LAS VEGAS – The ability of bariatric surgery and substantial subsequent weight loss to cut the incidence of a variety of obesity-related cancers and other malignancies received further confirmation in results from two studies reported at a meeting presented by the Obesity Society and the American Society for Metabolic and Bariatric Surgery.
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Dr. Andrea M. Stroud
In one study, 2,107 adults enrolled in the Longitudinal Assessment of Bariatric Surgery (LABS-2) study showed a statistically significant halving of the cancer incidence during 7 years of follow-up in patients who underwent bariatric surgery and had a reduction of at least 20% in their presurgical body mass index (BMI), compared with patients in the study who underwent bariatric surgery but lost less weight, reported Andrea M. Stroud, MD, a bariatric surgeon at the Oregon Health & Science University, Portland.
In the second study, analysis of about 1.7 million hospitalized U.S. patients in the National Inpatient Sample showed that the incidence of an obesity-related cancer was 21% higher in more than 1.4 million obese individuals (BMI, 35 kg/m2 or greater) with no history of bariatric surgery, compared with nearly 247,000 people in the same database with a history of both obesity and bariatric surgery, said Juliana Henrique, MD, a bariatric surgeon at the Cleveland Clinic Florida in Weston.
The study reported by Dr. Henrique focused specifically on the 13 cancer types identified by the Centers for Disease Control and Prevention as having an incidence that links with overweight and obesity (Morb Mortal Wkly Rep. 2017;66[39]:1052-8), whereas the study presented by Dr. Stroud included all incident cancers during follow-up, but which were predominantly obesity related, with breast cancer – an obesity-related malignancy – having the highest incidence. Overall, 40% of all U.S. cancers in 2014 were obesity related, according to the CDC’s report.
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Dr. John Scott
“A number of studies have shown decreases in cancer rates after bariatric surgery, especially female cancers like breast and ovarian,” commented John Scott, MD, director of metabolic and bariatric surgery for Prism Health–Upstate in Greenville, S.C. “These two reports build on that.”
The evidence for weight loss after bariatric surgery as a means to cut the risk of a first or recurrent cancer has become strong enough for some patients to see cancer prophylaxis as a prime reason to undergo the procedure, said surgeons at the meeting.
Bariatric surgery and subsequent weight loss “is a substantial preventive factor for cancer, especially in patients who have obesity and diabetes,” commented Theresa LaMasters, MD, a bariatric surgeon in West Des Moines, Iowa. “It might not just be weight loss. It’s likely a multifactorial effect, including reduced inflammation after bariatric surgery, but weight loss is a component” of the effect, Dr. LaMasters said in an interview. It is now common for her to see patients seeking bariatric surgery because of a family or personal history of cancer. “Patients are trying to reduce their future risk” for cancer with bariatric surgery, she added.
The LABS-2 study enrolled 2,458 patients who were part of the first LABS cohort, LABS-1, but followed them longer term. The data Dr. Stroud reported came from 2,107 of the LABS-2 patients without a history of cancer, no cancer diagnosed in the first year after bariatric surgery, and longer-term follow-up of 7 years. About three-quarters of the patients underwent gastric bypass, with the rest undergoing laparoscopic gastric band placement. Nearly half of those included had diabetes. Their average BMI was 45-50 kg/m2.
Dr. Stroud and associates ran an analysis that divided the populations into tertiles based on percentage of baseline body mass lost at 12 months after surgery and cancer-free survival during the 7 years after the 12-month follow-up. The incidence of cancer was 51% lower in patients who lost 20%-34% of their BMI, compared with those who lost less than 20%, a statistically significant difference, and patients who lost 35% or more of their BMI had a 31% reduced cancer rate, compared with those who lost less than 20%, a difference that was not statistically significant, Dr. Stroud reported. The patients who lost less weight after surgery mostly underwent gastric banding, whereas those who lost more mostly underwent gastric bypass.
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Dr. Juliana Henrique
The analysis reported by Dr. Henrique used data collected in the U.S. National Inpatient Sample during 2010-2014, which totaled more than 7 million patients hospitalized for cancer, including 1,423,367 with a history of obesity and 246,668 with obesity who had undergone bariatric surgery. Those without bariatric surgery had a 21% higher rate of developing obesity-related cancers after adjustment for many baseline demographic and clinical features, Dr. Henrique said. The cancer protection after bariatric surgery was especially notable in the subset of patients in the sample with a genetic predisposition to developing cancer.
LABS-1 and LABS-2 were funded by the National Institute of Diabetes and Digestive and Kidney Diseases. Dr. Stroud and Dr. Henrique had no disclosures.
SOURCES: Stroud AM et al. Obesity Week, Abstract A107; Henrique J et al. Obesity Week, Abstract A108.