Mayo Clinic physicians perform new procedure to treat kidney tumors

Tuesday, November 06, 2001

JACKSONVILLE, Fla., Nov. 6, 2001 — Physicians at Mayo Clinic in Jacksonville, Fla., are performing a new procedure as an alternative to surgery for treatment of kidney tumors. Called radiofrequency ablation, the procedure is proving effective for select patients. The best candidates have small tumors on the kidney surface that are not too close to other vital abdominal structures. In addition, the physician must be able to reach the tumor through the patient's abdomen with a special probe that delivers tumor-killing heat.

About 28,000 Americans are diagnosed each year with kidney cancer. The most common is renal cell carcinoma. The majority of these small tumors are incidentally detected on MRIs, ultrasounds or CT scans performed for reasons other than suspected kidney cancer. The conventional treatment for renal cell carcinoma that has not spread (metastasized) to other tissue is to remove all or part of the affected kidney.

Many people diagnosed with kidney tumors are not good candidates for the open surgical procedure, however. Age and other health problems can complicate recovery, and some patients cannot tolerate loss of part or all of a kidney. For these reasons, physicians have often opted to watch and wait. "That's a well-established way of dealing with small tumors in people who really shouldn't have surgery because a number of these cancers will never become a problem to the patient," says Mayo Clinic interventional radiologist Dr. Ricardo Paz-Fumagalli. However, doctors can't tell patients with certainty that their tumors will not grow and become a problem. That's why some patients prefer to attempt a cure and not take chances with observation alone.

Radiofrequency ablation can usually be done with only sedation and local anesthesia. A few patients will need general anesthesia if the procedure is expected to take longer than usual or doctors expect patients to feel pain from sensitive structures near the tumor.

To perform the radiofrequency ablation procedure, the physician inserts a special needle probe through the patient's skin, and guided by ultrasound, places it on the surface of the tumor. The physician then pushes a plunger on the probe that pushes an array of prongs out of the needle. "The prongs are embedded in the target tissue and define a spherical volume that will be subjected to the treatment," Paz-Fumagalli says. "You start applying alternating current at the frequency of radio waves. This produces frictional heat. Once the target temperature is reached, the tumor is heated for a period of time defined by its size — 20 minutes for a 4-centimeter-wide sphere of tissue, for example."

Paz-Fumagalli prefers to treat tumors no bigger than 4 centimeters across. He says the larger the tumor, the more likely it is that part of it will remain viable after the procedure.

Once the treatment is finished, the physician pulls the needle out, cauterizing its own track as it's removed. Most patients stay in the hospital for observation and go home the same day. Some may need an overnight stay for pain control. "Patients may feel some inflammatory response immediately after the procedure," says Mayo Clinic urologist Dr. Raul Parra. "They are sent home with oral analgesics or anti-inflammatories, and they may also temporarily see some blood in the urine." Parra is one of the clinic's urologists, who along with Paz-Fumagalli, selects patients for the procedure. Patients get follow-up CT scans every six months to make sure blood vessels supplying the tumor are gone and the tumor is shrinking.

Radiofrequency ablation is not new; doctors have used it since the mid-1990s for liver tumors. Only recently have they begun applying the technology percutaneously (through the skin) on kidney tumors. Parra and Paz-Fumagalli began using radiofrequency ablation to treat kidney tumors last year. Thus far, the procedure has been effective in shrinking or killing tumors in all but one of their 12 patients. "If radiofrequency ablation is not satisfactory, then we can do the surgical procedure without negatively affecting the final outcome," Parra says. He says that's one of the procedure's strong points. Since smaller tumors are less likely to have metastasized, patients don't lose valuable time trying the procedure if it proves unsatisfactory.

"Surgery is excellent for small renal cell carcinomas," Paz Fumagalli says. "It has a good track record for both safety and tumor control. But radiofrequency ablation is very promising. We may find out in certain patients it is as good or better than surgery when you factor in diminished kidney function and complications from surgery and anesthesia." He says results of clinical trials comparing long-term results from surgery with radiofrequency ablation are needed to ultimately prove how effective the procedure can be.

Meanwhile, he foresees combining approaches in some cases to benefit more patients. For example, if a patient had a small tumor with a bit of colon wrapped around it, the doctor could make an incision smaller than one required to remove a whole kidney and use a laparoscope to move the colon out of the way. Then the radiofrequency probe could safely be used to burn the tumor without damaging the colon.

Media contact: Erik Kaldor 904-953-2299 kaldor.erik@mayo.edu

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