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More Data Favor Bariatric Surgery for Cutting CRC Risk

Among people with obesity, bariatric surgery may help reduce colorectal cancer (CRC) risk, according to a study from France.

In a nationwide cohort of individuals with obesity, and at roughly 6 years of follow-up, new CRC cases occurred in 0.6% of patients who elected bariatric surgery compared with 1.3% of those who did not (P<0.001), reported Laurent Bailly, MD, PhD, of the Centre Hospitalier Universitaire de Nice, and colleagues in JAMA Surgery.

In a subsample of patients matched for morbid obesity status, age, sex, body mass index, and other clinical characteristics, those who underwent bariatric surgery saw a 32% reduced risk for CRC versus nonsurgical patients (HR 0.68, 95% CI 0.60-0.77).

Among those who opted for bariatric surgery, the extent of risk reduction was greater for women:

  • Women: HR 0.66 (95% CI 0.57-0.77)
  • Men: HR 0.72 (95% CI 0.57-0.89)

While the findings in women were on par with previous research, the results overall came as a bit of a surprise to the researchers, according to Bailly.

“In obese individuals who did not undergo bariatric surgery, 12,629 new colorectal cancer cases were diagnosed, whereas only 9,417 cases were expected,” Bailly told MedPage Today. “On the contrary, in obese individuals who did undergo bariatric surgery, 423 new colorectal cancer cases were observed, whereas 428 cases were expected.”

People with obesity generally carry a 34% higher risk for developing CRC above that of the general population, and that risk can even jump as high as 80% higher in patients ages 50 to 59, Bailly pointed out. But after bariatric surgery, individuals with obesity share the same risk of CRC as the general population.

Benefits of bariatric surgery also extended to a reduction in benign colorectal polyps — those who underwent surgery saw a 44% risk reduction for benign polyps (HR 0.56, 95% CI 0.53-0.59), according to the authors.

Adjustable gastric banding, sleeve gastrectomy, and gastric bypass procedures were included in the analysis. In a comparison of the type of procedure performed, gastric bypass and sleeve gastrectomy patients saw slightly lower rates of new CRC diagnoses (0.5% for both) compared with adjustable gastric banding (0.7%). Similar patterns were seen in regards to procedure type and rate of benign colorectal polyps — 5% of adjustable gastric banding patients developed polyps versus only 3.1% of gastric bypass or sleeve gastrectomy patients.

For the analysis, Bailly’s group utilized French electronic health data on over 1,000,000 individuals with obesity (ages 50 to 75). All individuals were CRC free at baseline. Among this group, a little under 75,000 individuals opted to undergo bariatric surgery, with the majority choosing sleeve gastrectomy (35,300), followed by gastric bypass (22,300), and adjustable gastric banding (16,500).

Bailly said the authors conducted the study in order to clarify the questions surrounding these associations, as existing evidence is largely conflicting.

“Obesity is known to increase cancer incidence and notably colorectal cancer incidence. Bariatric surgery is an effective treatment of obesity, however the association of this surgery with the colorectal cancer remained controversial,” Bailly pointed out.

The latter point was highlighted in an invited commentary by Lance Davidson, PhD, of Brigham Young University in Provo, Utah, and Ted Adams, PhD, of the University of Utah in Salt Lake City. They noted that the findings are in line with a previous report that found a 41% reduced risk for incident colon cancer after bariatric surgery. However, both these reports conflict with another report that found a 55% higher risk for colon cancer incidence 10 to 14 years after bariatric surgery.

“These conflicting CRC-associated results imply that the jury is still out on whether bariatric surgery increases or decreases incident CRC risk,” Davidson and Adams argued.

They suggested future research on this topic account for study population differences, mechanistic variation of procedure type, and length of follow-up in order to most accurately address these questions.


Bailly and co-authors, as well as Davidson and Adams, disclosed no relevant relationships with industry.