High-frequency microwave ablation: a better fix for lung malignancies?

New high-frequency microwave ablation (MWA) technology with spatial energy control may be a better option than its conventional low-frequency counterpart in treating lung malignancies, reveals a retrospective study  published online October 20 in the American Journal of Roentgenology.

The researchers sought to evaluate the clinical performance of the new technology and to draw comparisons with low-frequency MWA treatment protocols. For the study, 59 consecutive patients underwent 71 sessions of high-frequency spatial energy-control MWA. The researchers then assessed several parameters, including technical success and efficacy of the technology, tumor diameter, tumor and ablation volumes, ablation time, output energy, complication rate, 90-day mortality, local tumor progression, ablative margin size, and ablation zone sphericity. '

This was followed by a retrospective comparison to data collected on a group of 56 patients, each of whom had been treated with 71 sessions of low-frequency microwave ablation. Statistical comparisons were performed using the Wilcoxon-Mann-Whitney test.

Both procedures were found to have a 98.6% technical success rate. Technical efficacy was similar, at 97.2% for high-frequency spatial energy control MWA and 95.8% for low frequency MWA, as was the 90-day mortality rate of 5.1% in the spatial energy-control MWA group and 5.4% in the low-frequency MWA group. There were zero intraprocedural deaths in either group.

The researchers noted more marked differences for other parameters, including median ablation time (8.0 minutes for high-frequency spatial energy-control MWA and 10.0 minutes for low-frequency MWA) and complications (in 21.1% of patients who had undergone high-frequency spatial energy-control MWA sessions and 31 percent of patients who had had low-frequency MWA treatments). Of these complications, 4.2% were major complications experienced by patients  in the high-frequency spatial energy-control MWA group and 9.9% were major complications experienced by patients in the low-frequency MWA group.

Additionally, the study revealed a lesser median deviation from ideal sphericity (1.0) in patients who had been treated with spatial energy control MWA than in those who had been treated with low-frequency MWA—at 0.195 and 0.376, respectively.  Absolute minimal ablative margins per ablation were 7.5 ± 3.6 mm in the former group of patients versus 4.2 ± 3.0 mm in the latter group. Patients in the high-frequency spatial energy control MWA group had a local tumor progression of 6.5% at 12 months. Differences in LTP rate and time point were deemed insignificant.

“High-frequency spatial energy control MWA technology and conventional low-frequency MWA technology are safe and effective for the treatment of lung malignancies independent of the MWA system used,” wrote lead authors Thomas J. Vogl, MD and Lajos M. Barsten, MD, of Frankfurt University Hospital in Frankfurt, Germany. “However, (high-frequency) spatial energy control MWA as an HF and high-energy MWA technique achieves ablation zones that are closer to an ideal sphere and… larger ablative margins than low-frequency MWA.”