Global research trends and foci of ablation therapies for liver tumours: a scientometric study

Abstract

Background

Ablation therapies have attracted sustained research interest in the management of liver tumours. This study aimed to systematically map global research trends, collaboration patterns, and the evolution of themes in liver tumour ablation using a scientometric approach.

Methods

Publications related to liver tumour ablation were retrieved from the Web of Science Core Collection. Scientometric analyses, including network construction, co-authorship analysis, and keyword co-occurrence and burst detection, were conducted using VOSviewer and Citespace.

Results

A total of 5,970 research articles between 1991 and 2022 were included. Publication output demonstrated continuous growth over the past three decades. The USA, China, Germany, Japan, and Italy were the most productive countries, with major contributions from institutions such as Sun Yat-sen University and Memorial Sloan Kettering Cancer Center. Authors and journal analyses revealed concentrated collaboration networks and diverse publication venues. Keyword analysis identified “hepatocellular carcinoma” and “radiofrequency ablation” as central research themes. In contrast, more recent research attention has shifted toward outcome-related and integrative topics, including overall survival, irreversible electroporation, and immunotherapy.

Conclusions

This scientometric study provides a data-driven overview of the global research landscape in liver tumour ablation, highlighting growth in publications, collaborative structures, and evolving research themes. The findings delineate emerging areas of scholarly attention and offer a structured foundation for future bibliometric investigations into research priorities and thematic development in this field.

Highlight box.

Key findings

• This scientometric study mapped the global research landscape of ablation therapies for liver tumours from 1991 to 2022, showing a sustained and rapid growth in publication output.

• Research activity is concentrated in a limited number of countries and institutions, with the USA and China as leading contributors and Sun Yat-sen University and Memorial Sloan Kettering Cancer Center as major hubs.

• Thematic evolution reveals a clear shift from technique-driven research (e.g., radiofrequency ablation) toward outcome-oriented and integrative topics, including overall survival, irreversible electroporation, cryoablation and immunotherapy.

What is known and what is new?

• Ablation therapies are an important and rapidly developing component of liver tumour management, with extensive clinical and technological research activity worldwide.

• This manuscript adds a systematic, data-driven mapping of collaboration networks, influential countries, institutions, and authors, and clearly documents the temporal evolution of research themes, identifying immunotherapy-related and combination-based strategies as emerging research frontiers.

What is the implication, and what should change now?

• The findings offer researchers a structured framework to understand the current landscape of liver tumour ablation research and to identify opportunities for collaboration and innovation.

• Future research should emphasize broader international cooperation and place greater focus on outcome-driven and combination-based approaches that integrate ablation with systemic and immunological therapies.

Introduction

Liver tumours, encompassing both primary liver cancer and secondary hepatic malignancies, represent a substantial global health challenge and a leading cause of cancer-related fatalities (1,2). Traditional treatment modalities, such as surgical resection and liver transplantation, have limitations, leaving a significant proportion of patients (more than 75%) with limited options due to factors such as locally advanced diseases, tumour size, location, or comorbidities such as underlying liver diseases (3,4). In recent years, the field of minimally invasive ablation therapies, including radiofrequency ablation (RFA), microwave ablation (MWA), and irreversible electroporation (IRE), has emerged as a promising alternative for the management of liver tumours in carefully selected patient cohorts (5-7).

Ablation therapy, a well-established and minimally invasive approach, utilizes image-guided techniques for the treatment of both primary and secondary liver cancers (8,9). Its advantages over conventional surgical interventions, such as reduced invasiveness, shorter hospital stays, and faster recovery times (10,11), have positioned it as a valuable treatment option, and its versatility allows for repeated procedures and combination with other treatment modalities, enhancing its utility in multidisciplinary liver tumour management (12,13). As the field of ablation therapy continues to evolve, gaining insights into the global research landscape, identifying key trends, and understanding the foci of investigation are of paramount importance.

