Pubertal Timing and Incident Ovarian Cancer in the Sister Study Cohort.

Background: Pubertal milestones such as menarche (first period) and thelarche (onset of breast development) are markers of hormonal changes that may be relevant to the hormonal etiology of ovarian cancer. Prior studies of the association between age at menarche and ovarian cancer risk have been inconsistent, whereas age at thelarche has not been examined in relation to ovarian cancer incidence.

Methods: With data from 40,809 women in the Sister Study, we used multivariable-adjusted Cox proportional hazards regression to estimate HRs and 95% confidence intervals (CI) for associations of self-reported ages at thelarche and menarche with incident ovarian cancer, both overall and by histotype.

Results: During a median follow-up of 13.3 years, 291 women reported a diagnosis of ovarian cancer. Ages at thelarche (HR = 0.94; 95% CI, 0.87-1.02 per 1-year older) and menarche (HR = 0.99; 95% CI, 0.91-1.07 per 1-year older) were not associated with ovarian cancer overall. Although imprecise, HRs suggested a possible inverse association of ages at thelarche (HR = 0.71; 95% CI, 0.48-1.04) and menarche (HR = 0.79; 95% CI, 0.59-1.04) with the incidence of clear-cell tumors.

Conclusions: Ages at thelarche and menarche were not associated with ovarian cancer incidence overall.

Impact: Though our results do not provide clear evidence of associations of pubertal timing with ovarian cancer incidence, possible associations of earlier thelarche and menarche with increased incidence of ovarian clear-cell carcinoma may warrant further investigation, especially considering secular trends toward earlier thelarche.