It’s known that severe kidney disease — requiring dialysis or a transplant — raises a person’s risk of developing cancer.
But even moderate kidney dysfunction may carry increased risk, according to a study by three health centers, including the University of Utah’s Huntsman Cancer Institute.
Researchers found that among 1.2 million older adults, those with stage 3 kidney disease were 39 percent to 100 percent more likely to be diagnosed with renal cancer over five years than people with stage 2 kidney disease.
Stage 3 patients were also 48 percent likelier to develop urothelial, or urinary bladder, cancer.
The study, published online Thursday in the Journal of the American Society of Nephrology, is not the first to link chronic kidney disease with cancer. But it’s probably the largest, said lead author William Lowrance, a professor of urology and cancer surgeon at Huntsman.
Researchers also analyzed patients’ glomerular filtration rate (GFR), a test to check how well the kidneys are functioning, or how much blood passes each minute through tiny, waste-removing filters in the kidneys.
They found the rate is an independent risk factor for renal and urinary bladder cancer — but not other cancer types — and “could have implications for directing cancer screening efforts in select populations,” said Juan Ordonez, a co-author and chairman of the Chiefs of Nephrology at Kaiser Permanente Northern California.
Roughly 10 percent of American adults, or 20 million people, have chronic kidney disease, according to the Centers for Disease Control and Prevention (CDC). Almost half of them have stage 3 disease, a moderate amount of kidney damage that may show no signs or symptoms.
Not everyone with moderate kidney disease will progress with worsening disease, and having kidney disease doesn’t necessarily lead to cancer, said Lowrance.
“It calls for further study to understand the biological mechanisms behind this,” he said. “Does [kidney disease] cause some type of inflammation or oxidative stress, or is the immune system compromised, allowing cancers to come through?”
There are currently no formal recommendations for screening for kidney cancer.
“Patients are usually screened for symptoms such as blood in the urine,” said Lowrance. “Over 70 percent of kidney cancers are detected incidentally. You go to the emergency room with an unrelated complaint and get a CT scan showing a mass on the kidney.”
For the study, researchers tracked 1.2 million adult patients of Kaiser Permanente, those age 40 and older with known kidney function and no history of cancer, dialysis or a kidney transplant.
Over 5.3 years about 73,000 were diagnosed with cancer.
Odds of renal cancer were elevated among those with stage 3 kidney disease, but especially for those with 3b kidney disease, the more advanced end of stage 3 disease. They had a twofold increased risk for renal cancer compared with adults in stage 2 with mildly reduced kidney function.
Lowrance’s team accounted for variables such as age, race and medications the patients were taking.
Risk was of greater magnitude for clear cell renal cancer, the most common type of kidney cancer, as compared non-clear renal cancer.
Researchers also showed a link to urinary bladder cancer, but no association was found with colorectal, lung, breast or other types of cancer.
The study was a collaborative effort by Kaiser’s research division, Huntsman and Memorial Sloan Kettering Cancer Center.