Reproductive Factors, Use of Exogenous Hormones, and Pancreatic Cancer Incidence: The Norwegian Women and Cancer Study

Abstract

Introduction The incidence of pancreatic cancer is increasing worldwide and characterized by a particularly low survival rate. Studies have reported weak and inconsistent evidence for associations among reproductive factors, use of exogenous hormones, and pancreatic cancer incidence in women. Purpose To investigate relationships between reproductive factors, exogenous hormones, and the rate of pancreatic cancer incidence in a large population-based prospective cohort of women in Norway. Methods We used data from the Norwegian Women and Cancer study on 588 incident cases of pancreatic cancer diagnosed among 165,419 women, with mean follow-up of 18.7 years. Cox proportional-hazard models were used to estimate HRs and 95% CIs for associations of interest. Results Cumulative breastfeeding duration >24 months was associated with 63% decreased incidence of pancreatic cancer compared to no breastfeeding. We observed an inverse linear dose–response trend between cumulative breastfeeding duration and pancreatic cancer incidence, which was confirmed in parous women and ever-smokers. Higher age at first birth and menopause were inversely associated with pancreatic cancer incidence, though with less precise effect estimates. Current use of oral contraceptives was associated with a doubling of pancreatic cancer incidence, but the analysis was hampered by a small number of cases. There was no evidence of any associations between age at menarche, parity or use of menopausal hormone therapy, and incidence of pancreatic cancer. Conclusion Our results suggest a potential protective effect of breastfeeding duration against pancreatic cancer incidence. Inconsistent results for the other reproductive factors suggested no important role of estrogens in pancreatic cancer etiology.

The Disproportionate Rise in Pancreatic Cancer in Younger Women Is Due to a Rise in Adenocarcinoma and Not Neuroendocrine Tumors: A Nationwide Time-Trend Analysis Using 2001–2018 United States Cancer Statistics Databases

“…Research on the association between reproductive factors and the risk of PDAC has shown heterogenous results. Some studies have suggested that high parity [ 17 , 18 ], having had two children [ 19 ], and a cumulative breastfeeding duration of over 24 months [ 20 ] are associated with a decreased risk of pancreatic cancer. However, subsequent large cohort studies [ 21 , 22 ] have failed to identify a strong association between reproductive factors and pancreatic cancer risk.…”

Adherence to the 2018 World Cancer Research Fund (WCRF)/American Institute for Cancer Research (AICR) Cancer Prevention Recommendations and risk of 14 lifestyle-related cancers in the UK Biobank prospective cohort study

“…The importance of breastfeeding in influencing pancreatic cancer risk is uncertain. The Norwegian Women and Cancer study reported an inverse linear relationship between cumulative breastfeeding duration and pancreatic cancer incidence [ 26 ], although no significant associations were found in a study in Japan [ 27 ].…”

The causal relationships between early sexual behaviors and cancer risks in individuals of European ancestry: a two-step Mendelian randomization study

“…Many observational studies investigated the association between age at rst birth and breast cancer risk [11,12], but these results are inconsistent. Moreover, meta-analysis shows age at rst birth was associated with lung cancer risk, pancreatic cancer risk [13,14], and has no signi cant association with liver cancer [15]. Nevertheless, some of the results are inexact and the underlying mechanism needs further investigation.…”