Table 4.
Factors associated with membership in the bottom quintile of endoxifen concentration
| N | % in Endoxifen Bottom Quintile | Chi-sq | p | |
|---|---|---|---|---|
| BMI | ||||
| <25 | 597 | 15.9 | 15.9 | 0.001 |
| 25 –29.9 | 429 | 21.2 | ||
| 30–34.9 | 199 | 22.6 | ||
| 35+ | 145 | 29.7 | ||
| CYP2D6 phenotype | ||||
| UM | 27 | 7.4 | 242.5 | <0.001 |
| EM | 1097 | 12.9 | ||
| IM | 164 | 41.5 | ||
| PM | 82 | 75.6 | ||
| Race/ethnicity | ||||
| White | 1191 | 21.2 | 12.04 | 0.017 |
| Hispanic | 68 | 7.4 | ||
| African-American | 31 | 22.6 | ||
| Asian/PI | 57 | 12.3 | ||
| Other | 23 | 8.7 | ||
| Age | ||||
| <45 | 137 | 17.5 | 3.00 | 0.22 |
| 45–54 | 548 | 22.3 | ||
| 55+ | 685 | 18.7 | ||
| Tamoxifen quintile | ||||
| Q 1 (low) | 274 | 39.8 | 108.6 | <0.001 |
| Q 2 | 273 | 23.7 | ||
| Q 3 | 279 | 16.1 | ||
| Q 4 | 269 | 13.5 | ||
| Q 5 (high) | 275 | 6.9 | ||
| Tamoxifen duration at time of blood draw | ||||
| ≤12 mos. | 581 | 19.4 | 2.43 | 0.489 |
| 13–24 mos | 432 | 22.0 | ||
| 25–36 mos | 266 | 19.5 | ||
| >36 mos | 91 | 15.4 | ||
Abbreviations: UM, Ultra-rapid Metabolizer; EM, Extensive Metabolizer; IM, Intermediate Metabolizer; PM, Poor Metabolizer