Oral contraceptive and reproductive risk factors for ovarian cancer within sisters in the breast cancer family registry
Ferris, J.S.; Daly, M.B.; Buys, S.S.; Genkinger, J.M.; Liao, Y.; Terry, M.B.
British Journal of Cancer 110(4): 1074-1080
2014
ISSN/ISBN: 0007-0920 PMID: 24398512 DOI: 10.1038/bjc.2013.803Document Number: 581083
Oral contraceptive use has been consistently associated with a reduced risk of ovarian cancer in unrelated, average risk women; however little data exist on whether this benefit extends to higher risk women from cancer families. To examine this, we conducted family-based analyses using the Breast Cancer Family Registry. We used generalised estimating equations to obtain the population average effect across all families (n=389 cases, n=5643 controls) and conditional logistic regression to examine within-family differences in a subset with at least two sisters discordant on ovarian cancer status (n=109 cases, n=149 unaffected sister controls). In the multivariable generalised estimating equation model there was a reduced risk of ovarian cancer for ever use of oral contraceptives compared with never use (OR=0.58, 95% CI: 0.37, 0.91), and in the conditional logistic model there was a similar inverse association; however, it was not statistically significant (OR=0.52, 95% CI: 0.23, 1.17). We examined this association by BRCA1/2 status and observed a statistically significant reduced risk in the non-carriers only. We observed a decreased risk of ovarian cancer with oral contraceptive use supporting that this association observed in unrelated women extends to related women at higher risk.