To our knowledge, this is the first NMA to evaluate the clinical efficacy and safety of combining two combination regimens in patients with unresectable or locally advanced hepatocellular carcinoma as the first-line treatment[13, 14]. The VEGF antibodies included in our study were bevacizumab and ramucirumab, which target VEGF-A and VEGFR-2, respectively, and act by inhibiting the biological activity of human VEGF. However, TKIs participating in this NMA include sorafenib, lenvatinib and apatinib, whose targets include FGFR, PDGFR, KIT and the main target VEGFR. Although few studies were included in this study, the six included studies were all high-quality randomized controlled studies with a low risk of bias and similar baseline levels of patients. Sensitivity analysis assessed the robustness of the results and was broadly consistent with the main findings.
This study showed a certain tendency: anti-PD-1/L1 antibody combined with VEGF-antibody is the most effective therapeutic strategy in reducing the risk of death, while anti-PD-1/L1 antibody combined with VEGFR-TKI is more likely to bring longer PFS and higher ORR in patients at the cost of lower safety rate.
OS, as the primary endpoint of this NMA, provided the most objective clinical assessment of efficacy for indirect comparison. Unlike the ORR, it is not subject to differences in endpoint definition and does not suffer from the uncertainty of assessment across studies. The results showed that there was no significant difference in OS between the two groups, which was similar to the results of a recent retrospective study[15]. In our subgroup analysis, the clinical efficacy results were generally consistent with the primary results of patient analyses based on geographic region, ECOG score, and BCLC grade. Most notably, A + T was shown to have a significant advantage in patients with HCV, consistent with the results of a clinical study (mOS: 21 vs. 13 months, p = 0.043)[16]. There is no denying that the basic profile of the trial patients may also lead to erratic results. For example, ORIENT-32 only recruited patients in China, and the HBV infection rate was as high as 94%, while other trials recruited patients from different regions and had low HBV infection rates. Moreover, A + T shows a better ability to address MVI and EHS. Compared with those without MVI, HCC with MVI is usually characterized by worsening liver function, vulnerability to blood metastasis, a higher incidence of complications associated with portal hypertension and intolerance to treatment[17]. Patients with EHS usually have a poor prognosis, but the specific situation is closely related to the site of distant metastasis. Peritoneal metastasis and bile duct involvement in HCC patients treated with ICIs may indicate significantly poor OS but have no significant impact on the prognosis of ORR[18]. In a prospective trial using lenvatinib plus pembrolizumab, EHS was not an independent risk factor for OS, which may be related to front-line therapy in some patients[19]. Thus, we do not deny that the inadequacy of the included studies has contributed to the error in the results, so more high-quality trials should be promoted.
Different from the results of OS, A + T has a better effect in prolonging patients' PFS and reducing the size of solid tumours. The results are reproducible and have been demonstrated not only in vitro[20, 21], but also in clinical studies. A pilot study involving 10 HCC patients with vascular infiltration showed that after treatment with anti-PD-1 antibody combined with VEGFR-TKI, 7 patients achieved PR, 3 patients achieved CR, and all 10 patients underwent surgery with a recurrence-free survival rate of 75% within 12 months[22]. Another study also indicated that this conversion therapy strategy can be effective and safe for hepatectomy after careful preparation and patient evaluation[23]. At the same time, A + T combination treatment of renal cell carcinoma and non-small cell lung cancer also has an excellent tumour reduction effect with a high ORR[24, 25].
A + T showed higher toxicity with significantly higher incidences of all grade TRAEs and ≥ 3 TRAEs than A + A. As an important organ of drug metabolism, the liver is one of the most susceptible organs to cancer immunotherapy, and the liver damage caused by immunotherapy is often referred to as immune-mediated hepatitis (IMH) and often can be diagnosed by the increase in abnormally elevated serum liver enzymes[26]. Table 5 shows that the rate of abnormal elevation of serum liver enzymes in patients in the A + T group was higher than that in the A + A group. It can also be reflected that A + T can effectively improve the effect of immunotherapy. T cells may be overactive, which may lead to the destruction of immune tolerance in the liver, making it susceptible to acute inflammation and hepatitis[27, 28]. To control IMH, the guidelines recommend a detailed examination of the patient's liver condition prior to use of the drug, cessation of immunotherapy as soon as IMH occurs, and the use of corticosteroids as treatment agents[29–31].In the A + A group, the most common TRAEs were hypertension and proteinuria, which were closely related to the nephrotoxicity caused by VEGF antibodies[32, 33]. For the sake of patient safety, if patients suffer from complications such as diabetes or kidney disease, comprehensive renal function evaluation should be performed before A + A therapy, and patients’ hypertension must be well controlled[33].
This NMA also has limitations that need further consideration and exploration. First, the more complete the data presented in the report, the more robust the indirect comparisons, especially in the subgroup analysis. However, among the included trials, the data of two trials were obtained from the conference presentation, and the data were incomplete and possibly incorrect, which would eventually lead to the deviation of the estimation of the relative effect. In addition, the median follow-up time of each trial was different, which may have affected the final evaluation. In addition, the open-label nature of the trial was not an issue for survival endpoints OS but may have influenced other endpoints, such as ORR and TRAEs. Hence, more quality prospective studies are needed to better evaluate the optimal treatment. Second, a meta-analysis found that the Child‒Pugh score was subjective to a certain extent, and the ALBI score could better stratify patients[34]. Therefore, how to conduct more accurate stratification and precise treatment for patients before the implementation of treatment may be a major direction of our future research. Third, the results from a study in a mouse model of advanced HCC suggest that the use of high doses of sorafenib blocks VEGF signalling, leading to increased hypoxia and stromal cell derived Factor 1-mediated immunosuppressive cell recruitment and leading to drug resistance or reduced efficacy[35]. Therefore, determining the best dose or combination of drugs is also an area for further exploration. Last, because combination therapy may affect the pattern of tumour recurrence, we also focused on the effect of subsequent therapy. A recent study showed that discontinuation of atezolizumab plus bevacizumab in the absence of other therapeutic adjustments was associated with poor outcomes, including shorter OS and more AEs[36]. However, only 3 included studies described it, and TKIs played a major role (Leap-002: 34.9%, COSMIC-312: 14%, and CARES-310: 29.8%), which could not be compared. Thus, the search for the best follow-up regimen or drug use sequence will become an important challenge in the management of hepatocellular carcinoma.