Curative in situ ablation of colorectal liver metastases-experimental and clinical implementation

In situ ablation of colorectal liver metastases is frequently assessed for palliative treatment only. The establishment of clinically relevant lesion size and a lack of long-term survival data were regarded as main limitations to using them with curative intention. In contrast to surgical liver resection, whose oncological findings seem to have remained unchanged over the years, the in situ ablation methods have considerably changed technically and clinically in the last few years.

The aim of the paper was to point out experimental and clinical data underlining the impact of in situ ablation for potentially curative treatment of colorectal liver metastases.

On the basis of experimental data, the aim of complete local tumor control (R0 ablation) can only be obtained if additional energy is applied after reaching the tumor-adapted maximal coagulation volume. Analogous to the oncological safety margin in surgical resection, we defined this decisive energy difference as the "energy safety margin" for in situ ablation. The energy safety margin is the energy that must be additionally applied after reaching the plateau in the energy/volume curve to achieve complete tumor coagulation. In addition to that, in situ ablation should be combined with temporary interruption of hepatic perfusion whenever possible to prevent intralesional recurrences. In this way, the thermoprotective mechanism of hepatic perfusion can be effectively eliminated. With restrictions, the survival data after ablation in specialized centers is comparable to surgical resection with concomitantly lower morbidity and mortality. Based on recent findings and with the corresponding expertise in the field of ablation and state-of-the-art equipment, ablation is, thus, an alternative to surgical resection. The combined application of surgical resection and ablation is also a suitable method for increasing the R0 rate and thus helps improve the prognosis of treated patients. In summary, it can be said that in situ ablation is a useful expansion of the therapeutic spectrum of liver metastases and can be applied as an alternative to or in combination with surgical resection.