CT-guided percutaneous thermal ablation is a minimally invasive therapy to treat focal tumors by inducing irreversible cellular injury through the application of thermal energy, and MWA is one of the mainstream ablation methods. As a curative therapy for early-stage HCC, the primary purpose of ablation is to completely eradicate all viable malignant cells within the target HCC lesions . The treatment efficacy of ablation for relatively small HCC lesions is comparable to radical surgical resection [1, 2, 19]. The therapeutic scope of ablation can be extended by combining adjunctive methods such as TACE. TACE performed before thermal ablation could diminish the blood flow into the HCC lesions and lead to a larger ablation zone during the ablation procedure.
In our study, no significant difference was observed in LRFS and OS rate between GA and LA groups both before and after PSM. Local tumor recurrence could hamper the treatment efficacy of MWA greatly. Liver transplantation is by far the most effective therapy for liver cancer, patient selection has resulted in remarkable 10-year post-liver transplantation survival rates for HCC patients within Milan criteria . However, many HCC patients within Milan criteria dropped out while waiting for the transplanted liver source causing the progression disease. To receive increased allocation priority, HCC patients who are listed for liver transplantation are often treated while on the waiting list with loco-regional therapy (LRT) such as ablation and/or TACE . Moreover, complete response (CR) to LRT demonstrated in the first follow-up imaging study were more likely to undergo liver transplantation. All the patients enrolled in our study were within Milan criteria and all the patients achieved technical success and CR on the first follow-up enhanced MR. Our results demonstrated no significant difference in local tumor progression between GA and LA groups. This result indicated that both local anesthesia plus intraoperative sedation and general anesthesia are effective anesthesia modalities for CT-guided ablation in HCC patients within Milan criteria. However, the liver transplantation rate after combined therapy failed to record causing a short follow-up period and considerable censored data. Whether the anesthesia modality in the MWA procedure will affect the successful rate and therapeutic efficacy of following liver transplantation still need further investigation.
Local anesthesia combined with intravenous sedation is still the mainstay anesthesia modality for MWA, while general anesthesia also applied in some interventional therapy centers. Few studies focused on the comparison among different anesthesia methods in ablation procedure for hepatocellular carcinoma. The study of Lai et al.  suggested that treatment of small HCC with RFA under GA is associated with reducing the risk of cancer recurrence. Another study conducted by Wang et al.  demonstrated that applying GA in the thermal ablation of HCC patients could significantly improve the survival time of patients compared to LA. Some authors also argued that patients under LA suffered from pain and stress during the ablation procedure, thus leading to insufficient ablation zone . On the other hand, the study by Li et al. revealed that different anesthesia methods have no significant effect on treatment-related complications and LTP in HCC patients treated by MR-guided MWA . Whether the anesthesia modality would affect the therapeutic of percutaneous ablation in HCC patients is still in debate. In our study, no significant differences were observed in the LRFS and OS rate between the two different anesthesia modalities. This outcome is mainly due to the following reasons. First of all, most patients accepted local anesthesia plus sedation during the ablation procedure in our study could control their respiratory movement during needle insertion. To achieve a good therapeutic response to MWA, the precise insertion and placement of the ablation antenna are crucial. For patients who were unable to control their respiratory movement, multiple punctures were performed until the ablation antenna was inserted into the desired position. Secondly, TACE performed before MWA served as an adjunctive method, and the lipiodol deposited in the HCC lesions is a conspicuous marker during the MWA procedure. According to the lipiodol label, ablation antenna could be inserted through the center of HCC lesions in most cases regardless of the anesthesia modality. Moreover, TACE before MWA could diminish the blood flow into the lesions and enhance the power of thermal ablation, thus improving the treatment efficacy of the following MWA .
In the stratification analysis in LRFS of lesions, no significant differences were observed between different anesthesia modalities. HCC lesions in perivascular and/or subcapsular location were deemed as unfavorable location. Heat sinks effect were common for perivascular lesions, large vessels with higher flow could draw away heat from the ablative area. Theoretically, lesions in the perivascular location might be more beneficial from general anesthesia than local anesthesia during the ablation procedure. The possible reason for this discrepancy may be that HCC lesions enrolled in our study were all treated by MWA, and the MWA procedure could create high-temperature heating and lack of heat sink effects [26, 27]. Moreover, lipiodol deposited in the HCC lesions, as aforementioned, could diminish the hepatic artery inflow and reduce the “heat-sink” effect, thus enhancing the efficacy of subsequent ablation [25, 28].
Subcapsular location is challenging for percutaneous ablation due to the difficulty of accurate insertion of the ablation needle and obtaining enough ablative margin along the hepatic capsule. On the other hand, underlying thermal injury of adjacent structures for subcapsular lesions associated with a higher risk of major complications. No significant difference in LRFS between GA and LA groups for subcapsular lesions might attribute to the following reasons. In our study, artificial ascites was used, regardless of the anesthesia modality, to create hydrodissection for subcapsular lesions as appropriate . Consequently, treatment related complications were reduced while ablation efficacy improved. On the other hand, deposited lipiodol in HCC lesions enhanced the visibility of subcapsular lesions thus improving the accuracy of ablation antenna insertion .
There was no significant difference in the occurrence of treatment related AEs and complications before and after PSM. This result demonstrated that both general and local anesthesia were safe and feasible anesthesia modalities during the MWA procedure. As for cost analysis, the GA group presented a longer MWA procedure time, more healthcare providers participated, and more hospitalization costs. It is worth mentioning that both GA and LA groups have comparable hospital stays, and this may be attributed to no significant difference in the occurrence of treatment related AEs and complications. In this regard, general anesthesia is more costly compared to local anesthesia but showed a comparable treatment efficacy and safety.
There are several limitations in the present study. First, this was a single-center and retrospective study with an inevitable bias. Although propensity score-matching (PSM) was applied to diminish potential confounding and selection bias, there were still some heterogeneous between the two anesthesia groups. Second, the detail of the MWA procedure, such as the power and ablation time, were not recorded specifically. This drawback might hamper the rigor of the results in our study, as the parameters of the MWA procedure were critical for the therapeutic efficacy. Third, TACE performed before MWA may increase the rate of AEs and complications related to the MWA procedure. Last but not least, the limited follow-up period of the study may have impeded the thorough survival assessment of the patients. The long-term therapeutic outcomes of the two anesthesia groups during the MWA procedure need further investigation.
Overall, our retrospective study demonstrated no significant differences in the therapeutic outcomes between general anesthesia and local anesthesia plus sedation. Moreover, both the two-anesthesia modalities, during the MWA procedure, were safe and effective for HCC patients within Milan criteria. However, the cost in both procedure time, healthcare providers participated and hospitalization costs of general anesthesia was higher than local anesthesia. Thus, local anesthesia plus sedation may be more adaptive to CT-guided MWA in HCC patients within Milan criteria who received combination therapy for curative purpose.