In a German study reported in JAMA Oncology, Li et al found that assessment of risk of colorectal cancer based on cumulative lifetime excess weight may be more accurate than risk indicated by single body mass index (BMI) measurements.
As stated by the investigators, “Excess weight is associated with increased cancer risk, but the risk may have been underestimated, as previous studies did not consider cumulative lifetime exposure.”
The analysis used data from a population-based case-control study conducted since 2003 in Germany. Height and self-reported weight—documented in 10-year increments starting at age 20, up to the participant’s current age—were obtained from 5,635 persons who developed colorectal cancer and 4,515 persons serving as controls.
BMI was calculated for each year of age from age 20 years to current age by linear interpolation. Excess BMI (eBMI) at each year of age was defined as BMI ≥ 25 kg/m2 and summed across ages to obtain the weighted number of years lived with overweight or obesity (WYOs).
The mean age of patients with colorectal cancer was 68.4 years, and 59.7% were men. The mean age of controls was 68.5 years, and 61.1% were men.
Compared with controls, patients with colorectal cancer had a significantly higher BMI at each decade of age (eg, 26.6 vs 25.8 kg/m2 at age 50 years) and significantly higher prevalence of overweight and obesity at each age (eg, 45.7% vs 43.3% overweight and 17.1% vs 11.4% obese at age 50 years).
On multivariate analysis, compared with participants who remained within normal weight range (0 WYOs), risk for colorectal cancer increased significantly with each increasing WYO quartile: adjusted odds ratios were 1.25 (95% confidence interval [CI] = 1.09–1.44) for quartile 1, 1.41 (95% CI = 1.23–1.61) for quartile 2, 1.60 (95% CI = 1.40–1.83) for quartile 3, and 2.54 (95% CI = 2.24–2.89) for quartile 4.
Each standard deviation increase in WYOs was associated with an adjusted odds ratio for colorectal cancer of 1.55 (95% CI = 1.46–1.64). This odds ratio was higher than the odds ratio of 1.27 (95% CI = 1.16–1.39) per standard deviation increase of eBMI at any single point of time.
The investigators concluded, “The results of this case-control study suggest a greater role of cumulative lifetime excess weight for colorectal cancer risk than estimated by traditional analyses based on BMI measures taken at a single point.”
Hermann Brenner, MD, MPH, of the Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Heidelberg, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was funded by the German Research Council, German Federal Ministry of Education and Research, and others. For full disclosures of the study authors, visit jamanetwork.com.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.