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Can Cancer Risk Be Melted Away Along with Excess Body Fat?

Women who underwent bariatric surgery had substantially lower risk for cancer.

In addition to its adverse metabolic and cardiovascular effects, obesity is associated with excess risk for cancer. In a prospective study, investigators in Sweden followed 2010 obese patients (1420 of whom were women; BMI 38 kg/m²) who underwent bariatric surgery and 2037 obese controls (1447 of whom were women) who received standard care and who were matched with surgical patients for factors such as age, weight, and smoking status. Surgery resulted in sustained mean weight loss of 20 kg; effects on overall incidence of fatal and nonfatal cancer (based on Swedish National Cancer Registry data) were evaluated in >99% of participants during a median follow-up of 11 years.

Overall, patients who underwent bariatric surgery had a lower risk for incident cancer than did control patients (hazard ratio, 0.67; P<0.001). This beneficial effect was observed in women (HR, 0.58; P=0.0001) but not in men (HR, 0.97); it was seen for various types of cancer and in association with all surgical techniques. Of note, reduction in cancer risk was not related to amount of weight lost.

Comment: These important results add to the evidence that obesity is a risk factor for cancer and suggest that substantial weight loss can partially mitigate this risk. Because this was not a randomized clinical trial, the data are not definitive. However, the large number of participants, high degree of retention, consistent ascertainment of malignancy, and long follow-up all strengthen the conclusions. Those patients who chose to undergo bariatric surgery might have had other socioeconomic attributes that influence cancer incidence, which could help explain why the amount of weight loss was not linked to reduction in cancer risk. Nonetheless, the data are intriguing and well worth discussing with patients who are considering weight-loss surgery.

— Anna Wald, MD, MPH

Published in Journal Watch Women's Health June 24, 2009

Citation(s):

Sjöström L et al. Effects of bariatric surgery on cancer incidence in obese patients in Sweden (Swedish Obese Subjects Study): A prospective, controlled intervention trial. Lancet Oncol 2009 Jun 24; [e-pub ahead of print]. (http://dx.doi.org/10.1016/S1470-2045(09)70159-7)

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• Can Cancer Risk Be Melted Away Along with Excess Body Fat?
  Bruce J Relyea, 29 Jun 2009 4:19 PM EST
  This is a well written article. As stated, because this was not a randomized clinical trial, the data are not... [more]
• Yet another reason to lose weight!
  Alwin C. Lewis, Burbank, Calfiornia, 30 Jun 2009 4:59 PM EST
  Need patients any more reasons to lose weight? And the best way to lose weight is to reduce the amount... [more]