Kidney tumor RF ablation gets stronger, more versatile

A substantial amount of clinical data shows that radiofrequency ablation of small kidney tumors is a safe and effective alternative to open or laparoscopic resection. Distinct intervention protocols and complementary techniques could further boost RFA's efficacy and expand its application to areas where it was previously deemed unsafe.

Sizable long-term survival studies comparing RFA and surgery for the treatment of renal cell carcinoma have yet to be published. Several midterm follow-up reports, however, note the implications of lesion size, location, and proper patient selection for the technique's success.

Studies also suggest that interventional radiologists could successfully ablate nearly 100% of tumors, provided that they observe technical and clinical specifications.

Dr. Debra A. Gervais and colleagues in the radiology and urology departments at Massachusetts General Hospital retrospectively reviewed almost six years' worth of data on 85 inoperable patients with 100 biopsy-confirmed renal cell carcinomas. An interventional radiologist, in consultation with two radiologists, performed 114 CT-guided and 12 ultrasound-guided RFA sessions. Two RFA generators and single-tip and cluster probes were used interchangeably, depending on lesion size.

After a mean patient follow-up of 2.3 years, the investigators found that all tumors 3 cm and smaller and all exophytic tumors regardless of size achieved complete necrosis. Size and location proved to be independent predictors of complete necrosis after a single ablation session (p< 0.0001 and p = 0.0049, respectively).

Complications included one inflammatory mass, one skin burn, two ureteral injuries, two transient lumbar plexus pain episodes, and five hemorrhages. Patients were treated conservatively, and none died from RFA-related complications.

The investigative team also found that the initial electrode position and the ablation zone's proximity to the collecting system did not influence ablation results or increase the risk of complications. Bowel morbidities proved rare, due mainly to protective strategies such as proper probe placement and hydrodissection (AJR 2005;185:64-71,72-80).

The same group also published results from 16 patients with renal cell carcinomas who underwent RFA as a curative treatment. All patients with exophytic tumors were successfully treated. The authors concluded that RFA of exophytic kidney tumors smaller than 5 cm matched survival rates for surgery at four years (J Urol 2005;174[1]:61-63).

An investigative team from the University of Texas published results of a new technique to treat kidney tumors formerly considered too risky to ablate percutaneously because of their proximity to the lungs.

Dr. Kamran Ahrar, an associate professor of interventional radiology at the M.D. Anderson Cancer Center, used a 20-gauge Chiba needle to induce a pneumothorax in the pleural cavity. The air-filled space allowed the interventional radiologist to place the RFA probe through the thorax and reach tumors located on the kidney's upper pole without piercing nor charring the lung.

The technique allowed for safe, precise percutaneous placement and repositioning of the RFA probe under CT guidance (AJR 2005;185:86-88).

"Some centers perform a CT of the kidney in prone position to see if the lung would be in the way of their electrode, and if so, they would do the RFA in the operating room with laparoscopy or open surgery. The technique we described helps the radiologist treat those patients in the interventional radiology suite," Ahrar said.

In addition to small malignancies, exophytic kidney tumors are well suited for RFA because of the insulating and cooling effects of surrounding fat and large blood vessels. Interventional radiologists should consider these and other variables in selecting candidates and presenting patients with treatment choices. That would be particularly important if RFA proves to be a valid alternative to surgery in the future.

Until long-term follow-up studies comparing RFA and surgery become available, however, RFA should be considered only as a promising, minimally invasive alternative in patients who can't undergo surgery, the researchers said.

Reimbursement for kidney RFA is available, but payment policies vary. Some payers refuse to cover RFA if surgery can't be ruled out. Specific CPT codes are under development and should be available by 2006, Ahrar said.