Obesity’s contribution to cancer risk may be substantially underestimated because of limitations in how it is typically measured in epidemiologic studies, according to a Viewpoint published in JAMA Oncology.
Zilin Luo, MBBS and colleagues described the PLUS framework, which identifies four factors that could bias risk estimates downward: prediagnostic weight loss, reliance on single-point rather than lifetime weight exposure, use of body mass index (BMI) instead of central obesity measures in some settings, and conventional BMI thresholds that may not capture risk below 25.
Prediagnostic weight loss is a key concern. The researchers noted that a large proportion of weight loss in patients with gastrointestinal cancers occurs before clinical detection, which may lead to underestimation of BMI when measured near the time of diagnosis.
The Viewpoint also highlights limitations of single-time-point BMI measurements, which may not reflect cumulative exposure to excess weight, as well as evidence that waist circumference may better capture risk associated with visceral adiposity in some populations.
In an example cited by the researchers using UK Biobank data, the population-attributable fraction for obesity-related gastrointestinal cancers increased from 7% to 18% after excluding early postrecruitment cases, which may be affected by prediagnostic weight loss.
The researchers suggested that these factors, taken together, may lead to underestimation of obesity’s role in cancer development and that prevention strategies could have a larger impact than previously recognized. “Emerging evidence indicates that its attributable cancer burden has been strongly underestimated,” Luo and colleagues wrote. They called for integrating obesity control more fully into cancer prevention and public health frameworks.
The Viewpoint also noted that available interventions have mixed evidence. Bariatric surgery has been associated with reduced risk for several obesity-related cancers, although some studies have reported increased colorectal cancer risk after certain procedures. Observational data on glucagon-like peptide-1 receptor agonists suggest potential benefits but also raise questions about risks for some cancers, including kidney and thyroid malignancies.
Further research is needed to clarify these associations and to refine approaches to risk assessment, the researchers wrote.
The authors reported no conflicts of interest.
Source: JAMA Oncology