Hormonal factors and pancreatic cancer risk in women: The Malmö Diet and Cancer Study.

The incidence of pancreatic cancer is leveling between sexes. Smoking, high age and heredity are established risk factors, but evidence regarding the influence of hormonal factors is unclear. In this study, we investigated the associations of reproductive factors, use of oral contraceptives (OC) and hormone replacement therapy (HRT) with pancreatic cancer risk in the Malmö Diet and Cancer Study, a prospective, population-based cohort encompassing 17,035 women. Up until 31 December 2015, 110 women were identified with incident pancreatic cancer through the Swedish Cancer Registry. Higher age at menarche was significantly associated with pancreatic cancer risk (age-adjusted [hazard ratio] HR = 1.17; 95% confidence interval [CI] 1.04-1.32, and fully adjusted HR = 1.17; 95% CI 1.04-1.32). Ever use of OC was not significantly associated with pancreatic cancer risk but ever use of HRT was significantly associated with a decreased risk of pancreatic cancer (age-adjusted HR = 0.47, 95% CI 0.23-0.97, and fully adjusted HR = 0.48, 95% CI 0.23-1.00), in particular use of estrogen-only regimen (age-adjusted HR = 0.21; 95% CI 0.05-0.87 and fully adjusted HR = 0.22; 95% CI 0.05-0.90). Age at menopause or first childbirth, parity and breastfeeding history were not significantly associated with pancreatic cancer risk. Collectively, these findings suggest a protective role of female hormones against pancreatic cancer. Further studies are needed, and potential modifying genetic factors and indirect hazardous effects of smoking should also be considered.