The most common type of kidney tumor is smaller than 3.8 cm and is often found incidentally on CT scans performed for other reasons. A biopsy is then performed to determine if the tumor is cancerous.

"Biopsies are not entirely free of pain and discomfort," said study co-author Dr. Jeffrey Cadeddu, a professor of urology and radiology at UT Southwestern. "Some patients, in fact, choose to observe the cancer simply to avoid the pain of the biopsy."

Study co-authors Dr. Ivan Pedrosa (left) and Dr. Jeffrey Cadeddu (right). Image courtesy of UT Southwestern.

The cohort included 110 patients with a total of 121 masses. The mean tumor size was 2.4 cm, and 50% of the lesions were clear cell carcinoma.

The mpMRI studies were performed on both 1.5-tesla and 3-tesla MRI scanners at several institutions. Sequences included T2-weighted, axial chemical shift T1-weighted, and dynamic contrast enhanced T1-weighted imaging. Because diffusion-weighted MR images were routinely acquired at UT Southwestern -- but not always at other facilities -- the researchers did not evaluate results using that sequence (Journal of Urology, October 2017, Vol. 198:4, pp. 780-786).

Seven radiologists independently reviewed the results; the radiologists had different levels of experience and were blinded to the final pathology findings. Their task was to rank the likelihood of clear cell carcinoma on a six-point scale, with 1 as "definitely not" cancer and 5 as "definitely" cancer.

By setting a parameter score of 4 or greater for clear cell carcinoma, the researchers achieved sensitivity of 78% and specificity of 80%. With a score of 3 or greater, sensitivity increased to 95% but specificity slipped to 58%. Interobserver agreement was moderate to good with a mean of 0.53.

"Using mpMRI, multiple types of images can be obtained from the renal mass and each one tells us something about the tissue," said co-author Dr. Ivan Pedrosa, a professor of radiology and chief of MRI, in a press statement. "Using mpMRI, doctors at UT Southwestern have a four-in-five chance of identifying clear cell cancer."

For patients, the goal is to help them "avoid the anxiety and the fear and the rare, but possible, complication of a biopsy," Cadeddu said. By doing so, "I think we're pushing medicine forward."