factors have been associated with ovarian cancer, the strongest being
parity and oral contraceptive use. Given reductions in birth rates and
increases in oral contraceptive use over time, associations in more
recent birth cohorts may differ. Furthermore, consideration of ovarian
cancer heterogeneity (i.e., Type I/II invasive cancers) may contribute
to a better understanding of etiology. We examined hormone-related
factors in relation to ovarian cancer risk overall, for Type I and Type
II cancers, as well as borderline tumors.
population-based case–control study was carried out in Montreal, Canada
from 2011 to 2016, including 496 cases and 908 controls. For each
hormone-related variable, adjusted odds ratios (OR) and 95% confidence
intervals (CI) were estimated using logistic regression for ovarian
cancer overall, and using polytomous logistic regression for
associations by tumor behavior and ovarian cancer type.
was inversely associated with risk overall and by tumor behavior and
type, with a stronger OR for Type I for ≥3
full-term births vs. nulliparity] vs. Type II invasive cancers; the OR for borderline tumors was 0.41. Oral contraceptive ever use was not associated with risk
overall, but ≥10 years of use vs. never use reduced risk, particularly
for invasive cancers. A history of endometriosis was most strongly
associated with Type I cancers. Associations with other factors were
results suggest that associations with some hormone-related factors may
differ between borderline and invasive Type I and II ovarian cancers.