Table 3.
The associations of duration, recency, and starting use of oral contraceptives and risk of ovarian cancer for BRCA1 mutation carriers
| Variable | OvCa+, n (%)a | OvCa−, n (%)a | Oral contraceptive univariate,b,c HR (95% CI) | Oral contraceptive multivariate,b,c,d HR (95% CI) | ||
|---|---|---|---|---|---|---|
| Mutually adjusted | ||||||
| Oral contraceptive never use | 133 | (43.0) | 659 | (20.2) | 1.15 (0.40–3.34) | |
| Total duration of use, y | ||||||
| <5 | 67 | (21.7) | 616 | (18.9) | 1.00 | 1.00 |
| 5–9 | 53 | (17.2) | 867 | (26.6) | 0.69 (0.43–1.09) | 0.67 (0.40–1.12) |
| ≥10 | 56 | (18.2) | 1121 | (34.4) | 0.40 (0.25–0.65) | 0.37 (0.19–0.73) |
| Trende | P=2.0E-04 | P=.008 | ||||
| Time since last use, y | ||||||
| <10 | 29 | (9.4) | 1478 | (45.3) | 1.00 | 1.00 |
| 10–19 | 60 | (19.4) | 648 | (19.9) | 1.35 (0.77–2.37) | 0.96 (0.50–1.83) |
| ≥20 | 87 | (28.2) | 478 | (14.7) | 1.50 (0.85–2.66) | 0.79 (0.35–1.78) |
| Trende | P=.015 | P=.238 | ||||
| Starting age, y | ||||||
| ≤19 | 58 | (18.8) | 1632 | (50.0) | 1.00 | 1.00 |
| 20–23 | 51 | (16.5) | 580 | (17.8) | 1.07 (0.68–1.70) | 0.98 (0.61–1.58) |
| >23 | 67 | (21.7) | 392 | (12.0) | 1.51 (0.91–2.50) | 1.15 (0.65–2.04) |
| Trende | P=.154 | P=.665 | ||||
| Ever, starting age unknown | 23 | 309 | ||||
| Missing | 14 | 71 | ||||
| Stratified for recency of use | HR (95% CI)c | |||||
| Total duration of use | ||||||
| Never (<6 mo) | 133 | (43.0) | 659 | (20.2) | 1.00 | |
| <15 y since last use | ||||||
| <5 y | 10 | (3.2) | 288 | (8.8) | 1.21 (0.55–2.68) | |
| 5–9 y | 16 | (5.2) | 580 | (17.8) | 0.61 (0.30–1.24) | |
| ≥10 y | 25 | (8.1) | 956 | (29.3) | 0.24 (0.14–0.43) | |
| Trendc | P=2.2e-04 | |||||
| >15 y since last use | ||||||
| <5 y | 57 | (18.5) | 328 | (10.1) | 0.72 (0.48–1.07) | |
| 5–9 y | 37 | (12.0) | 287 | (8.8) | 0.47 (0.29–0.76) | |
| ≥10 y | 31 | (10.0) | 165 | (5.1) | 0.56 (0.18–0.59) | |
| Trendc | P=.374 | |||||
| Ever, no period specific data | 23 | 309 | ||||
| Missing | 14 | 71 | ||||
BRCA, breast cancer gene; CI, confidence interval; EMBRACE, Epidemiological Study of Familial Breast Cancer; GENEPSO, Gene Etude Prospective Sein Ovaire; HR, hazard ratio; OvCa, ovarian cancer.
Schrijver et al. Oral contraceptive use and ovarian cancer risk for BRCA1/2 mutation carriers. Am J Obstet Gynecol 2021.
Distribution of variables at end of follow-up
Weighted: to account for the oversampling of affected individuals (breast and ovarian cancer)
Intrinsically stratified on study (EMBRACE, GENEPSO, other) and birth cohort (1920–1946, 1947–1954, 1955–1980). Clustered on family membership
In addition: mutually adjusted for duration, time since, and age at start of oral contraceptive use
Trend tests were based on the P value of the category-specific mean as a continuous variable of ever oral contraceptive users.