High Prediagnosis BMI Is a Predictor for Poor Outcome in Colorectal Cancer Patients, Overriding Tumor Marker Linked to Better Prognosis

Key Points

  • Patients with invasive colorectal cancer with a higher prediagnosis BMI had an increased risk of all-cause mortality after diagnosis, even those whose tumors harbored the microsatellite instability marker (MSI) usually associated with better prognosis.
  • Every 5 kg/m2 increase in BMI increased risk of all-cause mortality by 10%.
  • Similar associations were seen for both all-cause and colorectal cancer–specific mortality in patients with MSI-high and MSI-stable/MSI-low tumors.

A large prospective study of patients with invasive colorectal cancer has found that higher body mass index 2 years before diagnosis increased risk of all-cause mortality after diagnosis, even in patients whose tumors harbored a marker that is usually associated with better prognosis. The study was presented at the American Association for Cancer Research (AACR) Annual Meeting 2014 in San Diego.

Study Details

Participants in the study were identified from a multicenter cohort of 6,763 patients with invasive colorectal cancer who were enrolled in the Colon Cancer Family Registries from 1997 to 2008. The patients’ body mass index (BMI) status 2 years before diagnosis was calculated from self-reports of height and weight. Presence or absence of tumor microsatellite instability (MSI), a marker that is usually linked with better prognosis, was available for 4,987 patients.

Increased All-Cause and Colorectal Cancer–Specific Mortality

The researchers found that higher BMI 2 years before diagnosis increased risk for all-cause mortality after diagnosis, even in patients whose tumors harbored MSI.

After a maximum of 13.7 years of follow-up from enrollment to the end of the study (median, 5.3 years), the researchers found that every 5 kg/m2 increase in BMI increased the risk of all-cause mortality by 10%. Similar associations were seen for patients with MSI-high and MSI-stable/MSI-low tumors: Every 5 kg/m2 increase in BMI increased the risk of all-cause mortality by 19% and 8%, respectively.

The researchers also found that similar patterns of association were seen for colorectal cancer–specific mortality: Every 5 kg per m2 increase in BMI increased the risk of colorectal cancer–specific mortality by 7%. The association between high prediagnosis BMI and increased mortality after a colorectal cancer diagnosis was consistent for both men and women.

“Now that we have seen that obesity attenuates the survival advantage observed for patients with MSI-high tumors, we are looking at how it affects other tumor markers that have relevance for colorectal cancer survival,” Peter T. Campbell, PhD, lead author of the study and Director of the Tumor Repository in the Epidemiology Research Program at the American Cancer Society in Atlanta, said in a statement. “Ultimately, we would like to investigate associations between obesity and somatic tumor mutations to see if we can figure out how obesity drives cancer.”

The study data show that maintaining a healthy body weight throughout life is very important and also suggest that clinicians should consider prediagnosis BMI when managing patient care, added Dr. Campbell.

The study was funded by the National Institutes of Health and the National Cancer Institute. Dr. Campbell reported no conflicts of interest.

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®.


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