CT-guided radiofrequency ablation effective in eradicating small malignant kidney tumors

Aug 3 2007

A relatively new, minimally invasive treatment was 100 percent successful in eradicating small malignant kidney tumors in a study of more than 100 patients, report researchers from Wake Forest University Baptist Medical Center.

The patients underwent CT-guided radiofrequency ablation (RFA) at Wake Forest Baptist for kidney tumors ranging in size from 0.6 cm to 8.8 cm. A total of 125 tumors in 104 patients were treated over the period 2000 to 2006. In all of the patients, a biopsy had confirmed the presence of renal cell carcinomas (RCC), a common type of renal malignancy.

Of 95 tumors that were smaller than 3.7 cm (about 1.5 in.), all were completely eradicated by a single treatment, along with 14 of the larger tumors. Seven more of the 16 remaining larger tumors were eradicated after a second treatment, for a total 93 percent success rate for all 125 tumors. The results, reported in the August issue of the American Journal of Roentgenology , were based on follow-up exams over an average of about 14 months.

“This is the largest treatment group to date of patients with biopsy-proven renal malignancies,” said Ronald J. Zagoria, M.D., a professor of radiology at Wake Forest Baptist, an associate in urologic surgery, and lead author on the study. “The results – a high cure rate and low complication rate – establish that at institutions with experience doing this procedure, this is an alternative method for treating small renal malignancies in patients who are not good surgical candidates.”

RFA uses a needle-like treatment probe, guided by computed tomography (CT) as it is inserted through the skin into the tumor. The probe's high-frequency alternating current heats the tumor tissue and destroys it. The technique has been used successfully in liver tumors since the early 1990s and has more recently been adapted for treatment of RCC.

“Renal cell carcinomas that are smaller than 3.7 cm in diameter can be reliably and safely eradicated with percutaneous RFA,” Zagoria and his colleagues conclude in the report. “This result is regardless of the location or position of the RCC in the kidney.

Larger tumors can also be eradicated with percutaneous RFA, they say, but with the larger tumors the risk of incomplete tumor destruction increases substantially. The authors also note that larger tumors near the middle of the kidney may be more difficult to ablate, possibly because they are close to large blood vessels or the ureter.

RFA is an outpatient procedure in which the patient is sedated but conscious and a local anesthetic is used at the puncture site. In the study being reported, 101 of the 104 patients went home the same day, and three were hospitalized after the procedure – one for a planned treatment, another for treatment of bruising around the puncture, and a third for treatment of exacerbation of a heart condition.

A total of eight patients experienced complications, including temporary air pockets in the chest cavity, mild to severe pain after the procedure, pneumonia, and problems with their ureters. Generally, the report says, “this study shows that the procedure ... has a very low rate of complications.”

Standard treatment for RCC has been a removal of the affected kidney, along with adjoining blood vessels and lymph nodes, known as a “radical nephrectomy,” although newer minimally invasive techniques, such as laparoscopic surgery, have also been used successfully.

Zagoria cautioned that RFA is not recommended if patients are good surgical candidates who are healthy, younger, and have two normal kidneys, because long-term follow-up is lacking and therefore the durability of cure is not confirmed. (The average age of patients in the study was about 70, with a range of 30-89.) However, he said, “I think this is a big advance in treating renal tumors.”

The best candidates for RFA, he said, are patients with increased risk of complications from surgery and those with an hereditary condition that makes it likely they will require repeated treatments because of continual development of RCCs.

Zagoria's co-authors on the report are Michael A. Traver, M.D., David M. Werle, M.D., Molly Perini, and Satoru Hayasaka, Ph.D., all with Wake Forest Baptist, and Peter E. Clark, M.D., now at Vanderbilt University School of Medicine.

Wake Forest University Baptist Medical Center is an academic health system comprised of North Carolina Baptist Hospital and Wake Forest University Health Sciences, which operates the university's School of Medicine. The system comprises 1,154 acute care, psychiatric, rehabilitation and long-term care beds and is consistently ranked as one of “America's Best Hospitals” by U.S. News & World Report.