Transcatheter arterial chemoembolization combined with simultaneous DynaCT-guided microwave ablation in the treatment of small hepatocellular carcinoma

Recent advances in image diagnostic technology and the widespread use of serological tests in high-risk populations have created potential opportunities for early clinical intervention in small hepatocellular carcinoma (SHCC) [1]. Although liver transplantation is still the ideal treatment for SHCC, only a small number of patients can receive this treatment [2‐4]. In contrast to liver transplantation, surgical resection is considered to be the first-line treatment for SHCC [5‐7]. Nevertheless, the risk of surgical resection for SHCC with multiple hepatic lobe lesions would undoubtedly increase. According to the Barcelona Clinical Liver Cancer (BCLC) guidelines, TACE is a palliative treatment modality. Of note, any single treatment has its own limitations and therefore, its efficacy may be limited [8]. In fact, Ablation (chemical or thermal) with TACE is established wherever the lipiodol deposition is incomplete and the lesion is targetable, and percutaneous acetic acid or ethanol injection is one of the important additional treatment options with TACE to improve outcome as it is cost effective [9‐12]. Furthermore, the researchers revealed that MWA has recently gained importance and acceptance due to better tumor control as compared to radiofrequency ablation (RFA) [8, 13, 14]. The purpose of our retrospective study was to analyze the safety and efficacy of TACE combined with simultaneous DynaCT guided MWA by comparing the patient group that received single treatment with TACE for SHCC.

The results of the present study demonstrated that the combination of TACE with DynaCT-guided MWA could improve local tumor control in SHCC. The PFS of the TACE-MWA group was significantly higher compared with that noted in the conventional TACE group. In addition, the combination group did not increase the incidence of postoperative complications compared with that noted in the group that received single treatment with TACE.

MWA is a thermal ablation method. In comparison with RFA, MWA uses electromagnetic energy to achieve higher temperature in a shorter period of time and to produce larger ablation areas [16‐19]. In a recent systematic review and meta-analysis, MWA was demonstrated to be as effective as RFA for HCC (OR 1.01, 95% CI 0.53–1.87, p = 0.98), and it provide superior outcomes compared with RFA in cases of larger nodules (OR 0.46, 95% CI 0.24–0.89, p = 0.02) [20] . Early studies have demonstrated the feasibility of TACE combined with MWA [21, 22]. A retrospective study of 244 HCC patients highlighted that the tumor response (CR + PR + SD) rates at 6 months was 92.1% in the TACE-MWA group compared with 46.3% noted in the conventional TACE (P < 0.001), and they concluded that patients with HCC tumors equal to or smaller than 5 cm in diameter (≤5 cm) exhibited a better response to combined treatment than that noted for TACE alone [23]. Additionally, the 1-, 3- and 5-year OS rates were significantly higher in the combination therapy group than those in the TACE alone group (p < 0.001) [24]. The mechanism of increased local tumor control that was noted in the combination group may be due to the complementarity of the two different therapies. Following TACE, the heat generated by the ablation needle could be concentrated in the lipiodol deposit, which could maximize the heat conduction effect of lipiodol and exert the maximum anti-tumor effect. In addition, the complex blood supply of certain irregular tumors led to uneven deposition of lipiodol. Therefore, MWA could target the ablation of residual tumor lesions and increase the rate of tumor necrosis. Furthermore, the use of MWA following lipiodol deposition can improve the transduction of heat to the peripheral tissues, thereby reducing recurrence and metastasis [25, 26].

Previous studies have suggested that the initial complete response represents an independent predictive factor for recurrence-free and disease-specific survival in patients undergoing ablation for HCC [24]. Moreover, the accurate placement of the ablation probes in the tumor targets is a crucial factor affecting HCC ablation [27]. Conventionally, sequential combination therapy is frequently adopted and ablation is usually performed 2–4 weeks following TACE under the guidance of computed tomography (CT) [14]. Recently, DynaCT employs cone-beam CT (CBCT) using the Artis zee DSA system (SIMENS, Germany) and allows for synchronized acquisition with flat-panel detector during C-arm rotation. And with the technique, TACE and MWA can be performed on the same working bed sequentially during one intervention. Following TACE, we now use DynaCT to scan the tumor and reconstruct 3D images for the puncture site and the route planning [28]. Wang et al. employed TACE combined with simultaneous CBCT -guided ablation to treat large HCCs in 21 patients, with a technical success rate of 100% [25]. In the study of Yuan et al., With precise guidance of CBCT, the ablation needle can accurately penetrate the target lesions of 46 patients and achieve favorable clinical results [29]. Therefore, DSA system with DynaCT allows for simultaneous combination of TACE and MWA in one intervention operation and more accurate puncture for ablation needles. And the synergism of these two benefits would further improve their therapeutic efficacy [30].

In the present study, the clinical effect of TACE combined with simultaneous DynaCT-guided MWA appeared superior to that caused by single application of TACE [31]. The progression-free survival of the combination treatment was significantly higher than that noted from single TACE treatment (P = 0.019). Following the combination treatment, the liver function of the patients was significantly altered and was gradually recovered to the preoperative level following 3 months of treatment, which was similar to the results reported by Andreano et al. [32]. Moreover, by adjusting the rack of the DynaCT machine, the time of patient transfer from the operating room to the CT room for MWA could be simplified, and the lipiodol deposition in the tumor tissue could be accurately displayed and recognized. This aided the decision making in the interventional procedures and resulted in improved safety of treatment by reducing the risk of operation.

Of note, the present study exhibits certain limitations. Initially, the sample size was relatively small that reduced the statistical power of the analysis. However, some of the results have already achieved the statistical significance. In addition, the short follow-up time period did not include the overall survival of the two groups and this may have led to biased results. It is also important to note that the process of puncture should be monitored continuously and may increase the radiation exposure of the clinician. Nevertheless, In order to minimize the side effects, we have tried to strictly monitor the radiation exposure time of clinician and patients, carefully evaluate the liver function reserve, and strive to improve the clinical prognosis of patients.

Our preliminary study showed that TACE combined with DynaCT-guided MWA was safe and effective for the treatment of SHCC. The immediate combined therapy can achieve satisfactory short-term outcomes and benefit SHCC patients. However, additional prospective studies are required to further clarify its effectiveness.