PSC vs UC and hepatobiliary cancer risk

What is known

• The mediating (indirect) effect of PSC on UC-to-hepatobiliary-cancer was 0.083, representing 73.8% of the total effect, while the direct effect of UC was only 0.029 (total 0.113). ¹
• Genetic susceptibility to PSC significantly increased hepatobiliary cancer risk (IVW OR 1.855), whereas UC showed no direct causal effect on hepatobiliary cancer. ¹
• UC causally increased PSC risk (IVW OR 1.145) with no evidence of reverse causality, supporting a UC-to-PSC-to-cancer pathway. ¹
• After PSC diagnosis the annual incidence of cholangiocarcinoma is about 1-2% with a 5-10% lifetime cumulative risk, and PSC patients also face elevated gallbladder cancer risk. ^1,2

What is unknown / caveats

• Most cited hepatobiliary-cancer-specific causal evidence comes from a single Mendelian randomization study (PMID 39732896); other abstracts focus on colorectal rather than hepatobiliary neoplasia
• MR study used only European-descent GWAS data, limiting generalizability
• Subgroup analyses by sex, age, and comorbidity were constrained
• Several older abstracts address colorectal cancer risk, not hepatobiliary cancer, so cannot directly inform the direct-vs-mediated question
• Whether PSC acts as a complete versus partial mediator is not fully resolved, since a small non-significant direct UC effect remained.

References

1. Wang F, Xiao J. The mediating role of primary sclerosing cholangitis in the association between ulcerative colitis and hepatobiliary cancer investigated through Mendelian randomization. Sci Rep. 2024. PMID: 39732896.

2. Lee JW, Moon W. Are the risks of colorectal cancer and biliary cancer really increased if patients with ulcerative colitis have primary sclerosing cholangitis?. Intest Res. 2023. PMID: 37139591.

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Draft, generated by the IBDology RAG and not yet clinician-reviewed. Answers are grounded in the retrieved literature listed above; a high faithfulness score means the answer matches its sources, not that the sources are correct.