Bass is living life after cancer with considerable energy and zeal. She runs her own travel business and serves as office manager for Hayakawa Sanki's busy San Antonio office. A self-described dynamo who "can't keep still," she's on the go day and night and travels around the world every few months. In April she visited Tokyo for three weeks on business. "You have to fight; you can't cry," she said.
"Each year about 100,000 people in the United States, like Ms. Bass, develop primary or secondary malignant liver tumors," Dr. Dodd said. "Traditional cancer therapies such as chemotherapy or radiation are ineffective in the treatment of these tumors. Surgical resection of the tumors is considered the only potentially curative therapy for these patients. Unfortunately, few patients are surgical candidates and of those who undergo surgery, 50 percent to 60 percent develop new liver tumors within one to five years.
"We need a new form of therapy that is minimally invasive, causes few side effects, and can be used repeatedly as necessary to treat recurrent tumors," Dr. Dodd added. "RF thermal ablation meets those requirements. It is anticipated that with ongoing refinements in this technology, it may soon become the treatment of choice for patients with liver tumors." Dr. Dodd recently presented the technique at the largest radiology meeting in the world, the annual conference of the Radiologic Society of North America.
Scientists this decade have developed several minimally invasive techniques to
treat liver tumors. These include cryotherapy (freezing), alcohol injection therapy, and
laser, microwave and radiofrequency heat ablation. "Of these, RF thermal ablation appears to be the most promising," Dr. Dodd said. "The treatment involves placing a needle through the skin and into a liver tumor. The needle is a special electrode through which a radiofrequency current is passed. The radiofrequency current heats the tumor around the tip of the needle and kills the tumor by cooking it. The procedure causes only minimal discomfort and can be performed without a general anesthetic."
Because healthy tissue can withstand greater heat than a liver tumor, physicians using RF thermal ablation are able to destroy a tumor and a small rim of tissue around its edges without affecting healthy liver tissue. The procedure requires an abdominal incision about 5 millimeters wide to accommodate entry of the needle. Patients usually are cleared to leave the hospital just a few hours after treatment.
Since Bass' procedure, another 35 patients have undergone one or more sessions of RF thermal ablation with Dr. Dodd. Of the first 75 patients treated in San Antonio, only one suffered a complication and many are tumor-free after their latest check-ups. Without treatment, they could have expected to live six to 12 months. Even after traditional surgical resection of liver tumors, only 30 percent of patients survive more than five years. "But RF thermal ablation currently is used only in patients for whom surgery is not an option," Dr. Dodd said. "For now, surgery is the treatment of choice."
RF thermal ablation must be further proven, agreed Bradford J. Wood, M.D., who, like Dr. Dodd, studies thermal ablation. Dr. Wood is an assistant professor in the Division of Interventional Radiology at the Georgetown University Health Science Center and a staff clinician in the Special Procedures Division, Department of Radiology, at the National Institutes of Health. "RF thermal ablation will be more widely available in the future--the initial, preliminary results certainly look good," Dr. Wood said. "But they are preliminary; there has been no randomized, prospective clinical trial of RF thermal ablation, and no long-term follow-up with patients. But intermediate and short-term follow-up data look very promising, mostly in the treatment of primary and metastatic liver tumors."
The NIH radiologist met Dr. Dodd in Boston a couple of years ago, when
Dr. Dodd gave an invited lecture at Massachusetts General Hospital.
"Dr. Dodd is certainly a well-respected researcher in this field, and continues to make a profound contribution in ultrasound-guided intervention," Dr. Wood said. "He undoubtedly will help us to determine the exact role that RF thermal ablation will play in oncologic [cancer] care."
Dr. Dodd, along with David L. Shepherd, M.D., assistant professor of
surgery in the Health Science Center's Division of Urology, plans to do a
research study of RF thermal ablation in patients with small renal cell
(kidney) carcinoma. Like the liver, the kidney is a large organ with healthy tissue surrounding most tumors. Today, surgeons generally remove the kidney and stop the cancer threat in nearly all patients with small renal cell carcinoma. "We want to study thermal ablation in patients who are going to have a kidney removed for renal cell carcinoma," Dr. Dodd said. "Since removal of a kidney is so effective at stopping renal cancer, we cannot suggest thermal ablation as an alternative to surgery until we see a 100 percent kill rate of tumors, by ablation, in these patients. But obviously, a viable alternative to losing a kidney is well worth exploring."
RF thermal ablation caught Dr. Dodd's interest several years ago. He first used the technique to ablate liver tumors in 1996, in collaboration with Glenn A. Halff, M.D., associate professor of surgery and director of organ transplantation programs at the Health Science Center. Most of Dr. Dodd's patients have been adults, but he has treated two teenagers, including one adolescent diagnosed with a gastric sarcoma, or cancer of the stomach, that had spread to the liver. The technique is only performed after cancer in other sites has been effectively treated with surgery and/or chemotherapy and radiation.
Manufacturers have introduced several models of the ablation equipment,
including the generator supplying radiofrequency current to the heated
needle. Previous models could eliminate tumors of 2.5 to 3 centimeters
(about 1 inch) in diameter, but Dr. Dodd's team is using a new-generation
needle that can destroy tumors up to 4 to 5 centimeters (almost 2 inches)
in diameter. "Our ability to treat larger tumors is
improving," he said. (See series of three illustrations above.)
RF thermal ablation of liver tumors was proposed as early as 1990 in the
United States and Italy, and the Italian doctors were the first to treat
liver cancer patients with the technique. Four major centers did the
bulk of the clinical work in this country. The Health Science Center and
Massachusetts General Hospital were the two primary U.S. centers to study
liver tumor ablation as a minimally invasive, outpatient procedure.
The University of California, San Francisco and the U. T. M. D. Anderson Cancer Center in Houston have studied it from a surgical, inpatient perspective.