Transarterial chemoembolization (TACE) is the standard treatment for Barcelona Clinic Liver Cancer (BCLC) intermediate-stage hepatocellular carcinoma (HCC) (1). However, in real-world clinical practice, the TACE procedure is not as easy to perform as we would expect. For some patients, the pattern of the blood vessels makes it difficult to place the catheter when carrying out TACE treatment. In this setting, no universal consensus for TACE treatment exists (2). More importantly, there is the severe problem of the refractoriness or unsuitability of TACE for patients with large and multifocal tumors (corresponding to lesions beyond up-to-seven criteria), when repeat TACE would be required. Beyond up-to-seven criteria means largest tumor diameter [in cm] + tumor number > 7. In theory, TACE increases tumor hypoxia and activates hypoxic response signaling, thereby inducing the upregulation of the vascular endothelial growth factor (VEGF) and the fibroblast growth factor (FGF), which can lead to tumor revascularization and progression (3). In addition, some HCCs do not show lipiodol uptake, which may result in the treatment being less effective (4). Therefore, complete response (CR) to TACE (especially for repeat TACE treatments) and good survival outcomes are hard to achieve for HCC cases at the higher substages of the intermediate stage (5). From intermediate-stage Substage 1 (B1) to intermediate-stage Substage 2 (B2), and even to intermediate-stage Substage 3 (B3), the reported median survival decreases remarkably (44.8 months, 21.5 months. and 11.3 months, respectively, p<0.001) (6). What is worse, after several TACE treatment sessions, some patients exhibit a deterioration in liver function (7). Statistically, liver function after both the third and fifth TACE sessions differed significantly from that after the first TACE session (first–third, p = 0.0020; first–fifth, p = 0.0008; third–fifth, p = 0.6145) (7).

Systemic therapy has been tried as a first-line treatment for intermediate-stage HCC, especially for larger (≥5 cm) or multiple lesions (mainly indicated for beyond up-to-seven HCC) (8, 9). Very recently, BCLC group have recommended systemic treatment rather than TACE treatment for the patient population with intermediate-stage BCLC with a high tumor burden [“diffuse, infiltrative, extensive HCC liver involvement” (10) and “large multifocal HCC involving both lobes” (11)]. Regarding systemic therapy, lenvatinib is a newly developed oral multi-tyrosine kinase inhibitor (TKI) that results in the dual inhibition of both the VEGF and FGF pathways (12). Based on the results of the REFLECT trial, lenvatinib has been widely approved as a first-line treatment for unresectable HCC in Japan, the United States, Europe, and other parts of Asia (13). Lenvatinib has exhibited favorable results in terms of inhibiting tumor angiogenesis and tumor growth (or in decreasing the size of the lesion) (14) and is more cost-effective than the current mainstay systemic therapy, sorafenib (15). Excitingly, in terms of intermediate-stage HCC, recent research with large multicenter randomized trials has consistently revealed the attractive survival advantage of lenvatinib over sorafenib and TACE treatment. The data showed that the median overall survival (OS) time for lenvatinib treatment was 13.6 months, while for sorafenib, it was 12.3 months (12); the median progression-free survival (PFS) time was 5.8, 3.2, and 2.4 months in the lenvatinib, sorafenib, and TACE groups, respectively (p <0.001) (16). The 6-, 12-, 18-, and 24-month cumulative survival rates in patients treated with lenvatinib were much higher than those in patients who received TACE treatment [p < 0.001) (17)]. Likewise, radiofrequency ablation (RFA), a standard therapy for early-stage HCC, was successfully tried for intermediate-stage HCC by some researchers (18, 19). Its beneficial survival effects were attributed to the complete destruction of the entire tumor. However, there were also problems. First, the thermal effect was considered to be weakened by the heat-sink phenomenon of inter- and peri-tumoral hypervascularity (19). Second, as a recent large-sample multicenter study pointed out, the survival benefit of RFA is limited to B1-and B2-HCC patients, not B3- and B4-HCC patients with poor liver function (20).

Inspired by recently published research on successful experiences and potential problems with the application of lenvatinib and RFA alone for the treatment of intermediate-stage HCC, we attempted to explore better therapy for Child–Pugh Class A (CP A) B2-HCC (characterized by a heavy tumor burden and relatively good liver function) other than TACE. In detail, we planned a retrospective study by introducing a combination of (first-line systemic treatment) lenvatinib and (sequential) RFA for CP A B2-HCC, with the belief that lenvatinib may decrease the vascularity and/or the size of the lesions and that would then RFA destroy the lesions, possibly to a curative degree. To evaluate the efficacy of this combination therapy more objectively, we used lenvatinib monotherapy as a control group. To date, the present study is the first to explore the efficacy and safety of lenvatinib plus RFA treatment for intermediate-stage HCC.

