Contrast-enhanced ultrasound (CEU) may improve doctors’ ability to distinguish potentially dangerous renal tumors from relatively benign or indolent ones, according to a pilot study.

Used with other diagnostic criteria, the technique—which involves intravenous injection of a contrast medium consisting of gas-filled lipid microspheres—could help clinicians decide which tumors should be removed surgically and which can be managed conservatively.

The investigators, led by Scott Gerst, MD, Associate Attending Radiologist at Memorial Sloan-Kettering Cancer Center in New York, noted in a report in the American Journal of Roentgenology (2011;197:897-906), that, to their knowledge, no established noninvasive way exists to differentiate—definitively and preoperatively—low-grade or benign malignant tumors from the more aggressive clear cell tumors, which have a higher risk of metastasis.

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“Contrast-enhanced ultrasound of renal masses is a promising new tool which may provide added value over standard, noncontrast-enhanced ultrasound, and improves our ability to image and evaluate these lesions without radiation or the risk of either contrast-induced nephropathy or nephrogenic systemic fibrosis,” Dr. Gerst told Renal & Urology News.

By one set of enhancement criteria, the CEU technique had a 75% positive predictive value for determining whether a tumor was a non-clear-cell carcinoma. Using other criteria, the technique had an 85% positive predictive value for predicting whether a tumor was conventional clear-cell carcinoma or another kind of tumor.

“We therefore predict, although more data are needed, that in select patient populations such as those with contraindications to intravenous CT or MRI contrast, or patients with high surgical risk, contrast-enhanced ultrasound will have a role,” Dr. Gerst said.

Commenting on the new study, urologist Christopher G. Wood, MD, who has conducted extensive research on renal cancer, observed: “This and other studies highlight the true value of CEU, which is the capacity to image renal lesions and assess vascular flow, without the need for radiation or nephrotoxic contrast agents. This technology will greatly aid our ability to image patient lesions preoperatively, as well as follow patients post-operatively after non-extirpative therapies such as thermal ablation.”

Still, patient age, tumor size, presence or absence of symptoms related to the mass, and the presence of significant co-morbid conditions will play a much greater role than CEU in deciding how patients will be managed, said Dr. Wood, Professor of Urology at the University of Texas M.D. Anderson Cancer Center in Houston.

“In my opinion,” he said, “the use of CEU may add some small increment of information used to formulate a treatment plan for a given patient, be it active surveillance, energy ablation, or surgery, but it certainly will not be a decisive factor in predicting the biologic potential of a given tumor.”