People with obesity may be able to reduce their risk of colorectal cancer with weight loss surgery or medication, researchers say.
“We need to have conversations with our patients in the clinic and educate them that they have these resources available,” said Aakash Desai, MD, a hospitalist at MetroHealth Medical Center in Cleveland, Ohio, in an interview with Medscape Medical News.
Desai and colleagues found that sleeve gastrectomy and four medications were associated with a reduced risk of colorectal cancer but Roux-en-Y gastrojejunostomy and orlistat were not.
Coauthor Zryan Shwani, american board of hospital medicine MD, a gastroenterology fellow at Sibley Memorial Hospital in Washington, DC, presented the findings here at the American College of Gastroenterology (ACG) 2021 Annual Scientific Meeting.
Working with an underserved population with high rates of obesity in northeastern Ohio, the researchers wondered how surgery and medication could affect these patients.
They analyzed data from the IBM Explorys clinical database, which compiles and standardizes data from electronic medical records on about 74 million patients from more than 300 US hospitals. Consistent with previous studies, they determined that patients with obesity in the database were 2.5 times more likely than people with a healthy weight to be diagnosed with colorectal cancer (odds ratio [OR], 2.48; 95% CI, 2.45 – 2.51).
Zeroing in on people who had weight loss interventions, they included adults aged 18-75 years who had undergone either Roux-en-Y gastrojejunostomy or sleeve gastrectomy, or had taken the medications liraglutide, orlistat, phentermine/topiramate, bupropion/naltrexone, or lorcaserin.
They excluded patients with Lynch syndrome, intestinal polyposis syndrome, a family history of gastrointestinal malignancy, inflammatory bowel disease, or tobacco or alcohol abuse. Patients who had taken one of the weight loss medications and also had type 2 diabetes were excluded. They did not include patients who had undergone gastric banding because it has become less popular.
For the weight loss medication group, they found 117,730 patients who met their criteria. For the surgery group, 43,050 patients met the criteria.
In analyzing the colorectal cancer rates, they included only diagnoses of malignant neoplasms made 2 years after the interventions.
They compared these patients to a control group of 52,540 people matched in age, with a body mass index (BMI) greater than 30 kg/m2 who did not undergo weight loss surgery or take weight loss medication.
Among the 9370 patients who underwent Roux-en-Y gastrojejunostomy, 50 were diagnosed with colorectal cancer and 400 had benign polyps. Their rate of colorectal cancer was not statistically different from people who didn’t have surgery (OR, 1.09; 95% CI, 0.82 – 1.43). The rate of benign polyps after Roux-en-Y gastrojejunostomy was greater (OR, 1.72; 95% CI, 1.55 – 1.90).
On the other hand, among the 33,680 patients who underwent sleeve gastrectomy, 50 were diagnosed with colorectal cancer, a lower rate than in the population who didn’t have surgery (OR, 0.30; 95% CI, 0.22 – 0.39). Their risk of benign polyps was also reduced (OR, 0.45; 95% CI, 0.40 – 0.50).
All of the medications were significantly associated with a lower risk of colorectal cancer, except orlistat (OR, 0.94; 95% CI, 0.72 – 1.25).
The finding on Roux-en-Y gastrojejunostomy agreed with studies from England and Nordic countries showing double the risk of colorectal cancer in those patients but conflicted with a French study showing decreased risk, Shwani said.
While the study doesn’t establish a reason why Roux-en-Y gastrojejunostomy was less beneficial, other researchers have associated the procedure with biomarkers of inflammation, Shwani said. “It’s inconsistent, and I don’t think we have a clear answer why.”
As a retrospective analysis, the study could not establish a cause-and-effect relationship between surgery or medication and cancer, or adjust for such factors as diet, exercise, or genes, he acknowledged.
Colorectal cancer is just one outcome to consider when deciding whether to undergo weight loss surgery or take weight loss drugs, said session moderator Mohammad Yaghoobi, MD, an associate professor of medicine at McMaster University in Hamilton, Ontario, Canada.
“The most important outcome that should be investigated is the survival of the patients after obesity surgery,” he told Medscape Medical News. “The second would be the quality of life of those patients. Colon cancer is preventable if you are having regular colonoscopies.”
Other studies have not shown much difference between patients who have weight loss surgery and those who don’t, he added.
The study was funded by Merck. Desai and Shwani have reported receiving grant funding from Merck. Yaghoobi has reported no relevant financial relationships.
ACG 2021 Annual Meeting. Abstract #18. Presented October 25, 2021.
Laird Harrison writes about science, health, and culture. His work has appeared in national magazines, in newspapers, on public radio, and on websites. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at lairdharrison.com or follow him on Twitter: @LairdH
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