Obesity Complicates Colorectal Cancer

Study finds that prediagnosis obesity is predictive of poor prognosis, even among patients who have a molecular marker associated with better disease outcome.

By Tracy Vence | April 9, 2014

WIKIMEDIA, PHAROSObesity can contribute to a poor prognosis for colorectal cancer patients, including those who have the tumor microsatellite instability (MSI) marker associated with better disease outcome, according to an unpublished analysis of data from a prospective study involving nearly 5,000 patients.

Researchers working with the American Cancer Society’s Tumor Repository found that patients who had a high body-mass index (BMI) before being diagnosed with colorectal cancer were more likely to have a poorer prognosis than those who had a healthy BMI. The same applied to even prediagnosis high-BMI patients who had MSI-high tumors. The negative impact of elevated BMI on colorectal cancer prognosis appeared to trump the so-called “protective” effects of elevated MSI, the team found.

“It was interesting to see the magnitude of the change in these groups,” said Peter Campbell, the director of Tumor Repository, who is presenting his team’s findings at the American Association for Cancer Research (AACR) annual meeting in San Diego, California, today (April 9). “We know obesity is associated with greater risk of mortality in a more general population. Why not with MSI-high CRC [colorectal cancer] patients, too?”

“They had a large, well-characterized population of individuals who had been diagnosed with colorectal cancer and the ability to follow up for a reasonable amount of time,” said Paul Terry, an epidemiologist at the University of Tennessee, Knoxville, who was not involved in the work. Terry noted, however, that colorectal cancer can “take 30 to 40 years to develop in many cases, and people go through metabolic changes over time,” so a deeper dive into the biology could be demonstrative.

“Simply collecting and harmonizing data from thousands of patients from multiple study centers was a major hurdle in this analysis,” Campbell added. “It took several months to get the data harmonized in a meaningful manner and a few weeks to analyze it properly,” he explained in an e-mail to The Scientist.  

“This [study] should provide a reference point for people to understand the potentially serious consequences of obesity and colorectal cancer,” said Terry. But, he asked, “are the tumors [of obese patients] qualitatively different?”

Campbell said his team will submit its findings for publication soon, and next plans to investigate how a colorectal cancer patient’s clinical and molecular statuses might together impact prognosis.  

“We hope to look more deeply into the joint impacts of molecular features and lifestyle factors on colorectal cancer incidence and survival,” he said.

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April 10, 2014

Is this an observational study with all of the limited predictive and generalisable power of such category of studies.

Is poor outcome an obesity factor, tumor factor or combination or others. The obese is also the physically difficult to palpate for any given biological stage and type of tumor: just as he will pose greater perioperative challenges than the non obese related to the BMI.

All of these will happen irrespective of the biology and stage of the cancer.

It will be interesting if the study can be randomly designed to tell if the obese is specifically prone to a particular biological species of tumors relative to his non obese control.

If diet has a role in tumor induction in colorectal cancers, and diet is also inductive of obesity ( for a given genetic trigger), then we begin to see a common factorial for both obesity and oncological phenotypes in colorectal cancer. It certainly will seem helpful to see the effect of obesity on outcomes in non colorectal cancers and non-cancerous pathologies.

Such comparative analyses may tell more about any apparent linearities between obesity and outcome patterns in colorectal cancers

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