Reproductive factors, exogenous hormone use, and risk of pancreatic cancer in postmenopausal women.

Introduction: The epidemiologic literature on menstrual and reproductive factors associated with pancreatic cancer has yielded weak and inconsistent evidence of an association. Furthermore, few cohort studies have examined the association of exogenous hormone use, including type and duration, with this disease. The aim of this study was to assess the association of these exposures with risk of pancreatic cancer in a large cohort of postmenopausal women.

Methods: We used data from the Women's Health Initiative on 1003 cases of pancreatic cancer diagnosed among 158,298 participants over 14.3 years of follow-up. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for the associations of interest.

Results: Being parous vs. nulliparous was associated with reduced risk (HR=0.84, 95% CI 0.70-1.00), and women who had 1-2 and 3-4 births were at decreased risk compared to nulliparous women, whereas women who had >5 births showed no decrease in risk. Compared to women who gave birth between the ages of 20-29, women who gave birth at age 30 or above were at increased risk (HR 1.23, 95% CI 1.00-1.53, p for trend 0.003). Other reproductive factors and exogenous hormone use were not associated with risk.

Conclusions: Together with the existing literature on this topic, our results suggest that reproductive and hormonal exposures are unlikely to play an important role in the etiology of pancreatic cancer.