Our research specifically targeted HCC lesions with relatively good liver function but with a high tumor burden (B2-HCC). The treatment of these lesions is indefinite and problematic because the tumors are neither metastasized nor localized enough to make an obvious choice regarding recommended treatments (26). However, it is worth exploring the best therapeutic strategy for B2-HCC because those in this population are believed to be potential candidates for multiple or combination therapies, with a possible curative intent (26). To the best of our knowledge, our study is the first to combine RFA and lenvatinib for HCC, especially for intermediate-stage HCC treatment. As specific measures do not currently exist to estimate what dose or time-point should be set, or what efficacy and safety outcomes would be obtained from this combination therapy, especially for intermediate-stage patients who have mild hepatic impairment, our attempt was challenging. However, because of this, the promising results of our research will undoubtedly be a valuable reference for further clinical research and applications.

In our study, both groups yielded a high best tumor response value (ORR = 76.9% and 100% for the monotherapy and combination groups, respectively), which is in good agreement with previous studies on lenvatinib administration with a similar enrolled population to our study (intermediate-stage patients for whom the reported ORR was 61.3% (27) or 73.3% (8) in different studies). These results consistently demonstrate the effectiveness of lenvatinib for the treatment of intermediate-stage patients. Lenvatinib may inhibit multiple tumoral angiogenesis process, such as via blocking both the VEGF receptor and the FGF receptor, decreasing the circulating endothelial cells, and decreasing the levels of angiopoietin 2 (which is specific for lenvatinib rather than sorafenib) (13). When the vascularity of the lesions decreases, in theory, cancer cells are less likely to invade and metastasize through the bloodstream. When combined with treatments other than RFA (TACE, hepatic arterial infusion chemotherapy, sorafenib, regorafenib, etc.), lenvatinib has been reported to be a more favorable treatment option over TACE as a first-line treatment for intermediate-stage HCC (8).

In our study, a higher tumor response rate was observed in the combination group (the CR rate as the best response was 55.6% and the PR rate as the initial response was 66.7%) than in monotherapy group. In addition, a promising survival effect was shown in the combination group in terms of the 2-year OS (25.6% vs. 80% for the monotherapy vs. combination groups; p<0.001). Kim et al. (28) reported that for patients undergoing multiple-session TACE treatment, patients with CR or PR as the initial response or the best response had a relatively longer OS. In agreement with this finding, for intermediate-stage HCC patients with preserved liver function (a similar patient population to ours), Park et al. (29) found that both the initial and best responses during repeated TACE were significantly associated with OS. According to these viewpoints, tumor response and OS are closely related, and our good results regarding the tumor response may positively influence a favorable prognosis. Furthermore, RFA first positively affected the tumor response rates in the short term and, by improving the tumor response, had a good influence on the long-term survival prognosis for B2-HCC CP A patients when administered as an add-on treatment.

RFA was introduced for intermediate-stage HCC patients in our study, which was partially due to the multi-lesion characteristics of our target patient population. For multi-lesion cases, local ablation on the liver was believed to have a positive effect on distant HCC lesions. Eros et al. found that conducting RFA on one HCC lesion would suppress the growth of a co-existing distant tumor, as the distant tumor’s size decreased significantly (30). Recently, the synergistic effect of RFA and the systemic therapy drug sunitinib (tyrosine kinase inhibitors, equivalent to lenvatinib) was observed for the treatment of both HCC mice and patients (31). This combined treatment was confirmed to significantly increase the frequency of CD8+T cell, memory CD8+ T cell, and dendritic cells; decreased the frequency of regulatory T cells; and activated tumor-specific antigen immune response in the tumor microenvironment. According to this theory, the addition RFA treatment, as was the case in our study, could represent a plausible therapy for CP A B2-HCC rather than repeated used of lenvatinib alone. Excitingly, our study obtained many positive results that were obtained due to the addition of RFA. Firstly, the best response for all patients in the combination group were obtained after RFA treatment. Secondly, the combination group exhibited significantly better PFS and OS rates than the lenvatinib monotherapy group, regardless of the median value or 1-year and 2-year rates (p<0.05). More importantly, monotherapy (when compared with the combination treatment) was determined to be a risk factor for PFS.

