Cancer surveillance, obesity, and potential bias
Authors: Andrew G Renehan, Richard M Martin, D Gareth Evans
Journal: The Lancet Public Health (2019)

Although Hyuna Sung and colleagues1Sung H Siegel LR Rosenberg PS Jemal A Emerging cancer trends among young adults in the USA: analysis of a population-based cancer registry.Lancet Public Health. 2019; 4: e137-e147Summary Full Text Full Text PDF PubMed Scopus (244) Google Scholar stressed caution in interpreting their ecological study in The Lancet Public Health (March, 2019), the naive reader—or the media, as was the case2Laura Donnelly, for The Telegraph. “Shocking” rise in obesity-related cancers among young adults.https://www.telegraph.co.uk/news/2019/02/04/shocking-rise-obesity-related-cancers-among-young-adults/Date: Feb 4, 2019Date accessed: February 8, 2019Google Scholar—might conclude that obesity is fuelling the reported disproportionate temporal increases in incidence of obesity-related cancers in young adults. However, there are many arguments against obesity as a causal driver. First, as the accompanying Comment3Marinac CR Birmann BM Rising cancer incidence in younger adults: is obesity to blame?.Lancet Public Health. 2019; 4: e119-e120Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar highlighted, the biological mechanisms for many early-onset cancers are distinct from those of late-onset cancers. In colorectal cancer, the malignancy in which increases among young adults are most striking, the molecular phenotype of early-onset cancer is often an aggressive consensus molecular subtype (CMS), such as CMS-1 or CMS-3, whereas obesity-related cancers generally follow a more canonical CMS-2 pathway. Second, the Article by Sung and colleagues1Sung H Siegel LR Rosenberg PS Jemal A Emerging cancer trends among young adults in the USA: analysis of a population-based cancer registry.Lancet Public Health. 2019; 4: e137-e147Summary Full Text Full Text PDF PubMed Scopus (244) Google Scholar failed to demonstrate sex or racial specificity, which are hallmarks of the obesity–cancer relationship.4Renehan AG Zwahlen M Egger M Adiposity and cancer risk: new mechanistic insights from epidemiology.Nat Rev Cancer. 2015; 15: 484-498Crossref PubMed Scopus (368) Google Scholar Finally, the fundamental premise in age–period–cohort modelling attributes cohort effects to modifiable lifestyle or environmental factors, at the absolute rejection of short-term changes in population-level genetic susceptibility. This method ignores the contributory role of epigenetic effects (for example, methylation), which can influence short-term trends. There is a need for a concerted effort from the research community to bring together wide-ranging disciplines to disentangle the causes of this emerging public health problem. The linked Comment3Marinac CR Birmann BM Rising cancer incidence in younger adults: is obesity to blame?.Lancet Public Health. 2019; 4: e119-e120Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar advocates for “further close epidemiological monitoring”. We champion a wider approach, such as that captured by triangulation5Lawlor DA Tilling K Davey Smith G Triangulation in aetiological epidemiology.Int J Epidemiol. 2016; 45: 1866-1886PubMed Google Scholar (the combination of evidence from studies that yield causal estimates with different potential sources of bias, but where these biases are independent), and inclusion of the use of non-conventional approaches, such as instrumental variable analyses. AGR reports speaker honoraria from Merck Serona and Jenssen-Cilag in the last 2 years, outside the scope of this Correspondence. DGE reports other from AstraZeneca, outside the scope of this Correspondence. RMM declares no competing interests. AGR and DGE are supported by the Manchester NIHR Biomedical Research Centre (IS-BRC-1215-20007). Cancer surveillance, obesity, and potential biasWe congratulate Hyuna Sung and colleagues1 for their analyses of cancer trends among young adults in the USA.1 The authors observed an increase in the incidence of several obesity-related cancers in this population. However, they might have overlooked the effect of cancer surveillance bias on these trends. Full-Text PDF Open AccessEmerging cancer trends among young adults in the USA: analysis of a population-based cancer registryThe risk of developing an obesity-related cancer seems to be increasing in a stepwise manner in successively younger birth cohorts in the USA. Further studies are needed to elucidate exposures responsible for these emerging trends, including excess bodyweight and other risk factors. Full-Text PDF Open Access