Scientometric studies offer a systematic framework for analyzing scientific literature, providing valuable insights into publication patterns, identifying leading contributors, and uncovering emerging research themes (14). By employing scientometric analysis, this study aims to comprehensively assess the research trends and focal points of ablation therapy for liver tumours. This approach allows us to quantitatively visualize the current state of research, including contributions from countries, institutions, and authors, journal preferences, and emerging research directions. In particular, the co-word analysis of keywords within this field not only provides detailed information about subdisciplines but also reveals intrinsic associations among them, offering a holistic view of the evolving research landscape (15). The detection of co-existing keywords, or co-words, over time signifies emerging areas of interest that hold current and future significance (16).

While bibliometric analyses have been employed successfully to evaluate research trends in various medical disciplines and specialties, including gastric diseases, infectious diseases, and urinary diseases (17-19), an exploration of the literature trends within the context of ablation therapies for liver tumours has been notably absent. Our study aims to bridge this gap by employing bibliometric and scientometric analysis techniques, such as co-word matrix analysis and biclustering, to shed light on domestic research in the field of ablation therapy for liver cancer and its subdisciplines, track their recent evolution, and uncover future development trends. Through this comprehensive analysis, we aim to provide a foundational understanding of the global research landscape in liver tumour ablation therapies, stimulate international collaboration among researchers, and ultimately advance treatment strategies for liver tumours, thereby enhancing patient care. We present this article in accordance with the BIBLIO reporting checklist (available at https://jgo.amegroups.com/article/view/10.21037/jgo-2025-750/rc).

Methods

Data source, retrieval, extraction, and validation

The Web of Science (WOS) Core Collection was searched without imposing publication date restrictions, and the primary search was executed on September 30, 2022. An advanced search strategy was employed using the following keyword combinations: (“Ablation”) AND (“Cancer” or “Tumour” or “Neoplasm”) AND (“liver” or “hepatic”), with document type specified as “Article”. Inclusion criteria were: (I) publications explicitly related to ablation therapies for liver tumors; (II) studies addressing clinical applications, outcomes, technological advancements, or combination strategies involving ablation; and (III) articles published in peer-reviewed journals indexed in the WOS Core Collection. Exclusion criteria included non-English publications, conference abstracts, review articles, editorial materials, and records not related to liver tumors or ablation technologies.

The initial search yielded 11,678 records. After applying document-type filters and screening titles and abstracts for relevance, 5,970 original research articles were retained for analysis. All retained records were downloaded in plain text format with complete records and cited references. To ensure data accuracy and relevance, two authors independently screened and validated the retrieved records, paying particular attention to the titles and abstracts. Any discrepancies were resolved through discussion with a third author until consensus was reached. To assess the robustness of the search strategy and document-type filtering, the search was subsequently rerun using alternative spellings (e.g., “tumor” instead of “tumour”) and an updated cutoff date of December 31, 2022. These supplementary searches yielded higher overall record counts and article totals, reflecting spelling variants, database indexing updates, and differences in cutoff dates within the WOS Core Collection. Notably, the proportion of original research articles remained consistent across searches, supporting the validity and representativeness of the analytic dataset used in this study. All bibliometric analyses were conducted using the dataset downloaded on September 30, 2022.

Scientometric analysis tools and preprocessing

The validated dataset was imported into CiteSpace (Version 5.1.R3, Drexel University, USA) for bibliometric analysis. During data preprocessing, CiteSpace automatically identified and removed duplicate records based on bibliographic metadata, including title, author, and publication year (20). To visualize annual publication trends, GraphPad Prism 9.0 (USA) was employed. CiteSpace was employed to analyze publication characteristics, including countries/regions, institutions, authors, journals, and keywords (20), as well as to perform co-citation and citation burst analyses (using the burst-detection algorithm). VOSviewer (Version 1.6.16) and the online platform (http://bibliometric.com) were used to construct and analyze collaboration networks and keyword co-occurrence networks.

Co-authorship network analysis

Co-authorship data were extracted from the retained publications. Author names, institutional affiliations, and country/region information were recorded for each article. Collaboration relationships were defined based on co-authorship within the same publication. To improve network interpretability and reduce noise, minimum occurrence thresholds were applied at the country/region, institution, and author levels. For author-level analysis, a minimum threshold of 14 publications was used to identify core contributors. Network visualization and clustering were performed using VOSviewer, and collaboration strength was quantified using the total link strength (TLS) metric.

