Although a TSM strategy for treating HCC in early-stage, potentially curable HCC patients is likely to be common in real-world practice, its frequency and impact on outcomes is not well described. Our study reported a high rate of contraindications to PA (57.1%) in early-stage HCC patients who were ineligible for surgery. This is supported by other studies reporting similarly high rate of contraindications to PA (34–43%)[9, 11, 15], which further validates that our study findings are likely to reflect real-world practice. The two main contraindications to PA were difficult tumour location (47%) and large tumour size (> 3cm) (46%) in our study cohort. Our high rate of contraindications demonstrates the frequent technical limitations of PA therapy for early stage HCC in real-world practice, which is underappreciated in our view.
A subsequent problem related to this high rate of contraindications to PA is TSM to non-curative therapy. In this cohort, 57% of inoperable patients with early-stage HCC had TSM therapies. To the best of our knowledge, our study is the first to compare important oncological outcomes in this specific subgroup of surgically inoperable early-stage HCC patients who received the curative therapy (PA) versus patients who received non-curative TSM therapies as the initial treatment. The outcomes in those who received TSM were significantly poorer with lower OS, LTC and RFS. Although patients in the TSM group had a number of adverse clinical and tumour characteristics, the TSM group remained an independently associated variable for poor outcome (OS, LTC, RFS) when adjusted for other relevant clinical factors.
Another concerning finding from our study was the relatively high local recurrence rate for small HCC tumours treated with PA. Although PA is considered a curative therapy, we found that patients treated with PA had high rates of local recurrence at 1, 3, and 5 years (14%, 37% and 55% respectively). These high local recurrence rates could not be explained by poor selection as all tumours treated were ≤3 cm in maximal diameter, the standard accepted indication for PA treatment. Moreover, all interventional radiologists involved in the PA treatments for our study cohort were liver specialized and experienced with this technique. Although early randomised studies have reported better outcomes for local recurrence[16–18], we believe the local recurrence rates for PA reported in our study are more reflective of the real-world practice and are supported by a number of recent studies reporting similarly high local recurrence rates (23–54%) within 3 years[19–22]. The explanation for the high local recurrence after PA is unclear but likely relates to technical factors such as suboptimal tumour visibility under USS guidance during PA, challenging tumour location/ subphrenic region[20], leading to incomplete tumour ablation, or varying definitions of local failure of tumour control.
Taken together, these study findings demonstrate vulnerabilities associated with current HCC treatment algorithms using PA for surgically inoperable early-stage HCC, when implemented in real-world settings. Patients who are not eligible for surgical therapies are effectively placed in “double jeopardy” when referred for PA. The first risk they face is not being eligible for PA with subsequent migration of stage and treatment to non-curative therapies associated with poorer LTC and survival. The second risk they face is from the frequent failure after PA to provide effective LTC. The purpose of this paper is to highlight the limitations of PA within current algorithms in clinical practice, which in our view do not appear to be sufficiently recognized. These limitations suggest the need for randomized controlled trials of alternative, potentially curative treatments for inoperable patients with early-stage HCC. In our view, a leading candidate for such trials is SBRT. Recent non-randomized studies and systemic review investigating efficacy of SBRT in BCLC 0/A patients have suggested excellent LTC rates (> 90%) up to 3 years and equivalent OS in comparison to PA[8, 10, 13, 23, 24]. In addition, SBRT offers a number of other potential advantages including its ability to treat lesions in difficult locations (close to diaphragm, vessels and biliary structures) and lesions > 5 cm, and its non-invasive nature with no tumour seeding risk, and delivery in an outpatient setting[10,12,13,20].
There are several limitations of our study. Firstly, its retrospective and non-randomized design limits our ability to exclude selection bias, with differences in baseline clinical characteristics potentially explaining the poorer outcomes in the TSM group. To overcome this potential bias, we used a POM approach which allowed for estimation of marginal treatment effects rather the typical estimation of conditional treatment effects using a standard Cox regression approach. However, the potential for selection bias remains a possibility, to the extent that unobserved cofounders were not included in the model for treatment assignment. Despite this limitation, the ranges of the ATE’s were all within the range of biological plausibility. A further limitation was likely heterogeneity in the technical aspects of PA and TACE delivery and radiology reporting by multiple care providers across different centres. Nevertheless, this heterogeneity is reflective of real-world practice in many healthcare centres. Major study strengths include a large patient cohort and multicentre design. A further strength is that treatment allocation was by HCC multidisciplinary teams and according to current BCLC treatment algorithms.