Bibliometric analysis of global hodgkin lymphoma research from 2002 to 2022

Abstract

Background

Hodgkin lymphoma is a rare neoplasm of the lymphatic system, representing one of the most common cancers in young adults. It is characterised by a low number of malignant cells derived from B-lymphocytes and an extensive microenvironment.

Method

We used Scopus, Web of Science and PubMed databases with search descriptors; “Hodgkin* lymphoma“ and “Hodgkin* disease”. The common bibliometric indicators were applied.

Results

We retrieved a total of 18,304 articles within 2002 and 2022. The growth pattern showed a saturated pattern, with the linear and exponential plots coinciding. A small number of authors were responsible for the majority of the publications, with a transience index of 71.84%. The Bradford core consisted of 32 journals, with Leukemia and Lymphoma being at the top. The most productive institutions were resident in United States with the University of Texas MD Anderson Center at the helm. The United States was found to be the most productive country. Engert A. was the most productive author.

Conclusion

Scientific production in Hodgkin lymphoma was found to be saturated with a high transience index. This study provides a reference for oncologists, epidemiologists, funders, policy decision makers, academics, and Hodgkin lymphoma researchers.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12672-026-04560-w.

Background

Hematological malignancies refer to a group of neoplastic conditions of lymphoid and hematopoietic tissues which result in leukemia, lymphoma and myeloma [1]. Lymphoma is the most frequent solid tumor of hematological malignancies that originate from the lymph nodes and lymphoid tissues. Lymphoma can be further categorized into Hodgkin lymphoma (HL) and non – Hodgkin lymphoma (NHL) based on histological characteristics [2, 3].

Hodgkin lymphoma is a rare neoplasm of the lymphatic system, representing one of the most common cancers in young adults [4]. It is characterized by a low number of malignant cells derived from B-lymphocytes and an extensive inflammatory microenvironment [5]. Histopathologically, 95% of the HL cases are classified as classical Hodgkin lymphoma including the subtypes nodular sclerosing, mixed cellularity, lymphocyte-rich and lymphocyte-depleted HL. In the other 5% cases, nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is diagnosed [5, 6]. Classical Hodgkin lymphoma is characterized by the presence of CD30-expresssing Hodgkin and Reed-stern (HRS) cells surrounded by a variety of inflammatory cells. The malignant cells in NPLHL are termed lymphocyte predominant (LP) and are positive for CD20 and lack of CD 30 [5]. According to GLOBOCAN data for 2020, there were 83,087 new HL cases and 23,376 deaths, accounting for 0.45% and 0.23% of global cancer incidence and mortality, respectively. There were more cases and deaths occurring in males, and most (38.2%) of all cases occurred in Asia [7]. Epstein-Barr virus, certain genetic factors, and HIV have been described as independent risk factors [8, 9, 10]. Hodgkin lymphoma is a highly curable cancer with overall survival rate exceeding 98% in some populations [11].

Bibliometric studies are relevant tools in the social and scientific evaluation of a given discipline within a specified time frame. They serve as markers for activities in a given field of research, evaluate progress, and identify gaps in research [12, 13]. The performance analysis of selected study discipline is often via bibliometric and social network analysis. While biometric data computes the basis outputs, social network analysis interprets the influence of social links and interaction [14, 15]. Bibliometrics, through its indicators, focuses on calculation and analyzing the quantifiable values of scientific production. Bibliometrics comprises obtaining, processing, and managing quantitative bibliographic data from scientific publications.

The primary objective of this study was to analyze the state of scientific literature related to Hodgkin lymphoma that appeared from January 2002 to December 2022, in peer-reviewed journals indexed by Scopus, Web of Science, and Pubmed. We also wanted to assess productivity, publication, types, sites and trends in journal choice.

Methods

Data collection

We analyzed data on global Hodgkin lymphoma research in Scopus, Web of Science, and Pubmed published from January 1, 2022 to December 31, 2022. We performed the search on June 8, 2023. To retrieve the records, we made use of the descriptors “Hodgkin* lymphoma” and “Hodgkin* disease” linked by the Boolean operator OR in the title field. We retrieved all data under the above predefined search query without limitation on article types or language. The full details of the literature search and selection/screening are represented in Fig. 1. In accordance with the preferred Reporting items for Systematic Reviews and Meta-Analysis (PRISMA).

Fig. 1.

Flow chart for article extraction

Visualization of social network analysis

To visualize network analysis in Hodgkin lymphoma, we used VOSviewer (Center for Science and Technology Studies, Leiden University, The Netherlands) version 1.6.19 to map Hodgkin lymphoma research and collaborations.

Bibliometric indicators

Impact factor

We made use of Journal Citation Report (JCR) data of 2022. The Journal Impact Factor is a bibliometric indicator used as a measure of a journal influence. It was originally developed by the institute for Science Information (Philadelphia PA, USA). It is updated annually in the JCR of Clarivate Analytics.

Author/institution/country participation index

This refers to the number of documents on the subject topic contributed by an author/country or an institution. We evaluated the contribution of authors, institutions and countries in Hodgkin lymphoma-related research within the study period.