Keyword co-occurrence, clustering, and burst analysis

Keyword co-occurrence and clustering analyses were conducted using the “clustering” function in CiteSpace. Keyword clusters were generated using the Pathfinder algorithm and the log-likelihood ratio (LLR) method. Network quality was assessed using modularity (Q) and silhouette (S) scores; Q>0.3 indicates significant cluster structure, and S>0.7 indicates high cluster homogeneity. Citation burst detection was applied to identify emerging research topics. A time slice of four years was selected to balance temporal resolution and network stability over the long study period. The g-index (k=3) was used as the node selection criterion to limit the influence of highly cited nodes and reduce network complexity. Timezone visualization was used to illustrate the temporal evolution of research themes.

Country/region, institutional, journal, and citation analysis

Country/region- and institution-level collaboration analyses were performed using VOSviewer based on shared co-authorship. TLS values were used to quantify collaboration intensity. Journals were ranked according to publication volume, and citation and co-citation analyses were conducted to identify influential journals and articles within the field. Co-citation networks were visualized using CiteSpace and VOSviewer.

Statistical analysis

Descriptive statistical analyses were used to summarize publication characteristics, including annual publication output, country/region and institutional productivity, author contributions, journal distributions, and citation counts. Continuous variables are presented as counts, percentages, and trends over time. Linear regression analysis was performed using GraphPad Prism 9.0 (GraphPad Software, USA) to evaluate temporal trends in annual publication output, with the coefficient of determination (R²) used to assess goodness of fit. Bibliometric network analyses were conducted using CiteSpace (Version 5.1.R3, Drexel University, USA) and VOSviewer (Version 1.6.16). As this study is based on bibliometric and scientometric analyses of published literature, no inferential statistical comparisons between experimental groups were performed, and no hypothesis testing was required.

Results

Global publication trends

A total of 5,970 articles on liver tumour ablation published between 1991 and 2022 were included in the analysis. Annual publication output demonstrated a strong, sustained upward trend, with an average yearly publication volume of 186.56 articles (R²=0.9005; Figure 1). Three distinct developmental phases were identified: an early exploratory phase [1991–1996], a period of stable growth [1997–2002], and a rapid expansion phase beginning in 2003, marking a period of rapid expansion in liver tumour ablation research. Since the early 2000s, research output has increased steadily, reflecting the maturation of liver tumour ablation as a research field.

Figure 1.

Annual publication trends in liver tumour ablation research from 1991 to 2022. The figure shows the yearly number of publications retrieved from the Web of Science Core Collection. Linear regression analysis demonstrates a strong upward trend in publication output (R²=0.9005).

Contributing countries/regions analysis

A total of 82 countries or regions contributed to the liver tumour ablation research (Table 1). The USA ranked first in publication volume (1,741 articles; 28.9%), total citations (n=94,887), and number of collaborative links (n=55), followed by China, Germany, Japan, and Italy. The USA, China, and Germany also exhibited the highest TLS values of 894, 377, and 478, respectively, indicating extensive international collaboration. Although the UK and Italy produced fewer publications, they demonstrated comparatively high average citation rates (60.8 and 60.4 citations per document, respectively), indicating high average citation impact. Country/region collaboration mapping revealed three major international cooperation clusters, with dense collaborative ties among the USA, China, Germany, Italy, and Japan (Figure 2).

Table 1. Top 10 contributing countries/regions in liver tumour ablation research.

Rank	Country/region	Documents, n	Links	TLS	Total citations, n	Average citations
1	USA	1,741	55	894	94,887	54.5
2	China	1,327	37	377	29,344	22.1
3	Germany	619	41	478	19,406	31.4
4	Japan	542	31	224	23,106	42.6
5	Italy	466	48	453	28,168	60.4
6	France	348	44	366	18,614	53.5
7	England	298	43	388	18,105	60.8
8	South Korea	296	24	134	10,766	36.4
9	Netherlands	228	35	224	8,177	35.9
10	Taiwan	167	22	116	5,407	32.4

TLS, total link strength.

