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Is cryoablation better than radiofrequency ablation for a small renal mass?

Radiofrequency ablation is preferable.

Radiofrequency ablation (RFA), a high-tech version of electrocautery devices, kills cells using temperatures above 70[degrees]C. Radiofrequency is the preferred technology for most liver, breast, bone, and lung lesions. It is coagulative and permits incisional biopsies after treatment, especially when performed laparoscopically. This allows us to treat anticoagulated patients, which cannot be done comfortably with cryoablation.

Another advantage of RFA is that one probe fits all. With cryotherapy for tumors greater than 2-3 cm, you have to place multiple probes, and every time you place a probe you increase the chance of human error and tumor spillage. When there are problems with RFA, they're usually due to targeting, not to inadequate heat.

As for treatment candidates, we like to reserve RFA for clinical T1a tumors.

For the percutaneous approach, there has been more cumulative experience with RFA than with cryoablation. In fact, it is the preferred way of treating these tumors. If tumors are posterior or lateral and there are no adjacent structures, we would use the percutaneous approach, reserving the laparoscopic approach only for anterior lateral tumors or tumors with neighboring structures such as bowel.

We have now treated 116 tumors in this fashion at our medical center. The tumors were T1a and had an average size of 2.5 cm. In the vast majority of cases, we used anesthesia. General anesthesia allows more precise targeting, and primarily for that reason I believe our results are better than those reported in the literature. Our mean ablation time is 15 minutes, and our procedure time is 114 minutes.

We have limited follow-up to 2 years on average, with the longest being 4 years. Our post-RFA protocol is similar to that used for cryoablation, in which we periodically image patients every 6 months following an initial CT or MRI at 6 weeks. Our laparoscopic experience is less extensive, but here again we have acceptable operative times.

Blood loss needs to be highlighted, because RFA is a coagulative technology and bleeding is not an issue. We've never had more than 100 cc of blood loss in a single case at 2-year follow-up. For all comers, we recently published data on 94 patients with at least 12 months of follow-up. We had a 98% successful ablation rate on first go-round. Most procedures were done percutaneously and under general anesthesia. The recurrence-free survival rate was 97% at a mean follow-up of 25 months. A total of 24 patients have been followed beyond 3 years (J. Endourol. 2006;20:569-73).

In patients with biopsy-proven renal cell carcinoma, we saw a 96% successful ablation rate and 96% recurrence-free survival. Renal cell-specific survival was 98% at 25 months.

The most important issue, however, extends beyond this debate and involves the role of urologists in performing percutaneous tumor ablation, because that's how the tumors will be treated in the future. If urologists do not actively select, schedule, and participate in these treatments, it's not unreasonable to think that within 10 years these tumors will be treated by radiologists and then sent to us for follow-up.

Dr. Cadeddu is associate professor of urology and radiology at the University of Texas Southwestern Medical Center, Dallas.


Cryoablation is preferable.

We've had experience with about 200 cryoablations and 100 RFA procedures. Although partial nephrectomy remains the standard procedure for removing these small kidney tumors, there are indications for ablative therapy.

We perform laparoscopic cryoablation under general anesthesia, inserting one or more probes under CT monitoring with real-time ultrasound. The procedure also is done percutaneously as an outpatient procedure under sedation and a local anesthetic.

Because cryoablation is a new procedure, we conduct periodic follow-up with MRIs, and we biopsy the ablated side at 6 months. Biopsies show that most kidneys have fibrosis, and some have inflammatory cells and necrosis, but there have been no ghost tumor cells as reported in the RFA literature.

We've used cryoablation to treat about 200 cases with a mean tumor size of 2.3 cm. Of these patients, 66 completed 5-year follow-up with minimal morbidity. Among those completing a mean follow-up of 72 months, three had recurrences and one died of cancer, which is a 5-year survival of 81% and a cancer-specific survival of 98%.

Why not do RFA? In the RFA mechanism of tissue ablation, there is a complex relationship among power, current, and impedance. If the current is too low, the lesion is too small; if the current is too high or applied fast, there will be charring, insulation, and limited current flow.

With cryotherapy, the conduction of heat rests on a simple equation: Thermal conduction takes place through ice, and ice has a constant thermal conductivity K--so the value is always known, and you will always have a reliable ice ball progression.

With RFA, there are too many technical variables: Do you choose wet or dry? Do you choose temperature-based or impedance-based RFA?

And there are several choices of RFA needles: Do you use single tined or multitined?

While monitoring temperature during RFA, we have noticed that if any of the tines had charring or insulation, some would be hot and others would be cooler, so the heating was not always predictable.

Certainly, RFA is less expensive, but the one probe you use is replaced to do overlapping lesions. That may be misleading in 3-D space, and you may miss areas between the lesions, especially because there is no ice ball to follow.

With RFA, skipped lesions represent a very serious issue. In 2002, the Leahy Clinic in Boston performed RFA followed by partial nephrectomy. They found residual, viable tumors in every case. After performing cryoablation, they found no residual tumors.

When it comes to urine leak, the research data fall on the side of cryoablation. With regard to pain, researchers at Johns Hopkins found that "percutaneous cryoablation appears to require less analgesic than RFA."

In cryoablation, the technique is standardized and achieves an excellent success rate, while RFA is still an evolving technology.

Dr. Kaouk is codirector of robotic urologic surgery in the Cleveland Clinic's laparoscopic surgery section.

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Author:Cadeddu, Jeffrey; Kaouk, Jihad
Publication:Internal Medicine News
Geographic Code:1USA
Date:Nov 1, 2006
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