Radiofrequency (RF) thermal ablation is an encouraging new treatment option for patients with liver cancer. Recently Gerald D. Dodd, III, M.D., professor in the Health Science Center's Department of Radiology, permitted a Mission writer, art director and photographer to view the procedure in the radiology suite at University Hospital.
The patient's cancer had spread to the liver from the colon. In a separate operation, doctors had removed a large portion of his intestine. Now, several liver tumors needed to be ablated, or burned away. John Weaver, certified registered nurse anesthetist (C.R.N.A.) from the Health Science Center's Department of Anesthesiology, and Linda Hubbard, R.N., B.S.N., clinical research coordinator in the Department of Radiology, assisted Dr. Dodd.
Following several minutes of patient preparation and anesthesia, Dr. Dodd surveyed the liver by holding an ultrasound probe on the skin over the liver and viewing, on a computer screen, a host of images of the organ. Clicking a mouse and freezing the images, he marked the patient's tumors to chart where to place the slender heating needle used in RF thermal ablation.
The needle, or "ablater," is a special electrode through which a radiofrequency current is passed. Heat is produced around the needle tip, which is inserted directly into the liver tumor. The radio-frequency needle vibrates the tissue around its tip, producing frictional heat which "cooks" the tumor.
After making a small (5 milli-meter) incision in the skin overlying the liver, Dr. Dodd inserted a new-model ablater that actually contains three needles in a parallel triangular configuration (see illustration on page 4). The only active part of the device is the tip that measures 2.5 centimeters.
As Dr. Dodd instructed the patient to inhale and exhale, he used the ultrasound images to guide the needle through the liver and into the tumors. The needle electrode appeared as a bright line as it skewered the darker tumor. The clinical nurse, Hubbard, took notes and watched readings on the generator providing the radiofrequency current.
Before applying current directly to the liver tumors, chilled water was circulated through the needle. This was done to avoid charring the tumor tissue around the needle's tip. Charred tissue does not conduct the heat needed to ablate the remainder of the tumor, Dr. Dodd said.
"I'm getting warm," the patient said, prompting a reassuring "That's normal," from Dr. Dodd. Thermal ablation patients usually report a sensation of warmth in the abdominal area but with adequate anesthesia do not feel uncomfortable, he said. The needle reaches a temperature of 100 degrees Centigrade or 212 degrees Fahrenheit (the boiling point of water). "When we have ablated each tumor, we check the temperature of the tissue," Dr. Dodd said. "Although the tumor gets very hot, a patient's overall body temperature will not increase more than one degree during this procedure."
The patient was shielded from seeing the procedure. Thermal ablation of each liver tumor took about 12 minutes, and Dr. Dodd spent more than an hour treating four or five lesions in this patient. "The liver is ideal for this technique," Dr. Dodd said. "It is a large organ where tumors are likely to be encased by healthy tissue and where chance of bleeding from blood vessels, or other damage, is unlikely."
The needle insertion was about as invasive as a biopsy. Because it is well tolerated by patients, Dr. Dodd can repeat the procedure if tumors recur. "I've treated some patients seven times," he said. "We hope for a potential cure in one treatment, but we will treat again as many times as it takes to keep these tumors at bay."
Each outpatient treatment costs $3,000 to $4,000. Only about 100 of the
thermal ablation devices are currently in existence worldwide.