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Zap Tumors

 
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10/06/2006 09:54 AM
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Zap Tumors
Tumor Zappers


Treating cancer with high heat offers new hope for patients. Hope, but not yet proof that it works.


Robert Langreth

Treating cancer with high heat offers new hope for patients. Hope, but not yet proof that it works.

Wisconsin schoolteacher Laura Mueller, then 53, was undergoing a routine checkup in 2001 when her primary-care physician spotted an 11-centimeter growth inside her pelvis. She was stunned to find out she had leiomyosarcoma, a rare cancer known for being resistant to drugs. Surgeons removed the tumor, but within six months the cancer had spread to her liver. After the drugs failed, her surgeons were reluctant to operate again. One doctor bluntly concluded, "This will probably kill you."

Mueller was sent to University of Wisconsin radiologist Fred T. Lee Jr., who offered her a new option: a procedure called radio-frequency ablation that kills a tumor by heating it to 140 degrees Fahrenheit and avoids the scars and recovery time of surgery. While not a cure, he said the technique might keep her disease under control. He cooked one liver tumor in August 2002, and in 2004 he and a colleague zapped three more small tumors in her liver and another in her lungs. Now Mueller has been in remission for 20 months. "I am ecstatic. I have been given a new life because of ablation," she says.

Drugs, radiation and surgery have long been the three arms of cancer treatment. Now radiologists are touting radio-wave zapping as a viable fourth weapon against smaller tumors. The method, still somewhat controversial, involves guiding a specialized needle into a tumor using precise ultrasound or CT imaging, then hitting it with roughly one ampere of radio current, just enough to fry it.

The procedure (including setup time) takes approximately an hour and can be done with minimal anesthesia; some doctors even send patients home the same day. Because it involves no cutting, it can be done on people too old or sick to withstand full-scale surgery. "We had a patient out kayaking the next day," says Bradford Wood, an interventional radiologist at the National Institutes of Health Clinical Center.

An estimated 40,000 tumor ablations (half in the U.S.) were done last year, with the number of procedures growing at a 15%-to-20% clip annually. Tyco Healthcare, Boston Scientific and tiny Rita Medical Systems make the equipment, which includes portable generators and single-use needles. Ablation is approved for inoperable liver tumors and painful bone tumors, and doctors are also testing it on kidney tumors, lung tumors and even breast cancers. Several companies are working on higher-power microwave tumor-zappers that may do the job faster.

Some of the radiologists who perform ablation procedures predict that it will eventually replace surgery for many small tumors. "We are in the beginning of what will be a huge new field of tumor ablation," says interventional radiologist Stephen Solomon at the Memorial Sloan-Kettering Cancer Center.

But other doctors, especially oncologists used to the rigorous standards of proof required for big drug trials, note a lack of controlled trial data showing that the procedure extends life. Because medical devices are regulated more loosely than drugs, the ablation devices were approved without anyone's having to affirm that they slowed cancer progression or increased survival above and beyond standard treatments. "The technology was invented on Tuesday, advertised on Wednesday, everyone took a course on Thursday and hung out a shingle on Monday," says Sloan-Kettering oncologist Leonard Saltz.

And unlike surgery, in which a tumor is removed and is then inspected by a pathologist, heat-zapping offers no immediate way to confirm that doctors "got it all." Blood vessels near tumors may disperse the heat, leaving some cancer cells unscathed. Saltz worries that some patients who might be cured by liver surgery are instead getting ablation treatments. A 418-patient M.D. Anderson Cancer Center study concluded that zapping was not as effective as surgery for colon tumors that spread to the liver. (The companies say they don't promote their equipment for operable cases.)

While ablation is generally safer than major surgery, serious--even fatal--complications can occur if the needle punctures or burns vital organs. Schoolteacher Mueller underwent corrective surgery and spent a week in the hospital when blood unexpectedly pooled around one of the ablation sites, partially collapsing a lung.

Joseph DeVivo, chief executive of Rita Medical Systems, whose shares languish just above $3, acknowledges the data dearth. "The biggest mistake of ablation was that there wasn't a big randomized study when the technology came out," he says. He does point to an uncontrolled study from the Cleveland Clinic, which found that colon patients whose liver tumors were ablated lived a median 29 months; this compares favorably to 20 months in the best drug trials. DeVivo says he can't afford more definitive studies. Combining drugs and ablation "is a one-two punch that should be the standard," he says, but convincing skeptical doctors "is the most frustrating job in the world."

Convincing patients is a bit easier. After his colon cancer spread to his liver in March 2004, Dublin, Ohio landscape architect John Reiner was told by doctors that almost two-thirds of his liver had to be surgically removed, pronto. He'd already had a large section of his colon removed. "The surgeon said 'We are going to cut you from armpit to armpit'" and promised a three-week hospital stay, he says. Not liking his odds, Reiner drove upstate to see the Cleveland Clinic's Allan Siperstein, who ablated the tumors with two radio-frequency procedures that required only overnight stays. Reiner has been cancer free for 18 months. "I don't know whether I would have made it through another big operation."

The concept of burning away tumors with electric current dates back a century, but it took modern imaging machines to make through-the-needle tumor-burning accurate enough to be safe and practical. John P. McGahan, a radiologist at UC, Davis, was one of the first to test the concept; he was inspired by the cauterizing tools surgeons use to close off blood vessels. In the late 1980s he got some calf's liver from a butcher and showed that radio energy through a needle could kill off all the tissue within a one-centimeter radius; he confirmed its potential in a small number of liver cancer patients also undergoing traditional surgery. Harvard doctors showed in 1992 that through-the-needle ablation could relieve excruciating pain from benign bone tumors.

The late 1990s saw the commercialization of fancier needles that could burn a wider radius. The latest models from Rita Medical and Boston Scientific contain umbrella-like tines that fold out from the main needle once it has been inserted into the tumor.

Unless ablation's backers can produce hard data showing how well it works, the procedure may continue to be a bit of an orphan. The best evidence now is in inoperable liver tumors that arise as complications of hepatitis or cirrhosis; ablation may keep these tough cases alive longer, a few studies show. But a far bigger market in the U.S. would be more common cancers, such as those of the colon that have spread to the liver, now treated mostly with drugs.

One trial comparing ablation plus drugs with drugs alone had to be scaled back after skeptical doctors refused to enroll patients; it is unlikely to yield definitive results. Boston Scientific hopes to settle the matter with a larger, 700-patient trial of advanced colon cancer patients set to begin later this year. Boston Scientific Vice President Scott Pisarczyk says: "We think drugs plus ablation will have a profound impact on survival and it is about time we prove it." Preliminary results could come in 2008.

Radio frequency ablation may help kill off small, inoperable tumors in the liver, kidney or elsewhere, with heat. Here is how it works:

1. A radiologist carefully guides an ablation needle into the center of a liver tumor using ultrasound or CT scans.

2. Some ablation needles have tines that deploy once the main needle is in place, in order to zap a larger area.

3. A generator sends radio-frequency current through the needle. The radio waves exit the tines and heat up nearby tissue.

4. The tumor cells heat up and die; most nearby healthy tissue is unharmed as the heat dissipates.

5. If the procedure is successful, only scar tissue is left. Doctors can repeat the ablation if needed.Subscribe to Forbes and Save.

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