Medications, sex hormones and reproductive factors in relation to gastro-oesophageal cancer risk and survival

This thesis did not show any evidence that HRT was associated with worse survival in patients with gastro-oesophageal cancer.<br><br>The current thesis conducted a nested case-control study using Primary Care Clinical Informatics Unit (PCCIU) database and a cohort study using the UK Biobank to assess the association between acid-suppression therapy and gastro-oesophageal cancer risk. The finding showed an increased risk of gastro-oesophageal cancer in patients using proton pump inhibitors and/or histamine-2 receptor antagonists but, particularly for gastric cancer, these associations appeared consistent with confounding by indications rather than a real causal association.<br><br>The apparent sex-disparities in gastro-oesophageal cancer risk remain largely unexplained.

The current thesis investigated pre-diagnostic circulating sex hormones and gastro-oesophageal cancer risk using the UK Biobank, and showed sex hormone binding globulin was positively associated with gastric cancer risk in men and suggested a role of testosterone in oesophageal cancer. Also, this thesis explored a variety of female reproductive factors in relation to the risk of gastro-oesophageal cancer mortality in the China Kadoorie Biobank.

Only higher number of pregnancies and induced abortions were found to be associated with reduced risk of gastric cancer mortality.<br><br>In summary, the current thesis has contributed to the literature by identifying exposures which could influence gastro-oesophageal cancer risk and progression. Future studies are required to replicate the novel associations observed.<br><br><br>