Obesity surgery may reduce cancer risk


Obesity surgery may reduce cancer risk


Two studies from Canada and Brazil announced at conferences earlier this week suggest that bariatric or weight-loss surgery to control obesity may also cut cancer risk.

The Canadian study was conducted by Dr Nicolas Christou of the McGill University Health Centre (MUHC) and McGill University in Montreal, Quebec, who reported his preliminary results to the 25th Annual Meeting of the American Society for Metabolic & Bariatric Surgery, in Washington DC, and the Brazilian study was conducted by Dr Alfredo Halpern, of the University of São Paulo, and colleagues. Halpern presented the results of his study to the The Endocrine Society's 90th Annual Meeting in San Francisco.

People who are obese have a significantly higher risk of developing several types of cancer, including breast, colon, esophagal and kidney cancer.

Christou said bariatric surgery is increasingly being used to help morbidly obese patients to lose up to 70 per cent of their excess weight and to maintain their weight loss. According to Halpern, research suggests the benefits include resolution of type 2 diabetes, reduced blood pressure and lower risk of premature death.

Reuters yesterday gave an estimated figure that 205,000 people underwent bariatric surgery in the United States in 2007.

For the Canadian study, Christou explained how bariatric surgery also decreased the risk of patients developing cancer by up to 80 per cent. Most of the patients in this study had gastric bypass surgery, a procedure that leaves the patient with a smaller stomach and allows food to bypass part of the small intestine.

Christou said:

"The relationship between obesity and many forms of cancer is well established. This is one of the first studies to suggest that bariatric surgery might prevent the risk of cancer for a significant percentage of morbidly obese people."

Christou and colleagues compared 1,035 morbidly obese patients who had bariatric surgery between 1986 and 2002 with 5,746 weight-matched patients who did not have the procedure.

During follow up, the number of cancer diagnoses in the bariatric surgery group was 85 per cent lower for breast cancer and 70 per cent lower for colon and pancreatic cancer, and there was also a lower rate for several other cancers such as skin cancer, uterine cancer and non-Hodgkin's lymphoma.

One reason for these results could be that excess body fat affects hormone metabolism, a known factor in the development of breast and colon cancer. However, the researchers said there were probably a number of reasons.

For the Brazilian study, Halpern and colleagues studied the effect of weight-loss surgery on the immune function of 20 women and 8 men who were morbidly obese and like the Canadian study, also had gastric bypass surgery that reduced stomach size and allowed food to bypass some of the intestine thus reducing food intake and absorption.

Halpern said there were few studies evaluating the immune function of severely obese patients and how surgery induced weight loss might affect it, and yet "obesity is related to a higher rates of infection and some types of cancer".

Six months after the operation, the patients had lost an average of 78.5 pounds (35.6 kilos). The researchers also took blood samples before surgery and 6 months after, to monitor levels in natural killer cells, which are important for controlling infection and fighting cancer.

In addition to measuring numbers of killer cells and their activity (presumed to increase their potential to kill infected cells or tumor cells), Halpern and colleagues also looked at the production of essential immune system proteins, the cytokines interferon-gamma and interleukins 2, 12 and 18.

The results showed that although the number of natural killer cells did not change after surgery, they were 79 per cent more active, suggesting this also increased their ability to fight infection and cancer. Cytokine activity had also increased.

Halpern said that reduced natural killer cell activity in extremely obese people could be a reason for them being more predisposed to infections and cancer, and that in this case, the weight-loss surgery may have helped to:

"Protect against infections and cancer by improving the activity of certain immune cells."

Plans to publish results of either study in peer reviewed journals were not mentioned in the press statements.

Click here for McGill University Health Centre.

Click here for University of São Paulo.

Sources: McGill University Health Centre, The Endocrine Society, Reuters.


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