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Bariatric Surgery Cuts Women's Cancer Risk

Study Shows 42% Drop in Cancer Risk After Women Get Obesity Surgery

By Daniel J. DeNoon
WebMD Health News

Reviewed By Louise Chang, MD

June 23, 2009 -- Bariatric surgery cuts cancer risk by a "very strong" 42% in obese women -- but apparently not in obese men.

The finding comes from a 10-year Swedish study that already has shown that obese men and women cut their death risk by nearly 30% if they undergo bariatric surgery rather than try to lose weight some other way.

Now Lars Sjostrom, MD, PhD, of Gothenburg University, and colleagues show that very obese women who undergo bariatric surgery -- gastric bypass or various kinds of banding -- are significantly less likely to get cancer than obese women who do not have surgery.

"A 42% risk reduction is a very strong effect," Sjostrom tells WebMD. "Statin drugs are widely used to reduce risk of heart attack, a risk they reduce by 20%. So compared with the statin effect, this is strong."

The effect was not seen in men. This may be because many tumors are linked to sex hormones, and such cancers are more common in women than in men, says Mitchell Roslin, MDF, chief of obesity surgery at Lenox Hill Hospital, New York. Roslin was not involved in the Sjostrom study.

"There are a lot of fat-induced tumors and likely this has to do with the fact that many are linked to sex hormones, which are fat soluble," Roslin tells WebMD. "When people are morbidly obese, the amount of hormonal changes you see are remarkable. Women have infertility, irregular menses, very heavy periods -- these are the not very obvious implications of obesity."

Despite seeing cancer risk reduced only in women, Sjostrom says the findings hold out hope to men as well.

That's because of a mysterious finding: Protection against cancer risk was not directly linked to the amount of weight women lost or to the smaller amount of food they ate.

"If we could understand which mechanism mediates the protection after gastric surgery, it might be possible to influence this in a favorable way with drugs or nonsurgical interventions," Sjostrom says. "So it is extremely important to understand the mechanism by which surgery reduces cancer risk in women. Then we can start to develop cancer protective treatments we don't understand at all today."

In an editorial accompanying the Sjostrom study, cancer surgeon Andrew G. Renehan, MD, PhD, of the University of Manchester, U.K., says it's encouraging to learn that obesity-related cancers can be reversible.

"The cancers that link with obesity tend to be nonsmoking related -- breast cancer, endometrial cancer, colon cancer, and kidney cancer," Renehan tells WebMD. "We have spent four decades reducing smoking. Now there is a whole new list of cancers for which we can reduce risk."

Renehan hopes that people don't get the idea from the study that it's OK to get obese.

"These results now give us a platform to design studies in less grossly obese patients, using less invasive techniques to try and prevent cancer," he says.

Roslin agrees that it's better to prevent obesity -- or treat it early -- than to wait until surgery is the only option.

"Fat cells are very, very active cells. What we are seeing across a lot of disease spectrums is if you treat obesity aggressively, everything else gets remarkably better," he says. "We should be treating people earlier with less intense treatments than later. That means we need to put every single one of our resources together to prevent obesity."

But once someone is extremely obese, there's no time to waste on ineffective treatment.

"If behavioral treatment does not work in a short time, we should go quickly to surgical procedures," Roslin says. "Then our patients are less likely to be disabled, less likely to get chronic diseases like diabetes and heart disease -- and now we can say they are less likely to get cancer."

The Sjostrom study, and the Renehan editorial, appear in the June 24 early online edition of The Lancet.

SOURCES: Sjostrom, L. The Lancet, early online edition, June 24, 2009. Renehan, A.G. The Lancet, early online edition, June 24, 2009. Sjostrom, L. The New England Journal of Medicine, Aug. 23, 2007; vol 357: pp 741-752. Adams, T.D. The New England Journal of Medicine, Aug. 23, 2007; vol 357: pp 753-761. Andrew G Renehan, MD, PhD, department of surgery, School of Cancer and Imaging Sciences, University of Manchester, U.K. Lars Sjöström, MD, PhD, Sahlgrenska University Hospital, Gothenburg, Sweden. Mitchell Roslin, MD, chief of obesity surgery, Lenox Hill Hospital, New York.

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