Biopsy advised to verify RF ablation efficacy in RCC

August 1, 2006

Atlanta-As radiofrequency ablation emerges as a minimally invasive treatment option for small-cell renal carcinoma, urologists should consider including biopsy as a normal component of patient follow-up, say researchers from the Cleveland Clinic.

In a study involving 80 patients, Nicholas Hegarty, MD, PhD, and colleagues found that radiologic imaging alone often fails to detect early recurrence or persistent disease.

"Radiofrequency ablation is a technique in evolution. Close follow-up is required of all patients undergoing this treatment while its true efficacy is being determined. MRI follow-up appears to have certain limitations, and incorporation of biopsy into the follow-up protocol may provide useful information to determine treatment success," said Dr. Hegarty, clinical fellow in laparoscopic and robotic surgery at the Cleveland Clinic working with Inderbir S. Gill, MD, and colleagues.

"While radiological appearance can give a strong indication of whether complete ablation of the tumor has been achieved-with either RFA or cryoablation-we feel a biopsy should be included to help determine the outcome of therapy," Dr. Hegarty said.

Biopsy confirms outcomes

In this study, 80 patients underwent a total of 93 RFA treatments between January 2003 and October 2005. All were performed using the Starburst system (RITA Medical Systems, Inc., Fremont, CA), with patients under local anesthesia and sedation. Clinical and radiologic follow-up included MRI scans at 1 day, at 3 months, and at 6 months after RF ablation. Biopsy of the ablation site was scheduled at 6 months.

Of 62 patients for whom follow-up data of 6 months or longer were available, 45 showed evidence of a non-enhancing radiolesion on MRI. However, biopsy revealed active tumor in two patients (both of whom had no evidence of disease after a repeat RF ablation procedure in one case and after nephrectomy in the other).

Similarly, of 11 patients in whom radiolesions "with non-specific/faint enhancement" were found, two had tumor on biopsy. Neither patient showed evidence of disease after repeat RF ablation procedures. The remaining six patients' MRIs had enhancing areas suggestive of tumor, and three did, indeed, have tumors on biopsy. Five had no evidence of disease with repeat RF ablation, while the other patient was stable on observation.

"We consider uncovering several positive biopsies to be an important finding," Dr. Hegarty said. "Biopsy has been incorporated into the protocol at a few other centers besides our own, but in many of those places, it is performed immediately after or within a few days of treatment.

"The criticism there is that the presence of normal cancer cells at an early time point does not automatically imply that these cells will remain viable with follow-up. Thus, a 6-month time period was chosen, as it is reasonable to assume that the presence of cancer cells at that point would be strongly suggestive of viable cancer."

Dr. Hegarty added that even using skilled radiologists to read post-RF ablation MRI scans does not obviate the need for biopsy, pointing out that radiologists in the Cleveland Clinic study had "tremendous experience in MRI and, in particular, tremendous experience with interpretation of MRI following probe ablation of the kidney."