Evidence supporting kidney RFA grows stronger

Clinical data are mounting to show that radiofrequency ablation of small kidney tumors is a safe, 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 previously deemed unsafe.

Sizable, long-term survival trials comparing RFA and surgery for the treatment of renal cell carcinomas have yet to be published. Several midterm follow-up reports, however, note the implications of lesion size and location as well as proper patient selection for RFA success. Studies also suggest that interventional radiologists could successfully ablate nearly 100% of tumors provided they observe technical and clinical considerations.

Dr. Debra A. Gervais and colleagues at Massachusetts General Hospital's radiology and urology departments 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 plus single-tip and cluster probes were used 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 found 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. Complications affecting the bowel were rare, mostly as a result of protective strategies including proper probe placement and hydro dissection (AJR 2005;185:64-71, 72-80).

The same research group also published results on 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).

Another investigative team from the University of Texas published results of a new RFA technique for kidney tumors formerly considered too risky to cook due to 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 technique allowed for safe, precise placement and repositioning of the RFA probe into the kidney's upper pole under CT guidance (AJR 2005; 185:86-88).

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. IRs should consider these and other variables to select the right candidates and also to present patients with treatment choices, particularly if RFA proves to be a valid alternative to surgery in the future, the researchers said.

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, they said.

For more information, visit Diagnostic Imaging's Tumor Ablation Clinic or click on the following links from the Diagnostic Imaging archives:

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