Figure 2.

Country/region collaboration network in liver tumour ablation research. Nodes represent countries or regions, and links represent international co-authorship relationships. Node size corresponds to publication volume, and link thickness reflects collaboration strength. Colors indicate major collaboration clusters identified by VOSviewer.

Contributing institutions

A total of 105 institutions contributed to the published literature on liver tumour ablation (Table 2). Sun Yat-sen University, Memorial Sloan Kettering Cancer Center, Fudan University, Chinese People’s Liberation Army General Hospital, and Sungkyunkwan University were the most productive institutions, contributing 158, 117, 91, 89, and 79 documents, respectively. Collaboration network analysis identified four major institutional clusters, with Sun Yat-sen University and Memorial Sloan Kettering Cancer Center serving as central hubs within their respective clusters (Figure 3). These findings indicate that research output is concentrated within a limited number of highly collaborative institutions.

Table 2. Top 10 contributing institutions/universities in liver tumour ablation research.

Rank	Institution, country	Documents, n	Links	TLS	Total citations, n	Average citations
1	Sun Yat-sen University, China	158	28	61	4,805	30.4
2	Memorial Sloan Kettering Cancer Center, USA	117	28	49	5,622	48.1
3	Fudan University, China	91	28	64	1,773	19.5
4	The Chinese People’s Liberation Army General Hospital, China	89	15	29	1,964	22.1
5	Sungkyunkwan University, South Korea	79	11	34	2,006	25.4
6	The University of Texas MD Anderson Cancer Center, USA	78	31	50	3,486	44.7
7	Harvard University, USA	74	14	36	6,872	92.9
8	University of Tokyo, Japan	72	15	63	5,316	73.8
9	University of Wisconsin, USA	66	11	15	3,930	59.5
10	Mayo Clinic, USA	64	35	55	6,475	101.2

TLS, total link strength.

Figure 3.

Institutional collaboration network in liver tumour ablation research. The network includes 105 institutions, with node size representing publication output and links indicating co-authorship relationships. Colors denote institutional collaboration clusters.

Contributing authors

Between 1991 and 2022, 29,260 authors contributed to liver tumour ablation research. In accordance with Price’s Law, a core group of 172 (Price’s Law square root =171.68) authors accounted for 50.7% (n=3,026) of all publications. The most prolific authors were Ping Liang, Jie Yu, Masatoshi Kudo, S. Nahum Goldberg, and Timothy M. Pawlik, who contributed 76, 53, 49, 45, and 45 articles, respectively (Table 3). Ping Liang and Jie Yu exhibited the highest TLS values of 226 and 185, respectively, indicating their central roles within collaborative author networks (Figure 4). Masatoshi Kudo had the highest number of total citations (n=3,071), indicating high citation impact within the field.

Table 3. Top 10 contributing authors in liver tumour ablation research.

Rank	Authors (surname, given name)	Documents, n	Links	TLS	Total citations, n	Average citations
1	Liang, Ping	76	11	226	1,768	23.3
2	Yu, Jie	53	11	185	768	14.5
3	Kudo, Masatoshi	49	10	82	3,071	62.7
4	Goldberg, S. Nahum	45	9	33	1,658	36.8
5	Pawlik, Timothy M.	45	7	32	3,041	67.6
6	Solomon, Stephen B.	44	12	125	2,000	45.5
7	Ricke, Jens	41	12	106	968	23.6
8	Sofocleous, Constantinos T.	38	12	133	1,843	48.5
9	Yu, Xiaoling	35	8	144	813	23.2
10	Cheng, Zhigang	31	9	145	399	12.9

TLS, total link strength.

Figure 4.

Author collaboration network in liver tumour ablation research. Nodes represent authors, with node size proportional to publication count and link thickness reflecting collaboration strength (total link strength).

