumab | 0.462 | |
| Yes | 15 | |
| Primary resistance to T-DM1 | 5 (33.3) | |
| No | 19 | |
| Primary resistance to T-DM1 | 4 (21.1) | |
| Prior lapatinib | 1 | |
| Yes | 11 | |
| Primary resistance to T-DM1 | 3 (27.3) | |
| No | 23 | |
| Primary resistance to T-DM1 | 6 (26.1) | |
| HER2 gene amplification in ctDNA | 0.245 | |
| Positive | 5 | |
| Primary resistance to T-DM1 | 0 (0) | |
| Negative | 11 | |
| Primary resistance to T-DM1 | 4 (36.4) | |
| PIK3CA mutation in ctDNA | 0.05 | |
| Mutation positive | 2 | |
| Primary resistance to T-DM1 | 2 (100) | |
| Mutation negative | 14 | |
| Primary resistance to T-DM1 | 2 (14.3) |