Abstract
B94
Adult body mass index (BMI) has been positively associated with ovarian cancer risk in some studies, but few studies have examined the role of body size during earlier periods of life. Therefore, we prospectively examined associations of body shape at ages 5 and 10, BMI at age 18, height, and birthweight with risk of epithelial ovarian cancer among participants in the Nurses’ Health Study (NHS) and Nurses’ Health Study II (NHS II). Ovarian cancer risk factors were assessed on biennial mailed questionnaires, beginning in 1976 and 1989 for the NHS and NHS II, respectively. Women recalled their body shapes at ages 5 and 10 using a validated nine-level somatotype pictogram. Height was reported at baseline and was used with recalled weight at age 18 to calculate BMI at age 18. Birthweight was recalled in categories. Incident cases of ovarian cancer during follow-up - through June 1, 2004 for the NHS and June 1, 2005 for the NHS II - were confirmed by review of pathology reports. Analyses included up to 110,311 women and 735 ovarian cancer cases in the NHS and 113,059 women and 138 cases in the NHS II. Cox proportional hazards regression was used to estimate relative risks (RRs) and 95% confidence intervals (CIs), adjusting for established ovarian cancer risk factors. Average body shape at ages 5 and 10 was inversely associated with ovarian cancer risk in the NHS (RR for most overweight compared to most lean = 0.81, 95% CI = 0.53-1.24, P trend = 0.04) and positively associated with risk in the NHS II (comparable RR = 2.09, 95% CI = 0.97-4.47, P trend = 0.10) (P for heterogeneity = 0.01). Combining both cohorts and stratifying by menopausal status, greater body shape at ages 5 and 10 was associated with reduced risk in postmenopausal women (RR for most overweight compared to most lean = 0.84, 95% CI = 0.54-1.31) and increased risk in premenopausal women (comparable RR = 1.38, 95% CI = 0.70-2.71), although neither of these trends was statistically significant. Greater BMI at age 18 was not significantly associated with risk in premenopausal or postmenopausal women. Height was positively associated with risk in both cohorts (pooled RR for ≥ 1.75 meters compared to < 1.6 meters = 1.43, 95% CI = 1.05-1.96, P trend = 0.001), although the association appeared to be stronger in the NHS II (comparable RR = 2.35, 95% CI = 1.19-4.62). Birthweight was not associated with risk of ovarian cancer in either cohort. These results suggest that body size in early life may be related to ovarian cancer risk and that the associations may differ by menopausal status. Further research should examine the biologic mechanisms that might explain the observed associations.
Sixth AACR International Conference on Frontiers in Cancer Prevention Research-- Dec 5-8, 2007; Philadelphia, PA