Risk-stratification is like "picking out the bad apples and leaving the good behind," says Brady chief resident Mark Ball, M.D. Because so many tumors — as many as 30 percent of small kidney tumors that are surgically removed — are found to be benign, Ball and colleagues have been working on ways to help predict the risks of kidney tumors.

In a study led by Ball and recently published in the journal, Urologic Oncology: Seminars and Original Investigations, the investigators studied more than 1,000 patients from five different hospitals and identified factors associated with a higher risk of being cancer. Men were at higher risk of having cancer than women; other risk factors include a tumor size greater than 3 centimeters, and a high nephrometry score (a measure of tumor complexity on CT scan). "Patients with all three risk factors had an 89-percent chance of having cancer," says urologist Mohamad Allaf, M.D., the study's senior author, "while patients with none of these risk factors have only a 64-percent chance of having cancer." Ball adds: "This nomogram can help us do a better job of predicting which patients are more likely to have cancer, but it's not enough yet. Better tests are still needed to predict which patients can forego surgery, and who needs aggressive treatment."

In other recent findings, published in The Journal of Urology, the team studied how areas of a kidney tumor may look different (or heterogeneous) under the microscope. "We found that even the most aggressive tumors have areas that look less aggressive under the microscope," says Ball, who was the study's lead author. This may mean that biopsies are not that helpful. "Renal mass biopsy is sometimes used before surgery to confirm the diagnosis, but it's not a perfect test, and our study shows that it can sometimes give false reassurance," says urologist Phillip Pierorazio, a coauthor of the study.