Laser ablation with magnetic resonance (MR) guidance is as effective as surgical resection for the treatment of metastatic liver tumors, according to a team of German investigators who presented their findings here at the 91^st scientific assembly and annual meeting of the Radiological Society of North America (RSNA).

MR guidance -- which uses neodymium: YAG laser technology -- enhances accurate delivery to the tumor site, even to smaller lesions, the investigators said. Their research focused on patients with colorectal liver metastases, although the investigators hope that it can be used in the treatment of primary disease.

"Laser is as effective as surgery but with far less morbidity and mortality," said principal investigator Martin Mack, MD, Associate Professor of Diagnostic and Interventional Radiology, University of Frankfurt, Frankfurt, Germany.

He noted that 4% of patients die 30 days after liver resection, and that morbidity is increased in 30% to 405 of patients due to complications such as pleural effusion, compromised liver function, or bleeding, and can result in prolonged hospitalization.

"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," the researcher said during his presentation on November 29^th.

Dr. Mack and his co-investigators 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.

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

Results show that 77.6% of patients had five or fewer metastases and no extrahepatic disease at the start of treatment. These patients were treated with curative intention. The remaining 22.4% had more than five 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: one site in 29% of patients, two sites in 26.5%, three sites in 17.8%, four in 10.6%, five in 7.5%, and more than five in 8,6% of the patients.

From the time of the first treatment the average survival was 3.3 years. The vast 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 in the curative group was 4.0 years; the palliative group survived an average of 2.8 years.