One of the highlights of our research strategy is that we used lenvatinib as a first-line systemic treatment rather than a sequential treatment after RFA. We planned this procedure based on the following considerations: First of all, lenvatinib can inhibit HCC cell progression and proliferation by activating the FGF signaling pathways, which may reduce tumor size. Because of the reduction in lesion size, the tumor may be downstaged, facilitating the use of more curative treatments for early-stage HCC (27). RFA is widely acknowledged as the first-line curative option for unresectable BCLC early-stage HCC. Hence, the treatment strategy of lenvatinib followed by RFA may adhere to the international consensus to the fullest extent possible. Secondly, for intermediate-stage HCC, which characterized by large and/or multiple lesions, multi-needle and/or multi-site ablation would be required. Nevertheless, the multi-needle and/or multi-site ablation would increase the risk of surgical bleeding and surgical complications. Reducing the tumor’s blood supply and/or decreasing the size via lenvatinib treatment is undoubtedly advantageous for reducing the risks of the RFA operation and to achieve a sufficient ablative zone. It is worth mentioning that our original intention was to achieve the most curative treatment for HCC possible through our designed combination therapy. In terms of the encouraging tumor response results (100% ORR including 55.6% CR), which indicated cancer shrinkage or disappearance after treatment, we have achieved our curative intent.

In order to minimize AEs, we carefully set an appropriate time interval for the combination therapy in our experimental design. Pharmacokinetic analysis revealed that, generally, the terminal elimination half-life of plasma lenvatinib is approximately 28 hours (32). Lenvatinib is mostly metabolized in the liver. Unlike other types of solid tumors or in a healthy population, patients with HCC have a more or less reduced liver function that possibly decreases lenvatinib clearance, and HCC patients may not well tolerate lenvatinib at a higher plasma concentration (33). Out of a consideration for AEs that potentially accumulated during the combination treatment, lenvatinib administration was interrupted 4 days before RFA, the time-point of which was estimated based on the total clearance of plasma lenvatinib. Generally, serum AST and ALT levels, a reflection of the underlying liver metabolic burden, would be elevated when the hepatocytes are injured and become necrotic through various causes, such as hepatotoxic drugs (lenvatinib oral administration), and physical injury, including hyperthermia caused by RFA (34). Our study revealed that the majority of patients (88.9%, 8/9) in the combination group had elevated serum ALT and AST. What is worse, the incidence of a patient having an advanced ALT grade was much higher in the combination group (p=0.007). To avoid the cumulative liver injury AEs caused by lenvatinib and RFA, we specifically restarted lenvatinib treatment about 7–10 days after RFA (when the ALT and AST were supposed to decrease to almost normal levels). Fortunately, no serious AEs (over grade 3) presented themselves during the course of our study, which may indicate the safety of the combination therapy presented here. There were no statistical inter-group differences in the mALBI, nor any statistical differences before and after RFA treatment. As ALBI is a well-recognized and objective biomarker for hepatic reserve function (35), this result may suggest that additional RFA performance would not increase the risk of aggravated hepatic function.

The limitations of our study should be acknowledged. First, the patients were not randomly assigned to the combination and monotherapy groups during grouping. Only patients who were suitable and on whom it would be safe to perform RFA operation were included in the combination group. Seen from the opposite direction, however, this design was essential to ensure patient safety during the ablation procedure. To solve the problem of possible heterogeneity due to the non-randomized grouping, we recorded inter-group statistics regarding the baseline characteristics of the patients and lesions, and no differences were found. Second, the number of patients analyzed was small since it was difficult to enroll suitable CP A B2-HCC patients to receive our novel treatment. The small sample size might be the reason why we had a slightly shorter PFS (the median value of the monotherapy group was 5.5 months) compared to the published data from the REFLECT trial (the median value of PFS for lenvatinib was 7.4 months) (9). To overcome this problem, a large-scale study, preferably a multicenter study, would be valuable to prove our results.

In conclusion, our innovative combination treatment plan using first-line systemic lenvatinib therapy and subsequent RFA might be a potential option for patients in the intermediate stages of HCC with good liver function but a heavy tumor burden, as demonstrated by the better tumor response, improved rates of survival, and non-inferior safety when compared to the use of lenvatinib alone. Further clinical trials with longer follow-up periods and large-scale population are expected to confirm these findings in the near future.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by the Ethics Committee of Yokohama City University Medical Center (protocol code B210600051; date of approval: 9 June 2021). The ethics committee waived the requirement of written informed consent for participation.

Conceptualization, KN; methodology, SK; software, SMo; validation, HM; formal analysis, LR; investigation, KO; resources, AN; data curation, SMa; writing—original draft preparation, FW; writing—review and editing, FW and KN; visualization, MC; supervision, KS; project administration, SK; funding acquisition, n/a. All authors have read and agreed to the published version of the manuscript.

This research was supported by the National Natural Science Foundation of China (No. 82102074) Key Science and Technology Program of Shaanxi Province of China (No. 2022SF-320).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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