Obesity may improve survival rate of kidney cancer

By David Douglas

NEW YORK (Reuters Health) - Although obesity increases the risk of developing kidney cancer, patients with greater body mass index (BMI) seem to have less aggressive disease, according to researchers. BMI, the ratio of weight to height, is a common means of estimating whether someone is overweight or underweight.

Although obesity appears to double the risk of developing kidney cancer, also referred to as renal cell carcinoma, there is some evidence that those with a greater BMI at the time of diagnosis may have a better outcome, Dr. Alexander S. Parker of the Mayo Clinic, Jacksonville, Florida and colleagues report in the medical journal Urology.

To investigate further, the researchers studied data from 970 patients who underwent surgery for clear cell renal cell carcinoma, the most common type of kidney cancer.

Less aggressive tumors were more likely to be found in patients who were considered to be overweight (having a BMI of 25 to 29), or obese (having a BMI 30 or greater), compared with patients who were underweight or normal weight.

The 5-year survival rate from kidney cancer was 82 percent for obese patients, 77 percent for overweight patients and 62 percent for normal-weight patients.

Compared with normal-weight patients, the risk of death from clear cell renal cell carcinoma was reduced by 52 percent for obese patients and by 36 percent for overweight patients. However, the researchers point out that BMI adds little in the way of prognostic information beyond that afforded by available methods.

Nevertheless, Parker told Reuters Health that the relationship between less aggressive tumors and higher BMI "needs to be further evaluated to determine if this is due to increased screening and early detection among obese individuals, or if obese patients really do develop less aggressive tumors."

"If the latter is true," he concluded, "this would have the potential to tell us exciting new things about how renal clear cell carcinomas develop and how best to treat them."

SOURCE: Urology, October 2006.