ANN ARBOR, Mich. -- The number of cases of kidney cancer has been rising over the last two decades, and new research from the University of Michigan Comprehensive Cancer Center shows that this increase is driven largely by the detection of small, presumably curable, kidney masses. But even though the rising incidence has been paralleled by greater use of surgery for kidney cancer, this trend has not led to fewer people dying.
"With increased early detection and treatment of small tumors, we would expect to see a decrease in mortality associated with kidney cancer," says senior author Brent K. Hollenbeck, M.D., assistant professor of urology at the U-M Medical School. "Surprisingly, that's not what we found. Our research shows that an increase in detection and treatment is not leading to a reduction in the kidney cancer mortality rate."
The study published in the Sept. 20 issue of the Journal of the National Cancer Institute includes data from nine of the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) registries. In all, the researchers examined data from 34,503 patients with kidney cancer.
Over the study period (1983 to 2002), researchers observed a rise in the occurrence of kidney cancer (also known as renal cell carcinoma) for tumors of all sizes. But the greatest increases in kidney cancer incidence were among tumors 4 centimeters or smaller. Tumors of this size, often found in patients without any clinical signs or symptoms, are being detected more and more with the widespread use of abdominal imaging studies, such as MRIs and CAT scans. These small kidney tumors are considered curable by surgery, which has led to a rise in surgery for kidney cancer.
Even as early detection and surgical treatment increased, however, mortality rates caused by kidney cancer during the time period rose dramatically, from 1.2 to 3.2 deaths per 100,000 people in the United States.