Mendelian randomization studies of cancer risk: a literature review.
Level 5 - mechanism / opinion, no new human data
Narrative literature review of observational Mendelian randomization studies without quantitative meta-analysis
PubMed 30034993 · doi:10.1007/s40471-018-0144-1
What was done
The authors searched the published literature through October 31, 2017, to identify human Mendelian randomization (MR) studies investigating the effects of lifestyle factors, physical traits, biomarkers, and other exposures on cancer risk. They synthesized findings across 76 identified MR studies to assess evidence of causal relationships.
What was found
Across 76 studies, the authors reported evidence of causal associations for several factors across specific cancer types: - Alcohol consumption increases risk for head/neck and colorectal cancers. - Adult body mass index (BMI) increases risk for multiple cancers, but decreases risk for breast cancer. - Height increases risk for breast, colorectal, and lung cancers, but decreases risk for esophageal cancer. - Telomere length increases risk for lung adenocarcinoma, melanoma, renal cell carcinoma, glioma, B-cell lymphoma subtypes, chronic lymphocytic leukemia, and neuroblastoma. - Hormonal factors affect risk for sex-steroid sensitive cancers. The abstract reports no numerical effect sizes or confidence intervals.
Why it matters
This review synthesizes the contribution of genetic instrumental variable methods to cancer etiology, highlighting that causal effects of exposures like BMI and height can vary substantially or act in opposite directions across different cancer types.
Limits
As a narrative review, the abstract provides no pooled quantitative effect estimates or formal meta-analytic evaluation. The underlying studies are subject to standard Mendelian randomization limitations, including pleiotropy and instrumental variable validity. The literature search captures studies only through October 2017.
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