Paula Moyer, MA

December 01, 2005

Dec. 1, 2005 (Chicago) -- Laser ablation with a neodymium:YAG (Nd:YAG) laser is as effective as surgical resection for the treatment of primary or metastatic liver tumors, according to a team of German investigators who presented their findings here at the 91st scientific assembly and annual meeting of the Radiological Society of North America.

A logistical advantage of Nd:YAG laser over other minimally invasive methods of tumor ablation is that it can be used with magnetic resonance (MR) guidance to enhance accurate delivery to the tumor site, according to the investigators. The current research focused on patients with colorectal liver metastases.

"Laser is as effective as surgery but with far less morbidity and mortality," principal investigator Martin Mack, MD, said during a press briefing. "The overall length of survival in this long-term study was 3.8 years after diagnosis, which is comparable to surgery, in which survival is 1.5 to 5 years." Dr. Mack is an associate professor of diagnostic and interventional radiology at the University of Frankfurt in Germany.

Dr. Mack and colleagues performed MR-guided laser-induced thermotherapy on 839 patients with 2,506 liver metastases of colorectal cancer. The patients were an average of 61.6 years old and were treated between 1993 and 2005. The laser wavelength was 1064 nm and was delivered continuously rather than pulsed.

Of these patients, 33.3% of the lesions were 2 cm or smaller in diameter. For these tumors, the average applied energy was 54.5 kJ. Another 33.3% were between 2 and 3 cm, to which the average applied energy was 94.9 kJ. The next tumor size, 3 to 4 cm, involved 18.1% of the lesions, and these received an average applied energy of 133.45 kJ. The remaining 15.6% of lesions were larger than 4 cm and received an average applied energy of 189.1 kJ.

Among the patients, 651 (77.6%) had 5 or fewer metastases and no extrahepatic disease at the time that they started treatment. These patients were treated with curative intention. The remaining 188 (22.4%) had more than 5 metastases at the liver or limited extrahepatic involvement, or both, and were treated with palliative intention. The number of metastatic sites treated was as follows: 1 site in 29.0% of patients, 2 sites in 26.5%, 3 sites in 17.8%, 4 sites in 10.6%, 5 sites in 7.5%, and more than 5 sites in 8.6% of the patients.

From the time of first treatment, average survival time was 3.3 years. The majority of patients (93%) were alive 1 year after treatment. At 2 years, 72% were alive, and at 3 years, 47% were alive. The 5-year survival rate was 24%. The average survival time in the curative group was 4.0 years; the palliative group survived an average of 2.8 years.

"This study is important in that it is a very large series of patients with a long-term follow-up to assess the overall results of laser-ablated therapy, and they reference it to the standard approach, which is surgical resection," said Richard C. Semelka, MD, in an interview seeking outside comment. "One of the critical aspects of the study is that patients had relatively short recovery times." These were typically one day.

"If you imagine that your survival will be 3.8 years following a procedure, having a one-day recovery has great advantages over a recovery of three weeks or more, because the shorter recovery enhances quality of life," Dr. Semelka said. "Minimally invasive techniques have great advantages in this regard." He is head of magnetic resonance imaging at the University of North Carolina in Chapel Hill, where he is vice chair of research and a professor of radiology.

Radiofrequency ablation,a commonly used minimally invasive treatment, cannot be performed with MR guidance, Dr. Semelka said. "MR is the most accurate imaging modality for finding even small tumors. It's best to find the full extent of malignant disease."

He noted that the study shows progress in the treatment of liver metastatic liver disease. "Even a few years back, this was a diagnosis of a terminal condition," Dr. Semelka said. "Now, with laser ablation and radioablation, metastatic liver disease is more of a chronic disease rather than a death sentence."

The next step in determining the utility for laser treatment of liver tumors is to compare it with another minimally invasive procedure, such as radiofrequency ablation, Dr. Semelka noted. "There may be compelling advantages if it has equal success," he said.

RSNA 91st Scientific Assembly and Annual Meeting: Abstract SSJ12-01. Presented Nov. 29, 2005.

Reviewed by Robert Chevrier, Site Editor/Program Director, Medscape Radiology.

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