SUNDAY, May 15 (HealthDay News) -- Smoking increases the risk of advanced kidney cancer, researchers report.

In a new study, a team from Duke University Medical Center reviewed the cases of 845 patients who had had surgery for kidney cancer -- or renal cell carcinoma -- between 2000 and 2009. They found that current and former smokers were 1.5 to 1.6 times more likely to have advanced cancer than nonsmokers.

Heavy smoking (smoking for a longer period of time and smoking more) was associated with advanced renal cell carcinoma. Kicking the habit reduced the risk of advanced disease by 9 percent for every 10 years that a former smoker was smoke-free, the investigators found.

The findings were slated for presentation Sunday at a special press conference at the American Urological Association's annual meeting, in Washington, D.C.

Another study scheduled for presentation at the same briefing found that rates of bladder cancer did not fall along with lower rates of smoking in the United States.

The researchers examined a national database and found that lung cancer rates declined along with decreasing per capita consumption of cigarettes between 1973 and 2007, but the same type of consistent decline was not seen in bladder cancer rates.

There may have been a decrease in bladder cancer due to smoking, but that decrease may have been offset by other factors contributing to a rise in bladder cancer over the last few decades, the researchers at the State University of New York Upstate Medical University in Syracuse said in a news release from the American Urological Association.

"These two studies shed new insight into the role that smoking might have for two important urologic cancers," news conference moderator Dr. Toby Kohler said in the news release.

"For kidney cancer, it is true that kidney tumors are more often being detected these days when they are smaller. However, smoking seems to confer a much greater risk that the cancer may be more aggressive. Cessation of smoking seems to lower the risk," Kohler said.

"For bladder cancer on the other hand, the decrease in smoking rates has not impacted the incidence to the same degree that it has for lung cancer, suggesting that there may be other factors which are becoming more important for the development of the disease," he added.

Because these studies are being presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

More information

The U.S. National Cancer Institute has more about bladder cancer.