Co-authorship analysis

Co-authorship analysis refers to the interaction of authors contributing to a particular field/topic of study. It is a measure of collaboration [15]. We evaluated this using VOSviewer to show collaboration pattern in Hodgkin lymphoma research.

Keyword analysis

We made use of keyword analysis to show trends of discussion and view in Hodgkin lymphoma research.

Citation analysis

We used citation analysis to show the volume and pattern of citation in Hodgkin lymphoma research.

Price´s law

It is a broadly used indicator of productivity of a particular discipline or country. It uses exponential growth evaluation; to assess if scientific productivity in Hodgkin lymphoma follows Price´s law of exponential growth. We modeled the generated data into a linear adjustment according to the equation y = 8.6021x-16,529 and an exponential plot according to the equation y = 2E-50e^0.0605x. Price´s law is said to be fulfilled when the coefficient of determination of the exponential plot is greater than that of the linear plot [16].

Bradford´s law

We used Bradford´s law to determine the distribution and dispersion of scientific literature on Hodgkin lymphoma. Bradford proposed concentric zones of productivity termed Bradford zones, with decreasing density of information. He hypothesized each zone to contain similar number of documents. The postulated zones aid in identifying journals that are widely used in a specialized discipline. The stratification of journals in the different Bradford zones are viz.: 1, n, n²… [17]. The number of journals on the core and successive zones are expressed by the ratio as 1:n: n².

Lotka´s law

We used Lotka´s law (inverse square law) of scientific production to provide information on author´s distribution based on the number of publications. The law analyzes the publication volume of authors, expressing that a greater group contains authors publishing fewer than those publishing many. The law establishes that in the entire scientific community, the number of authors (A) who have published a number (n) of literatures in a period of several years of activity A(n) is equal to the number of those who have published a single literature A(1) in the same period, divided by the square of n. It is expressed mathematically as A(n) = a A(1)/n². According to this index, authors are divided into three levels; small producers (those who have published one article), medium-size producers (those who have published 2–9 articles), and large-scale producers (those who have published 10 or more articles) [18].

h, g- and p-index

We used the h-index to quantify the authors’ activity. It is often used to rate researchers’ performance. The g-index was introduced to measure the global citation performance of a set of articles and p-index which stems from the interrelationship between the two, and is calculated as its coefficient [19, 20, 21].

Statistical analysis

We used SPSS version 28.0 (SPSS, IBM) to evaluate the growth pattern of research output, linear and exponential regression adjustments. For the rest of the statistical graphs and tables, Microsoft Excel Software version 2021 (Microsoft Corporation, Redmond, WA, USA) was used. To fully corelate how countries expenditure on health and research and development relate to publication in Hodgkin disease, additional exploratory analysis was run on the most productive countries.

Result

Analysis of publication output

We retrieved 18,304 data after removing duplicate information. Of these, original research articles consisted 73.03%, followed by reviews (11.12%) and letters (7.04%) (Fig. 2). Language analysis showed that 87.56%, 3.70%, 1.67%, 1.64%, 1.50%, 1.46%, 0.72%, 0.69%, and 0.37% of the documents were in English, Chinese, French, Spanish, Russian, German, Polish, Japanese and Turkish language, respectively (Table 1).

Fig. 2.

Material types used in disseminating Hodgkin lymphoma related research outpu

Table 1.

Analysis of Language type used in HL-related research

Languages	Number of documents	%
English	16,027	87.56
Chinese	677	3.70
French	305	1.67
Spanish	301	1.64
Russian	275	1.50
German	268	1.46
Polish	132	0.72
Japanese	126	0.69
Turkish	68	0.37

Figure 3 shows the chronological distribution of scientific literature between January 1, 2002 to December 31, 2023. To evaluate whether the increase in scientific literature in Hodgkin lymphoma followed Price’s law, we fitted the obtained data linearly in accordance with the equation y=-0.2416x + 1357.6346 and the other fitted into exponential adjustment according to the equation y = 1577.5776e^{− 0.0003x}. The linear curve gave a correlation coefficient of 0.0009 while the exponential curve gave a coefficient of determination of 0.00011. As seen in the trend (Fig. 3), the mathematical fit to a linear curve and to an exponential curve coincide with practically no growth, except for a slight upturn in 2015. According to Price´s law [16], saturation point has been reached in this type of research. To further understand the trend of research before up to 1966 data, we made an extrapolative evolution plot (Fig. 4). This showed that there were linear and exponential growth until about 1992, where degrees of saturation set in.

Fig. 3.

Chronological distribution of Hodgkin lymphoma data within the studied period

Fig. 4.

Extrapolated evolution of HL research production

Analysis of proportion of articles by number of authors

From 2002 to 2022, there were a total of 61,240 authors that contributed to a total of 18,304 articles. This represents contribution rate of 3.45 authors per article. There were 223 articles in which the names of the authors were not available. Following Lotka´s law, we found that the smallest group is made up of authors with the greatest number of publications with more than 10 documents, who represents only 2.31% of the total productivity, while the small producers (authors with one publication) represented more than 70% of the total productivity (transience index of 71.84%). We analyzed collaboration index and found that the most common number of signatures with 10.9% is 4 authors per document.

