RF ablation tops nonsurgical tumor treatment options

After four decades of experimenting with alternatives to surgical resection of tumors, researchers worldwide agree on several points: There is no silver bullet, but CT-guided radio-frequency ablation stands out among minimally-invasive therapies.

"Based on retrospective comparisons in matched patients, it is quite clear that in selected cases, such as cirrhotic patients with limited hepatocellular carcinoma, radio-frequency ablation can achieve the same or even better results compared with resection," said Dr. Riccardo Lencioni, a professor of diagnostic and interventional radiology at the University of Pisa, Italy.

Interventional radiologists on both sides of the Atlantic continue to debate what the preferred approach should be when surgery must be ruled out. Most, however, agree that RFA takes the lead in overall availability, cost-effectiveness, and efficacy.

RFA is the most widely used technique for ablation of focal liver lesions and the most powerful among percutaneous modalities when a single-needle electrode is used, said Dr. Luigi Solbiati, chief of radiology at the General Hospitals of Busto Arsizio, Italy. It can also be applied for ablation of kidney cancers, adrenal masses, lung cancers, bone lesions, and other tumors.

Alternative techniques, including percutaneous ethanol injection (PEI), microwave ablation, cryotherapy, and laser-induced thermotherapy (LITT), also vie for recognition in this arena, and for their own niches as well, according to Solbiati.

Cryoablation is slowly evolving from an intraoperative technique to a percutaneous option. Like RFA, its application is expanding from liver and kidney lesions, where it is known to be effective, into those affecting the lungs, bones, and spine. Unlike RFA, it is also considered relatively invasive.

Many studies have found that microwave ablation is faster than RFA and just as cost-effective and powerful, but it does not perform as well in small lesions. The same holds true for PEI, which is primarily employed for liver cancers when the other techniques are too expensive or not available. In many European countries, PEI is used not only for ablation of small hepatocellular carcinomas, but also for hyperfunctioning thyroid nodules, parathyroid tumors, and neck adenopathies from thyroid papillary cancer.

Recent studies in Germany have reported that LITT is useful to treat focal liver lesions using multiple fibers simultaneously, and it is effective in small lesions of the abdomen and the neck. But more trials are needed to validate findings, according to the authors.

Ultrasound, MRI, and CT all play roles in guiding various procedures. The preferred approach depends mainly on experience, real-time effectiveness, availability, and patient comfort.

"The best suited and the most widely used modality for guiding RFA procedures is CT, regardless of which organ is targeted," said Dr. Philippe L. Pereira, an associate professor of radiology at Eberhard Karls University in Tubingen, Germany.

Sonography is also reliable for needle placement but has visualization disadvantages, Pereira said. MRI-guided RFA offers multiplanar control, better tissue contrast, and near-real-time monitoring, but it is also time-consuming and more expensive than CT-guided RFA or cryoablation.

CT or ultrasound-guided RFA procedures are generally faster, but MRI-guided cryoablation provides a better visualization of the "icing" effect and can allow monitoring of the temperature of the organs, according to Dr. Eric vanSonnenberg, an interventional radiologist at Brigham and Women's Hospital.

"With CT or ultrasound, you know where the probe is, but you cannot actually see the effects of ablation on the tissue. MRI-guided cryoablation procedures are not widely available, however, and they are expensive," vanSonnenberg said.

Although most researchers agree that percutaneous thermal ablation techniques are cost-effective, no reliable data exist to support their superiority over surgical resection of tumors.

"There's been no controlled study to prove that assertion. Most of the studies have been done by individual centers, and none of them is randomized," said Dr. Gerald D. Dodd III, chief of radiology at the University of Texas, San Antonio.