Radiofrequency Ablation Wipes Out Small Kidney Tumors

WINSTON-SALEM, N.C., Aug. 1 -- One-time percutaneous radiofrequency ablation proved completely successful in eradicating small malignant kidney lesions, found researchers here.

Of 95 renal cell carcinomas smaller than 3.7 cm, all were destroyed by a single treatment, along with 14 of 30 larger tumors (mean size 4.7 cm), reported Ronald J. Zagoria, M.D., of Wake Forest University here, and colleagues, in the August issue of the American Journal of Roentgenology.

Patients were followed with contrast-enhanced CT or MRI. Tumor control was defined as the absence of contrast enhancement in the tumor on CT or MRI.

Seven of 16 remaining larger tumors were eradicated after a second treatment for a 93% success rate for 116 of 125 lesions with a mean follow-up of 13.8 months, wrote the researchers.

With each 1-cm increase in tumor diameter greater than 3.6 cm, the likelihood of tumor-free survival decreased by a factor of 2.19 (P

Treatment of larger tumors, the researchers said, may result in an increased risk of residual tumor. The authors also noted that tumors larger than 3.6 cm located in the medial half of the kidney may have an increased likelihood of incomplete ablation, possibly because they are close to large blood vessels or the ureter.

Of nine patients who did not respond to treatment, two had a nephrectomy, and two were retreated with RF ablation, one unsuccessfully and one lost to follow-up. Two others were retreated and were found to have residual tumors on follow-up scans, and three others were followed conservatively because of poor overall health.

Among the study's limitations, the researchers wrote, is the possibility that the lack of tumor detectable on CT or MRI does rule out microscopic foci of viable neoplasm.

Also, they noted that the lack of a large series of patients with follow-up of more than five years means it is not possible to prove from this study that tumor eradication will be durable over many more years.

Dr. Zagoria cautioned that ablation is not recommended if patients are good surgical candidates, are healthy, younger, and have two normal kidneys, because long-term follow-up is lacking and durability of cure is not confirmed.