A phenome-wide Mendelian randomization study of pancreatic cancer using summary genetic data

Background: The 5-year mortality rate for pancreatic cancer is amongst the highest of all cancers. Greater understanding of underlying causes could inform population-wide intervention strategies for prevention. Summary genetic data from genome-wide association studies (GWAS) have become available for thousands of phenotypes. These data can be exploited in Mendelian randomization (MR) phenome-wide association studies (PheWAS) to efficiently screen the phenome for potential determinants of disease risk.

Methods: We conducted an MR-PheWAS of pancreatic cancer using 486 phenotypes, proxied by 9124 genetic variants, and summary genetic data from a GWAS of pancreatic cancer (7,110 cancer cases; 7,264 controls). Odds ratios and 95% confidence intervals per 1 SD increase in each phenotype were generated.

Results: We found evidence that previously reported risk factors of body mass index (1.46; 1.20 to 1.78) and hip circumference (1.42; 1.21 to 1.67) were associated with pancreatic cancer. We also found evidence of novel associations with metabolites that have not previously been implicated in pancreatic cancer: fibrinogen-cleavage peptide (1.60; 1.31 to 1.95) and O-sulfo-L-tyrosine (0.58; 0.46 to 0.74). An inverse association was also observed with lung adenocarcinoma (0.63; 0.54 to 0.74).

Conclusions: Markers of adiposity (BMI and hip circumference) are potential intervention targets for pancreatic cancer prevention. Further clarification of the causal relevance of fibrinogen cleavage peptides and O-sulfo-L-tyrosine in pancreatic cancer aetiology is required, as is the basis of our observed association with lung adenocarcinoma.

Impact: For pancreatic cancer, MR-PheWAS can augment existing risk factor knowledge and generate novel hypotheses to investigate.