Table 4.
Estrogen plus progestin and breast cancer risk by quartiles of baseline sex hormones
| Sex hormone | Odds ratio (95% confidence interval)* | P interaction† |
|---|---|---|
| Total estradiol, pg/mL | .04 | |
| Quartile (Q)1(2.5–7.94) | 2.47 (1.28 to 4.79) | |
| Q2 (7.95–10.89) | 1.34 (0.68 to 2.65) | |
| Q3 (10.90–14.99) | 1.73 (0.85 to 3.51) | |
| Q4 (15.00–39.20) | 0.96 (0.44 to 2.09) | |
| Bioavailable estradiol, pg/mL | .02 | |
| Q1 (1.58–4.99) | 2.35 (1.20 to 4.64) | |
| Q2 (5.00–7.14) | 1.58 (0.80 to 3.11) | |
| Q3 (7.15 – 10.52) | 1.98 (0.96 to 4.05) | |
| Q4 (10.53–29.30) | 0.75 (0.34 to 1.64) | |
| Estrone, pg/mL | .02 | |
| Q1 (9.05–27.86) | 3.06 (1.52 to 6.17) | |
| Q2 (27.87–36.78) | 1.12 (0.56 to 2.23) | |
| Q3 (36.79–50.38) | 1.95 (0.96 to 3.97) | |
| Q4 (50.39–151.39) | 0.95 (0.45 to 2.03) |
* Adjusted for age at menarche, body mass index, and family history for breast cancer. Odds ratios compare estrogen plus progestin treatment to placebo in each hormone quartile. Results were obtained using conditional logistic regression models. All statistical tests were two-sided.
† P value for interaction between hormone therapy and sex hormone level (continuous scale).