Table 2. ESR1 mutant allele frequency in serial blood draws from positive cfDNA samples.
| Patient ID | Months After Start of Palbociclib and Letrozole | ESR1-D538G | ESR1-Y537N | ESR1-Y537S |
|---|---|---|---|---|
| CF6 | ||||
| Draw 1 | 1.4 | 1.12 ± 0.04 | ND | ND |
| Draw 2 | 14.0 | 9.90 ± 1.18 | ND | ND |
| Draw 3 | 15.3 | 11.23 ± 0.29 | ND | ND |
| CF8 | ||||
| Draw 1 | 1.8 | ND | ND | ND |
| Draw 2 | 2.3 | ND | ND | ND |
| Draw 3 | 3.2 | 1.07 ± 0.08 | ND | ND |
| Draw 4 | 4.1 | 1.54 ± 0.10 | ND | ND |
| CF14 | ||||
| Draw 1 | 2.5 | ND | ND | 3.26 ± 0.19 |
| CF15 | ||||
| Draw 1 | 2.8 | 0.35 ± 0.02 | ND | 2.18 ± 0.05 |
| Draw 2 | 4.6 | 4.12 ± 0.07 | 0.91 ± 0.05 | 5.37 ± 0.03 |
| CF16 | ||||
| Draw 1 | 2.8 | ND | ND | ND |
| Draw 2 | 3.8 | ND | 0.12 ± 0.01 | ND |
| Draw 3 | 13.1 | ND | ND | ND |
| Draw 4 | 14.5 | ND | ND | ND |
Average mutant allele frequency ± SEM is indicated using data from at least three replicates (after subtraction of background noise). LLoD of 0.1% was used as cut-off. ND represents mutation not detected.