Gastric bypass surgery -- a treatment for obesity that is already known to reduce heart disease and diabetes -- decreases the incidence of cancer by 80% over the five years following the procedure, Canadian researchers reported Wednesday.
The incidence of two of the most common tumors, breast and colon, was reduced by 85% and 70%, respectively, Dr. Nicolas Christou of McGill University in Montreal said.
The study confirms the findings of two papers issued in August that showed the surgery reduced overall deaths from cancer. The new study goes a step further by showing reductions in the incidence of several specific types of cancer, said Dr. Philip Schauer of the Cleveland Clinic Lerner College of Medicine, who was not involved in the study.
"This is really powerful information," said Schauer, immediate past president of the American Society for Metabolic and Bariatric Surgery. "It reaffirms that obesity is a profound risk factor for cancer" and shows that "weight loss does seem to affect the development of new cancers."
But Dr. Edward H. Phillips, a bariatric surgeon at Cedars-Sinai Medical Center, was skeptical about the findings because cancer takes a long time to develop and the patients were studied for only five years.
He noted that it was now common for weight-loss surgery candidates to undergo mammograms, colonoscopies and endoscopies to screen for cancer before the procedure.
"It could be that we are selecting people out of the population who don't have cancer," biasing the results, Phillips said. He believes that losing weight will reduce the incidence of cancer but that it will take longer than five years for the effects to surface.
Christou countered that such screening "is not the standard of care" in Canada, where the subjects lived. Furthermore, many of the patients had undergone surgery as long as 15 years before the start of the study, he said, leaving plenty of time for cancer to develop.
There are two main types of bariatric surgery. The simpler is banding, in which an inflatable silicone band is placed around the stomach to reduce its capacity, allowing the patient to feel full after eating much less food.
In a gastric bypass, the stomach is sewn shut to reduce its capacity to 3 or 4 ounces, and the intestines are connected directly to the newly created pouch, bypassing part of the area where food absorption occurs. This is generally a more invasive surgery but produces greater weight loss.
