Table 2.
Hazard ratio (HR) estimates for breast cancer risk in SLE, with 95% confidence intervals
| Variables* | Univariate HR | Non-stratified Adjusted** | Stratified Adjusted** |
|---|---|---|---|
| Calendar year | 1.01 (0.98, 1.03) | 0.99 (0.95, 1.04) | 1.05 (0.98, 1.13) |
| Age(years) | 1.05 (1.03, 1.07) | 1.05 (1.03, 1.07) | 1.06 (1.03, 1.08) |
| White race/ethnicity | 1.92 (1.08, 3.41) | 1.54 (0.78, 3.04) | 1.45 (0.58, 3.63) |
| Ever smoking | 1.59 (0.94, 2.69) | 1.21 (0.66, 2.22) | 1.36 (0.66, 2.80) |
| dsDNA antibody positivity | 0.80 (0.40, 1.60) | 0.93 (0.36, 2.37) | 0.86 (0.27, 2.74) |
| Steroids ever | 1.08 (0.64, 1.81) | 1.90 (0.85, 4.26) | 2.66 (0.97, 7.32) |
| Cumulative Steroids ≥3.5 grams (gm) | 0.80 (0.49, 1.29) | 0.65 (0.32, 1.32) | 0.54 (0.24, 1.25) |
| Cyclophosphamide ever | 0.77 (0.35, 1.70) | 0.79 (0.19, 3.31) | 0.85 (0.17, 4.36) |
| Cumulative cyclophosphamide ≥6 gm. | 0.74 (0.28, 1.94) | 1.61 (0.29, 9.02) | 1.29 (0.14, 11.6) |
| Azathioprine ever | 0.62 (0.37, 1.06) | 0.62 (0.19, 1.96) | 0.77 (0.17, 3.51) |
| Cumulative azathioprine > 3.65 gm | 0.50 (0.26, 0.94) | 0.96 (0.29, 3.22) | 0.83 (0.17, 3.94) |
| Methotrexate ever | 1.56 (0.83, 2.94) | 1.88 (0.90, 3.94) | 1.79 (0.68, 4.71) |
| Mycophenolate ever | 0.47 (0.11, 1.94) | 0.59 (0.14, 2.55) | 0.34 (0.04, 2.84) |
| Non-steroidal drugs ever | 1.53 (0.94, 2.50) | 1.51 (0.82, 2.77) | 1.97 (0.63, 6.19) |
| Antimalarial drugs ever | 1.08 (0.66, 1.76) | 0.64 (0.28, 1.45) | 0.72 (0.21, 2.48) |
| Antimalarial drugs > 5 years | 1.37 (0.83, 2.24) | 1.44 (0.69, 3.02) | 1.24 (0.42, 3.67) |
| Activity top quartile*** | 0.73 (0.40, 1.33) | 0.82 (0.39, 1.75) | 0.61 (0.22, 1.74) |
| Number of pregnancies | 1.03 (0.87, 1.21) | 0.96 (0.83, 1.12) | 0.97 (0.83, 1.13) |
| Menopause | 2.22 (1.21, 4.05) | 1.09 (0.51, 2.33) | 0.98 (0.34, 2.78) |
| Hormone replacement ever | 2.17 (1.07, 4.41) | 1.11 (0.49, 2.52) | 1.43 (0.58, 3.52) |
| Oral contraceptive ever | 1.82 (0.88, 3.77) | 1.81 (0.74, 4.41) | 2.03 (0.56, 7.39) |
| Family history breast cancer | 2.68 (1.15, 6.24) | 2.12 (0.85, 5.29) | 1.34 (0.50, 3.60) |
*
Drug and disease activity variables were time-dependent up to the event-time for each risk set. dsDNA antibody positivity is a weighted average of the number of times positive over time
**
One multivariate model stratified by centre, the other did not; both multivariate models adjusted for all variables listed in the model.
***
Assessed by Systemic Lupus Erythematosus Disease Activity Index-2K scores; at one centre (San Francisco), disease activity was captured only with self-report items.