Publishing journals and disciplinary distribution

Research on liver tumour ablation was disseminated across a wide range of journals (Table 4). The International Journal of Hyperthermia, Annals of Surgical Oncology, Journal of Vascular and Interventional Radiology, and Cardiovascular and Interventional Radiology were the most frequent publication venues. However, the top 10 journals collectively accounted for less than 20% of total publications. Dual-map overlay analysis demonstrated that liver tumour ablation research is primarily published within molecular, clinical, and health science journals (Z value =8.765), with citation linkages concentrated in pharmacology, biology, and health sciences (Figure 5).

Table 4. Top 10 journals with frequent publications in liver tumour ablation research.

Rank	Journal title	Countries	Documents, n	Number of all documents#, %	IF [2021]	JCR
1	International Journal of Hyperthermia	UK	169	2.83	4.112	Q2
2	Annals of Surgical Oncology	USA	114	1.91	4.978	Q1
3	Journal of Vascular and Interventional Radiology	USA	112	1.88	4.045	Q2
4	Cardiovascular and Interventional Radiology	USA	106	1.78	2.797	Q3
5	European Radiology	Germany	93	1.56	7.034	Q1
6	World Journal of Gastroenterology	USA	92	1.54	5.374	Q2
7	Radiology	USA	89	1.49	29.146	Q1
8	EJSO	UK	79	1.32	4.533	Q1
9	HPB	UK	78	1.31	4.465	Q1
10	PloS One	USA	73	1.22	4.069	Q2

^#, in the field of liver tumour ablation research. EJSO: European Journal of Surgical Oncology. HPB: the official journal of the international Hepato-Pancreato-Biliary association. IF, impact factor; JCR, journal citation reports.

Figure 5.

Dual-map overlay of citing journals (left) and cited journals (right) in liver tumour ablation research. Colored citation paths illustrate major disciplinary citation relationships. Ellipses represent journal clusters, with size proportional to publication volume.

Keyword analysis and thematic evolution

Keyword co-occurrence analysis identified “hepatocellular carcinoma” and “radiofrequency ablation” as the most frequent and central keywords within the research network, with counts of 1,086 and 810, respectively (Figure 6; Table 5). Keyword clustering analysis revealed 11 major thematic clusters, primarily focused on ablation techniques, treatment efficacy, survival outcomes, and adjunctive therapies (Figure 7, Table S1).

Figure 6.

Keyword co-occurrence network in liver tumour ablation research. Nodes represent keywords, with size proportional to frequency of occurrence. Links indicate co-occurrence relationships between keywords.

Table 5. Top 20 keywords of publications in liver tumour ablation research.

Rank	Keywords	Counts, n	Links	TLS	Year
1	Hepatocellular carcinoma	1,086	116	1,866	2010
2	Radiofrequency ablation	810	123	1,520	2013
3	Liver	312	107	708	1999
4	Liver metastases	293	93	564	2005
5	Colorectal cancer	290	89	618	1992
6	Ablation	258	106	640	2005
7	Liver cancer	256	94	393	1983
8	Microwave ablation	233	93	400	2000
9	Thermal ablation	192	90	351	1993
10	Survival	188	90	490	2004
11	Prognosis	136	61	289	2016
12	Liver metastasis	134	75	300	2014
13	Liver resection	128	65	268	2014
14	Hepatectomy	124	66	316	1997
15	Recurrence	124	72	325	1998
16	Radiofrequency	115	71	302	2009
17	Cancer	107	71	207	2013
18	Surgery	106	71	280	1994
19	Colorectal liver metastases	104	57	181	2014
20	Liver transplantation	102	69	262	2013

TLS, total link strength.

Figure 7.

Keyword clustering map based on co-occurrence analysis. Clusters were generated using the LLR algorithm, with colors representing distinct thematic clusters. LLR, log-likelihood ratio.

Temporal burst and Timezone analyses demonstrated a clear evolution in research focus over time. Early research was dominated by technique- and procedure-oriented keywords, including “radiofrequency ablation” and “cryoablation-related” terms. This was followed by a phase emphasizing clinical evaluation and procedural integration, such as imaging guidance, prognostic factors, and combined locoregional approaches. In recent years, outcome-oriented and integrative themes have emerged, including overall survival, IRE, and immunotherapy-related terms (Figures 8,9). Together, these patterns indicate a progressive shift from technique-driven to outcome-oriented and combination-focused research themes within the field.

