Table 2.
The oral contraceptive “univariate” association between aspects of oral contraceptive use and risk of ovarian cancer for 3989 BRCA1 and 2445 BRCA2 mutation carriers
| Variable |
BRCA1 mutation carriers |
BRCA2 mutation carriers |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| OvCa+, n (%)c | OvCa−, n (%)c | Weighted,a,b HR (95% CI)d | OvCa+, n (%)c | OvCa−, n (%)c | Weighted,a,b HR (95% CI)e | |||||
| Oral contraceptive use | ||||||||||
| Never (<6 mo) | 133 | (41.4) | 659 | (19.1) | 1.00 | 46 | (46.5) | 426 | (19.3) | 1.00 |
| Ever | 188 | (58.6) | 2788 | (88.9) | 0.51 (0.36–0.71) | 53 | (53.5) | 1782 | (80.7) | 0.65 (0.35–1.19) |
| Ever, starting age unknown | 11 | 125 | 4 | 87 | ||||||
| Missing | 14 | 71 | 3 | 44 | ||||||
| Calendar year at start | ||||||||||
| Never (<6 mo) | 133 | (41.4) | 659 | (19.1) | 1.00 | 46 | (46.5) | 426 | (19.3) | 1.00 |
| ≤1975 | 114 | (35.5) | 684 | (19.8) | 0.45 (0.33–0.62) | 39 | (39.4) | 492 | (22.3) | 0.73 (0.38–1.39) |
| >1975 | 74 | (23.1) | 2104 | (61.0) | 0.56 (0.35–0.88) | 14 | (14.1) | 1290 | (58.4) | 0.49 (0.23–1.05) |
| Ever, starting year unknown | 11 | 125 | 4 | 87 | ||||||
| Missing | 14 | 71 | 3 | 44 | ||||||
| Total duration of use | ||||||||||
| Never (<6 mo) | 133 | (43.0) | 659 | (20.2) | 1.00 | 46 | (47.4) | 426 | (20.4) | 1.00 |
| <5 y | 67 | (21.7) | 616 | (18.9) | 0.79 (0.53–1.19) | 17 | (17.5) | 401 | (19.2) | 0.87 (0.42–1.80) |
| 5–9 y | 53 | (17.2) | 867 | (26.6) | 0.54 (0.35–0.85) | 13 | (13.4) | 557 | (26.6) | 0.51 (0.23–1.12) |
| ≥10 y | 56 | (18.2) | 1121 | (34.4) | 0.32 (0.21–0.50) | 21 | (21.7) | 707 | (33.8) | 0.60 (0.28–1.27) |
| Ever, no period specific data | 23 | 309 | 6 | 204 | ||||||
| Missing | 14 | 71 | 3 | 44 | ||||||
| Trendf | P=2.0E-04 | P=.449 | ||||||||
| Time since last use | ||||||||||
| Never (<6 mo) | 133 | (43.0) | 659 | (20.2) | 1.00 | 46 | (47.4) | 426 | (20.4) | 1.00 |
| <10 y | 29 | (9.4) | 1478 | (45.3) | 0.40 (0.22–0.71) | 7 | (7.2) | 825 | (39.5) | 0.36 (0.14–0.92) |
| 10–19 y | 60 | (19.4) | 648 | (19.9) | 0.54 (0.36–0.82) | 12 | (12.4) | 415 | (19.9) | 0.58 (0.24–1.42) |
| ≥20 y | 87 | (28.2) | 478 | (14.7) | 0.61 (0.43–0.87) | 32 | (33.0) | 425 | (20.3) | 0.78 (0.40–1.52) |
| Ever, no period specific data | 23 | 309 | 6 | 204 | ||||||
| Missing | 14 | 71 | 3 | 44 | ||||||
| Trendf | P=.025 | P=.258 | ||||||||
| Starting age | ||||||||||
| Never (<6 mo) | 133 | (41.4) | 659 | (19.1) | 1.00 | 46 | (46.5) | 426 | (19.3) | 1.00 |
| ≤19 y | 62 | (19.3) | 1753 | (50.9) | 0.43 (0.28–0.65) | 20 | (20.2) | 1030 | (46.7) | 1.02 (0.43–2.42) |
| 20–23 y | 58 | (18.1) | 615 | (17.8) | 0.51 (0.33–0.78) | 12 | (12.1) | 461 | (20.9) | 0.49 (0.20–1.23) |
| >23 y | 68 | (21.2) | 420 | (12.2) | 0.63 (0.41–0.97) | 21 | (21.2) | 291 | (13.2) | 0.60 (0.29–1.21) |
| Ever, starting age unknown | 11 | 125 | 4 | 87 | ||||||
| Missing | 14 | 71 | 3 | 44 | ||||||
| Trendf | P=.154 | P=.114 | ||||||||
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.
Weighted: to account for the oversampling of affected individuals (breast and ovarian cancer)
Unweighted results: never or ever use: BRCA1 HR, 0.72; 95 CI%, 0.58–0.90; BRCA2 HR, 0.80; 95 CI%, 0.55–1.17. In both unweighted and weighted analyses, the same characteristics of oral contraceptive use were significantly associated
Distribution of variables at end of follow-up
Intrinsically stratified on study (EMBRACE, GENEPSO, other) and birth cohort (1920–1946, 1947–1954, 1955–1980). Clustered on family membership
Intrinsically stratified on study (EMBRACE, other incl GENEPSO) and birth cohort (1920–1943, 1944–1980). Clustered on family membership
Trend tests were based on the P value of the category-specific mean as a continuous variable of ever oral contraceptive users.