Excess Weight Tied to Poorer Colorectal Cancer Outcomes

Marcia Frellick

November 06, 2019

SAN ANTONIO — It has long been known that underweight patients with colorectal cancer have a poor prognosis, but new research indicates that this association holds true for patients who are overweight as well.

"We found that obese and underweight colorectal mortality were not significantly different from each other," said researcher Vita Jaspan, a fourth-year medical student at the NYU School of Medicine in New York City.

In fact, she and her colleagues found that the rate of cancer-related mortality was higher in obese than in normal-weight patients, that the odds of disease-free survival was lower, and that the likelihood of a recurrence of colorectal cancer was higher.

Although doctors might talk to their patients about weight, it is usually in the context of cardiac health. The maintenance of a healthy weight has not traditionally been thought of as a way to improve colorectal cancer outcomes or avoid recurrence, Jaspan said here at the American College of Gastroenterology 2019 Annual Scientific Meeting.

But "if there's something patients can do to make their prognosis better, they should be aware of it," she told Medscape Medical News. "I don't think that's been shared with patients yet."

Our results are very consistent and show that being underweight or obese are equally bad in terms of long-term prognosis.

Jaspan and her colleagues conducted a systematic review and meta-analysis of 251,347 people with stage I to III nonmetastatic colorectal cancer who were followed for 31 months to more than 15 years.

The researchers found 41 studies that met their criteria and were included in the final analysis. Median age in the pool of patients was 61.8 to 71.0 years.

"There was already a lot of evidence supporting the link between obesity and risk of colorectal cancer, but there were fewer data on how obesity affected outcomes," Jaspan said. "There's also this idea of the obesity paradox, where the obesity is thought to be potentially protective in cancer and other chronic diseases," as described in a 2016 study published in JAMA Oncology.

In fact, "there is no evidence that overweight patients, as measured by BMI, should be encouraged to lose weight in the postdiagnosis period," said Candyce Kroenke, ScD, the lead author of that study, at the time of publication, as reported by Medscape Medical News.

However, it is not clear how long the protective effect of excess weight lasts or at what point a patient should be encouraged to lose weight, Kroenke and her colleagues acknowledge.

"The current literature reflects both sides, which is why we chose to do the meta-analysis," said Kevin Lin, a fourth-year medical student at the NYU School of Medicine and a member of Jaspan's research team.

"We wanted to see which effect was stronger," Jaspan explained.

Jaspan, Lin, and their colleagues hypothesized that outcomes would be worse for obese than for normal-weight patients, but better for overweight than for underweight patients.

However, their findings showed that obese patients had higher rates of colorectal cancer recurrence than normal-weight patients, and that there was no significant difference in recurrence between overweight and underweight patients.

Table. Rates of Colorectal Cancer Recurrence
Weight Categories Compared Odds Ratio 95% Confidence Interval
Obese vs normal 1.47 1.02–2.12
Overweight vs normal 1.41 1.18–1.69
Underweight vs obese 0.74 0.29–1.86

"Our results are very consistent and show that being underweight or obese are equally bad in terms of long-term prognosis," Jaspan reported.

The biggest implication of these data is that "in treating cancer, weight may play an independent role in outcomes," said Jonathan Leighton, MD, a gastroenterologist from the Mayo Clinic in Phoenix.

"The findings are thought-provoking at the very least. I am not aware if there are previous studies looking at that detail," he told Medscape Medical News

Future prospective studies should look at whether it is an association or whether there is cause and effect, he added.

American College of Gastroenterology (ACG) 2019 Annual Scientific Meeting: Oral abstract 72. Presented October 30, 2019.

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