Renal kidney cryoablation using CryoNeedles
Much like your air conditioner compresses Freon to cool, a procedure called SeedNet™ cryoblation compresses argon gas to freeze a kidney tumor to death. Earlier this year, Dr. Robert Barnett with Urology Associates was the first in Nashville to perform the procedure.
"The story on this is it's minimally invasive, and the patient does not have a general anesthesia," explains Barnett, who performs the procedure at Nashville's Baptist Hospital. "This is not done in an operating room. It's done in an X-ray suite with a CT scanner. The CT scanner is used to localize the kidney tumor and working in conjunction with an interventional radiologist … we use Dr. Webb Earthman here at the hospital … the needles are placed under local anesthesia through the skin and into the tumor."
While the SeedNet system has been used successfully for a couple of years for prostate cancer treatment, its use in battling kidney cancer is more recent. The procedure was developed by a Pennsylvania-based company called Oncura, which was created through the merger of two companies that specialized in the field of prostate cancer treatment. Barnett trains other physicians to use SeedNet for Oncura.
"Not all kidney tumors can be treated this way, but certainly a good number of them can be," he says. "Most of these tumors are small when they're found. Tumors up to about 3.5 centimeters, which is about an inch and a half in diameter, are amenable to this, as long as they're located in the kidney in a position that lets us put a needle in through the skin and directly into the tumor."
Barnett describes the needles as "small, thin knitting needles with a sharp point." Inside are two channels, one that allows the compressed gas into the needle and another where the gas expands, resulting in the cooling action. "As the argon gas expands, it gets very, very cold — about minus 190 degrees C — and the tips of these needles get very, very cold. With three or four needles in the tumor, we're able to drop the temperature of the tumor itself and some of the surrounding kidney to below minus 70 degrees C. Tissue cannot tolerate that kind of cold, especially if it's frozen and been allowed to thaw out and frozen again," he says.
Using two freeze-thaw cycles, the tumor and 2 to 3 millimeters of normal tissue around it are targeted. "We extend the freezing beyond what we perceive to be the edge of the tumor just to ensure that the whole thing is completely destroyed. If we lose a little rim of kidney, then that's quite acceptable and really has to be done to assure that the whole thing has been destroyed," he explains. "Over time, this area turns into a kind of a scar on the surface of the kidney, and problem solved."
The procedure takes one to two hours, and most of that time is spent positioning the three or four needles into the kidney. Patients spend the night in the hospital for observation. "They are literally back doing what they like to do. Now we won't let them go skydiving or bungee jumping the next day, but they can do whatever else they want to do," Barnett says.
The alternative to SeedNet and still the procedure necessary for some renal tumors is open surgery under general anesthesia followed by four or five days of hospitalization. "Especially if you're older and if you have comorbidities like diabetes, hypertension or overweight like a lot of America is these days, you're putting the patient at a lot more risk to solve the problem — and it's a serious problem, and it has to be solved," he adds.
While a biopsy is sometimes done at the time of the procedure, 98 percent of kidney tumors are malignant. Thus, physicians proceed based on that premise. "The likelihood of it being cancer is so extremely high that these things are all treated like they're malignant, and biopsies are not part of the evaluation," he says.
Barnett recalls an 80-year-old female patient earlier this year who had already lost one kidney and then half of the remaining kidney to cancer. The SeedNet procedure saved her remaining kidney function when another tumor appeared on the half kidney she had left. "Her kidney function stayed the same. She did not go on dialysis, and she's doing quite well. It really does offer another dimension in treating these things," he says.
A breakthrough like SeedNet is possible, Barnett notes, because somewhere between 40 and 60 percent of all kidney tumors are now found incidentally on CT scan or ultrasound because patients come in with bleeding or pain. "They aren't large tumors like we saw 30 years ago when we didn't have these diagnostic tests," he says.