Impact of Initial Therapy and Treatment Interval on Survival in Hepatocellular Carcinoma by Tumor Stage and Child–Pugh Class: Korean Primary Liver Cancer Registry Analysis

Technical Summary: Impact of Initial Therapy and Treatment Interval on Survival in Hepatocellular Carcinoma

Problem Statement
Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality, with curative treatments feasible in only approximately one-third of patients. While recurrence is common, necessitating subsequent therapies, the management of recurrent or residual disease presents a critical challenge. Repeated interventions can lead to progressive hepatic injury and functional decline, particularly in patients with underlying cirrhosis. Although tumor stage and hepatic function are established determinants of initial treatment selection, the impact of the timing between the first and second treatments on overall survival (OS) remains underexplored. Specifically, it is unclear whether the interval between treatments serves as an independent prognostic factor or merely reflects the durability of the initial therapeutic strategy across different tumor stages and Child–Pugh (CPC) classes.

Methodology
This study utilized a retrospective analysis of data from the Korean Primary Liver Cancer Registry (KPLCR), a nationally representative database covering approximately 15% of newly diagnosed primary liver cancer cases in South Korea. The study cohort included patients registered between 2008 and 2015.

• Cohorts: Two distinct analyses were performed. Analysis 1 included 9,156 patients to compare survival outcomes based on initial treatment modalities. Analysis 2 focused on 3,874 patients who received at least two treatments to evaluate the treatment interval.
• Stratification: Patients were stratified by tumor stage using both the Barcelona Clinic Liver Cancer (BCLC) system and the modified Union for International Cancer Control (mUICC) system, further categorized by CPC class (A, B, and C).
• Treatment Classification: Therapies were categorized into five modalities: Surgical therapy (resection and liver transplantation), Local ablative therapy (RFA, PEI, MWA), Locoregional therapy (TACE, TARE, radiotherapy), Systemic therapy (TKIs, immunotherapy), and Supportive care.
• Statistical Analysis: Overall survival (OS) was estimated using the Kaplan–Meier method with log-rank tests. Multivariate Cox proportional hazards regression was employed to identify independent prognostic factors, adjusting for demographic variables, liver function markers (e.g., albumin, bilirubin, ascites), tumor burden (size, number, invasion), and treatment modalities.

Key Contributions and Results

1. Survival Outcomes by Initial Treatment:
   Across most BCLC stages and CPC subgroups, surgical resection and local ablative therapies were associated with superior OS compared to locoregional and systemic therapies. In early-stage disease (BCLC 0–A, CPC–A), surgical therapy yielded the highest survival rates. In intermediate and advanced stages, while no significant differences were always observed between surgical and ablative therapies, locoregional therapies generally demonstrated better survival than systemic therapy or supportive care, though inferior to curative-intent treatments in specific strata.

2. Treatment Interval Patterns:
   A significant disparity in treatment intervals was observed based on the initial modality. Curative or near-curative treatments (resection, liver transplantation, and local ablative therapy) consistently resulted in longer intervals to the second treatment compared to non-curative approaches.

   • Median Intervals: Local ablative therapy showed the longest median interval (10.98 months), followed by surgical therapy/LT (8.98 months). In contrast, locoregional therapy had a median interval of 2.01 months, and systemic therapy had the shortest at 0.99 months.
   • Stage Consistency: This pattern persisted across all tumor stages; even in advanced disease (BCLC C), patients receiving resection or ablation had longer intervals (4–6 months) than those receiving locoregional (1–2 months) or systemic therapy.

3. Treatment Interval as an Independent Prognostic Factor:
   Multivariate analysis confirmed that the interval between the first and second treatments is an independent predictor of OS. A longer interval was significantly associated with improved survival (Hazard Ratio [HR] 0.981; 95% CI 0.975–0.986; p < 0.001). This association held true after adjusting for tumor burden, hepatic function, and treatment modalities. Other independent predictors of poor OS included larger tumor size, multiple tumors, vascular invasion, distant metastasis, and indicators of impaired liver function such as ascites and low albumin.

Significance and Claims
The authors posit that the first-to-second treatment interval serves as a clinically meaningful marker that integrates tumor biology, the durability of the initial therapeutic strategy, and the preservation of hepatic functional reserve.

• Prognostic Value: The study suggests that a shorter interval reflects more aggressive tumor biology, limited initial treatment durability, or rapid hepatic functional deterioration, all of which correlate with poorer survival. Conversely, a longer interval indicates a more favorable clinical course.
• Clinical Implications: The findings support the selection of initial treatment modalities that achieve durable disease control (e.g., surgical resection or local ablation where feasible) as a strategy to prolong treatment intervals and potentially improve clinical outcomes.
• Limitations and Scope: The authors explicitly note that the study does not establish a causal relationship between the interval and survival. They acknowledge that the interval is a composite marker influenced by heterogeneous clinical scenarios (e.g., incomplete response vs. recurrence) and that the retrospective nature of the registry data limits the ability to control for all confounding variables. Furthermore, the dataset (2008–2015) predates the widespread adoption of modern immunotherapy-based regimens (e.g., atezolizumab plus bevacizumab), which may affect the generalizability of the findings to current clinical practice.

In conclusion, the study identifies the treatment interval as a distinct prognostic parameter in HCC management, suggesting that the timing of subsequent therapy provides additional insight beyond conventional staging and liver function metrics.