Figure 8.

Top 30 keywords with the strongest citation bursts in liver tumour ablation research from 1991 to 2022. Red bars indicate periods of strong citation bursts, reflecting emerging research attention.

Figure 9.

Timezone visualization of keyword evolution in liver tumour ablation research. Keywords are arranged according to their first appearance, illustrating the temporal development of research themes.

Discussion

Ablation therapies are widely studied locoregional treatment approaches in liver tumours, prompting sustained research interest across clinical and translational domains (5-7). This Scientometric analysis provides an overview of the global research landscape in liver tumor ablation over the past three decades. The results reveal sustained growth in publication output, extensive international collaboration, and a clear evolution of research themes, reflecting the field’s progressive maturation from technical exploration toward more outcome-oriented and integrative research directions (21).

Temporal keyword and citation burst analyses indicate three broad phases in the development of liver tumour ablation research. Early studies were dominated by technique- and procedure-oriented keywords, including “radiofrequency ablation” and “cryoablation-related” terms, reflecting an initial focus on technological development. Subsequent research emphasized clinical evaluation, with increased attention to imaging guidance, prognostic factors, and treatment outcomes. In recent years, emerging keywords such as “overall survival”, “irreversible electroporation”, and “immunotherapy” have experienced intense citation bursts, indicating a shift in scholarly attention toward longer-term outcomes and combination-focused research. Importantly, these findings reflect changes in research focus rather than evidence of clinical efficacy.

Collaboration network analyses further demonstrate that liver tumour ablation research is characterized by a high degree of internationalization, with a relatively small number of countries/regions and institutions contributing disproportionately to the literature. Core contributors, including institutions such as Sun Yat-sen University and Memorial Sloan Kettering Cancer Center, occupy central positions within collaborative networks. This concentration highlights potential geographic and institutional imbalances and suggests that future research efforts may benefit from broader cross-regional and cross-institutional participation.

From a bibliometric perspective, the recent emergence of immunotherapy-related keywords represents one of the most prominent research frontiers in liver tumour ablation. Citation burst and Timezone analyses indicate that immunotherapy-related terms appear only in the most recent phase of the literature, distinguishing them from earlier technique- or procedure-focused topics. The increasing prominence of immunotherapy-related keywords likely reflects growing scholarly attention to combination-oriented research directions discussed in the broader basic and clinical literature (22-24). Nevertheless, bibliometric analysis does not assess underlying therapeutic mechanisms or clinical efficacy; rather, it delineates shifts in research focus and identifies areas of intensified academic exploration.

Several limitations should be acknowledged. This study relied on publications in the WOS Core Collection and included only English-language articles, potentially excluding relevant studies from other databases or languages. In addition, bibliometric indicators reflect patterns of research activity and citation behavior rather than direct clinical evidence. Despite these limitations, the present analysis provides a structured, data-driven overview of the evolution, collaboration patterns, and emerging themes in liver tumour ablation research. These insights may inform future bibliometric investigations and help contextualize ongoing developments within the broader oncology research landscape. Future bibliometric studies may further examine whether emerging themes—such as technological integration and earlier disease detection—translate into sustained shifts in research focus within liver tumour ablation.

Conclusions

In conclusion, this bibliometric analysis provides a structured overview of the global research landscape in liver tumour ablation over the past three decades. The findings demonstrate sustained growth in publication output, increasing international collaboration, and a clear evolution in research themes within the field. Analyses of collaboration networks and keyword patterns highlight the concentration of research activity among leading countries/regions and institutions, as well as the diversification and maturation of research topics over time. By identifying research gaps and emerging areas of scholarly attention, this study offers a data-driven foundation for further bibliometric and research trend analyses. Continued collaborative efforts and focused investigation may further advance understanding of research priorities and thematic developments in liver tumour ablation.

Supplementary

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Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.