Body mass index (BMI) at the time of diagnosis and after diagnosis is associated with risk of death in patients with colorectal cancer, a study published in JAMA Oncology has shown.1

Although previous research has attempted to determine the relationship between BMI and colorectal cancer outcomes, methodologic limitations have prevented the ability to definitive conclusions. Therefore, researchers sought to evaluate the association of BMI with colorectal cancer mortality in a complete population using causal diagrams.

For the retrospective observational study, investigators analyzed prospectively collected data from 3408 patients diagnosed with stage I to III colorectal cancer between 2006 and 2011 who had undergone surgery.

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Results showed that BMI at the time of cancer diagnosis was associated with all-cause mortality, with patients who were underweight and patients who were class 2 or 3 obese demonstrating increased risk of death compared with patients who were low-normal weight.

In contrast, researchers found that patients who were high-normal weight, low-overweight, and high-overweight had lower mortality risks than patients who were low-normal weight. There was no difference in mortality risk between patients who were class 1 obese and those who were low-normal weight.

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The study further demonstrated that the risks of colorectal cancer-specific mortality were similar to the risks of all-cause mortality, as was the association between postdiagnosis BMI and mortality; however, patients who were class 1 obese had significantly lower all-cause and cancer-specific mortality risks.

These findings ultimately suggest that recommending weight loss in the immediate period after cancer diagnosis in patients who are overweight may be unwarranted.                         


  1. Kroenke CH, Neugebauer R, Meyerhardt J, et al. Analysis of body mass index and mortality in patients with colorectal cancer using causal diagrams [published online ahead of print May 19, 2016]. JAMA Oncol. doi: 10.1001/jamaoncol.2016.0732.