Radio-frequency ablation expands imaging's role in cancer treatment

Radio-frequency ablation has achieved such impressive results in the treatment of unresectable liver cancer that researchers are testing the technique in other difficult-to-manage patients, such as those with lung cancer. In an ECR symposium on Monday morning, attendees learned that RF ablation is growing in importance for treatment of both lung and liver tumors. The role of radiologists is expanding to encompass not only diagnosis and treatment follow-up but also the management of cancer patients who cannot undergo surgery.

RF ablation seems well suited to the treatment of lung tumors because the air in adjacent normal parenchyma provides an insulating effect. Because of its high impedance, normally inflated lung tissue concentrates RF energy in tumors and limits widespread propagation of RF waves. It does, however, allow enough energy propagation to destroy at least a few millimeters of normal parenchyma and produce an ablation margin of safety around the tumor, said Prof. Riccardo Lencioni, a professor of diagnostic and interventional radiology at the University of Pisa, Italy.

Although surgical resection is the treatment of choice for patients with early-stage non-small cell lung cancer (NSCLC), only about 20% of patients have disease that is potentially curable by surgery. And patients with primary lung cancer are often poor surgical candidates because of coexisting chronic obstructive bronchopneumopathy or other associated disorders.

Conventional forms of treatment for these patients, such as chemotherapy and external-beam radiation therapy, have poor outcomes, with complete response rates as low as zero and three-year survival rates of 8%, Lencioni said.

"RF ablation could provide a valuable means for treating patients with early-stage NSCLC who cannot undergo surgery or who have recurrent tumors after surgery. RF treatment also may be combined with radiotherapy or chemotherapy in patients with more advanced primary tumors or for patients with certain types of metastases," he said.

Lencioni reported on experimental animal studies and preliminary results from clinical trials of RF ablation. In a multicenter study conducted at seven sites in Europe and the U.S., RF ablation achieved a technical success rate of nearly 100%; the electrode was correctly placed in 103 of 104 tumors. The study included 62 patients who had primary or metastatic lung tumors of 3.5 cm or less in diameter and who were not candidates for surgery.

Even more important, 93% of the tumors had stabilized or decreased in size and showed no signs of recurrence at six-month follow-up CT.

"The significance of these results is obvious if we consider that untreated tumors typically double over this time period," Lencioni said.

RF ablation has a longer and even more impressive history in the treatment of liver cancer. Prof. William Lees, director of the University College Centre for Medical Imaging at Middlesex Hospital in London, and his associates have reported studies from various investigators that showed complete ablation of 58% of primary liver tumors less than 3 cm in size. There was no recurrence in 67% of the tumors, most of which were less than 2 cm, and complete ablation was achieved in 75% of 44 liver metastases. In uncontrolled trials of patients with colorectal liver metastases, the procedure has achieved survival figures comparable to those of surgical resection.

Lees noted, however, that even with perfect RF ablation technique in the liver, almost half of patients will die from widespread disease. Of 109 patients with colorectal liver metastases treated with RF ablation at Middlesex Hospital since 1997, 39 have died, and 32 of those patients had uncontrolled liver disease. Another 17 died from uncontrollable local disease, and 15 of those patients presented with a lobular tumor pattern. Lees concluded that any treatment of such patients should consider the biological behavior of colorectal liver metastases.