TUESDAY, June 23, 2009 (HealthDay News) -- Obese women who have weight-loss surgery may reduce their risk of developing cancer, but there appears to be no such benefit for men, Swedish researchers report.
Obesity is associated with an increased risk of developing many different cancers. In the United States, obesity is linked with 14 percent of cancer deaths in men and 20 percent of such deaths in women, according to background information in the study.
Data from the Swedish Obese Subjects (SOS) study had previously shown that bariatric surgery has favorable effects on body weight, diabetes, other cardiovascular risk factors, heart structure and function, and health-related quality of life. "We now show a strong reduction in the female cancer incidence," said lead researcher Dr. Lars Sjostrom, a professor in the Department of Body Composition and Metabolism at Sahlgrenska University Hospital in Gothenburg, Sweden.
The report is published in the June 24 online edition of The Lancet Oncology.
For the study, Sjostrom and colleagues collected data on 2,010 obese patients who underwent weight-loss surgery and compared them with 2,037 obese patients who did not have surgery.
People who underwent surgery lost about 44 pounds, while those who didn't gained about 3 pounds, according to the report.
Over almost 11 years of follow-up, the researchers found that women who had weight-loss surgery lowered their risk of cancer by 42 percent compared with women who did not have the surgery. There was no reduction in the risk for cancer among obese men who had the surgery, the study authors noted.
"Bariatric surgery is reducing cancer incidence in women but not in men," Sjostrom said. "The favorable effect of bariatric surgery could not be demonstrated to be mediated by weight loss or reduced energy intake."
New research is needed to understand the gender difference, Sjostrom said. "Mechanisms need to be studied separately in men and women. If the favorable effect in women is not mediated by weight loss or reduced energy intake, it must be mediated by something else," he said.
Andrew G. Renehan, from the Department of Surgery in the School of Cancer and Imaging Sciences at the University of Manchester in the United Kingdom, and author of an accompanying journal editorial, says this study together with data from other studies show that weight reduction through bariatric surgery is associated with cancer prevention.
"This study adds strength that the association between obesity and cancer risk is causal," Renehan said. "As the beneficial effects of weight reduction appear to favor women, there is a need to further research the mechanisms underpinning associations between body fat and cancer development."
Renehan stated, "Obesity causes cancer, but the obesity epidemic is not abating and we now have proof that we can reverse the effect of obesity on cancer risk."
Another expert thinks bariatric surgery, although expensive, saves money in the long run.
"For those of us who have practiced bariatric surgery, this is no surprise," said Dr. Mitchell Roslin, chief of bariatric surgery at Lenox Hill Hospital in New York City. "We know if you get rid of excess fat a whole lot of things get better."
Bariatric surgery should not be seen as the treatment of last resort, Roslin said. "Seeing this as the treatment of last resort will wind up costing us more. We will be paying for years of diabetes, we will be paying for years of heart disease, we will be paying for years of cancer treatment," he said.
Dr. Len Lichtenfeld, deputy chief medical officer at the American Cancer Society, said avoiding obesity in the first place is the best way to reduce your risk of cancer.
"The American Cancer Society believes that maintaining a healthy body weight, eating a healthy diet and exercising are important in our efforts to reduce the risk of cancer," Lichtenfeld said. "The question is how do we create a culture where children and adults are focused on healthier lifestyles and better alternatives so we don't have to be facing this increasing epidemic of obesity."
For more on obesity and cancer, visit the U.S. National Cancer Institute.