SOURCES: Mahboob Rahman, M.D., associate professor, medicine, Case Western Reserve University School of Medicine, Cleveland; Beth Piraino, M.D., president, National Kidney Foundation; April 23, 2014, presentation, National Kidney Foundation annual meeting, Las Vegas
WEDNESDAY, April 23, 2014 (HealthDay News) -- Older adults with moderate kidney dysfunction may face a higher risk of developing cancer than those with healthy kidneys, a large study suggests.
Researchers found that among nearly 32,000 older U.S. adults, those with stage 3 kidney disease were more than 40 percent likelier to be diagnosed with cancer over five years, versus people with normal kidney function.
Experts stressed that the findings do not necessarily mean that kidney disease itself leads to cancer.
"There is no way for a study like this to prove cause-and-effect," said senior researcher Dr. Mahboob Rahman, of Case Western Reserve University School of Medicine in Cleveland.
He said the findings, scheduled for presentation Wednesday at the National Kidney Foundation's annual meeting in Las Vegas, "should be considered preliminary."
Still, the results are "important," and warrant more study, said Dr. Beth Piraino, president of the National Kidney Foundation.
"We're not trying to scare people. But this is something they should be aware of," said Piraino, who was not involved in the study.
She added that people with kidney disease may want to be especially vigilant about curbing their cancer risks -- by, for example, not smoking, maintaining a healthy weight and having recommended cancer screenings.
In the United States, about 11 percent of adults -- or over 23 million people -- have chronic kidney disease, according to the U.S. Centers for Disease Control and Prevention. Almost half of them have stage 3 disease -- a moderate amount of kidney damage that may cause no obvious signs or symptoms.
In fact, many people with kidney disease do not know it, Piraino said.
Key risk factors for chronic kidney disease include diabetes and high blood pressure. Some medical groups say individuals with those conditions should be screened for kidney problems. Screening involves a blood test to see how well the kidneys are filtering waste products from the body.
For the new study, Rahman's team looked at data on 31,896 older adults with high blood pressure. Over five years, over 2,500 people -- or about 8 percent -- were diagnosed with cancer.
Overall, the odds were elevated for people with stage 3b kidney disease, which is the more advanced end of stage 3. Compared with older adults with healthy kidneys, their cancer risk was 43 percent higher, the study found.
Rahman's team accounted for factors such as age, race and diabetes, and the higher cancer risk persisted. But, he said, it's impossible to say why.
A buildup of minerals and waste products could be one possibility.
"We can only speculate," Rahman said. "But since the kidneys clear toxins from the body, it's possible that decreased kidney function could increase the risk of cancer."
"We need a lot more research to understand what is going on," he added. "This is very preliminary information."
One question is whether people with kidney disease have elevated rates of only certain types of cancer.
For now, Rahman and Piraino said older adults should keep seeing their doctor and working on getting risk factors for kidney disease under control. Maintaining a healthy weight and blood pressure levels, eating right, and not smoking are some of the ways to protect your kidneys from damage as you age. Avoiding excessive use of pain medications is also important.
Data and conclusions presented at meetings are typically considered preliminary until published in a peer-reviewed medical journal.
The National Kidney Foundation has more on chronic kidney disease.