Analysis of sources with the highest publication

Analysis of the retrieved articles based on Bradford zones shows that 32 journals (9.76%) made up the core zones, while 251 (19.51%) and 2,615 (70.75%) made up the zone 1 and zone 2 respectively. Only the core journals (32) produced 6,100 (33.33%) of scientific publications related to Hodgkin lymphoma within the study period.

We went further to stratify the 10 most productive journals among the core journals on Hodgkin lymphoma, with their respective impact factors, participation index, quartile, and position. All the journals have impact factors, with 9 and 4 of them having impact factors more than 3 and 10 respectively (Table 2).

Table 2.

Analysis of the 10 most productive journals on HL research

Source	No of documents	Productivity index	Impact factor *	Country of origin	Abbreviated Journal Title (ISO)	Category	Quartile	Position
Leukemia and Lymphoma	863	4,71	2,996	United Kingdom	Leuk. Lymphoma	HEMATOLOGY	Q3	53/78
Journal of Clinical Oncology	491	2,68	50,739	United States	J. Clin. Oncol.	ONCOLOGY	Q1	6/245
British Journal of Haematology	489	2,67	8,615	United Kingdom	Br. J. Haematol.	HEMATOLOGY	Q1	22/94
Blood	457	2,50	25,669	United States	Blood	HEMATOLOGY	Q1	3/94
Annals of Oncology	287	1,57	51,579	NETHERLANDS	Ann. Oncol.	ONCOLOGY	Q1	9/318
Annals of Hematology	251	1,37	4,030	United States	Ann. Hematol.	HEMATOLOGY	Q2	38/78
Haematologica	235	1,28	11,049	Italy	Haematologica	HEMATOLOGY	Q1	8/78
Cancer	170	0,93	6,921	United States	Cancer	ONCOLOGY	Q1	55/245
Bone Marrow Transplantation	168	0,92	5,174	United Kingdom	Bone Marrow Transplant.	HEMATOLOGY	Q1	23/94
Pediatric Blood and Cancer	164	0,90	3,838	United States	Pediatr. Blood Cancer	HEMATOLOGY	Q2	39/78

*2022 JCI Impact factor

Analysis of research area

Analysis of the various areas of research in HL showed medicine as the most studied area followed by Biochemistry, genetics and molecular biology. The full outlay of the various areas of study are shown in Fig. 5.

Fig. 5.

Analysis of research areas in HL

Analysis of productivity by countries

We analyzed the productivity in HL based on countries' participation index and found that 20 countries were responsible for more than 50% of all researches relating to HL (Fig. 6). We found the United States to be the most productive country, accounting for 28.62% of global research output relating to HL. This was followed by Germany (9.40%), Italy (8.75%), China (7.92%), the United Kingdom (6.48%) and France (6.41%) (Fig. 6). To further understand the association between participation index in HL related research and expenditure on research, we fitted a curve of productivity of research on HL and Current Health Expenditure (CHE) and Gross Domestic Expenditure on Research and Development (R&D) among the top 10 most productive countries. The trend of participation index was consistent with Current Health Expenditure, except for China and Italy which fell par. On the other hand, the trend on the participation index was found to be consistent with R&D except for Italy that was found lower and Japan that had higher expenditure value (Fig. 7).

Fig. 6.

Analysis of the 10 most productive countries

Fig. 7.

Relationship between production of scientific literature on HL and Current Health Expenditure (CHE) as% GDP, and Gross Domestic Expenditure on Research and Development (R&D), in the top 10 most productive countries in HL research

Analysis of the most productive institutions

Our analysis of productivity by institutions is represented in Table 3. We found the University of Texas MD Anderson Cancer Center to be the most productive (n = 570) institution in Hodgkin lymphoma-related research, with participation index of 2.79%. This is followed by Uniklinik Koln (n = 413; 2.26%), National Cancer Institute (n = 413; 2.26%), Memorial Sloan-Kettering Cancer Center (n = 411; 2.25%), Mayo Clinic (n = 386; 2.11%) and the others. Sixty percent (60%; n = 12) of the top most productive institutions are resident in the United States while two (10%) are resident each in Germany, Canada and France. The remaining 2 are resident in Italy and Sweden (5% each).

Table 3.

Analysis of 20 most productive institutions

Affiliation	Documents	PI*	Country
University of Texas MD Anderson Cancer Center	510	2,79	USA
Uniklinik Köln	413	2,26	Germany
National Cancer Institute NCI	413	2,26	USA
Memorial Sloan-Kettering Cancer Center	411	2,25	USA
Mayo Clinic	386	2,11	USA
Dana-Farber Cancer Institute	283	1,55	USA
British Columbia Cancer Agency	244	1,33	Canada
Universität zu Köln	242	1,32	Germany
National Institutes of Health NIH	225	1,23	USA
City of Hope National Med Center	220	1,20	USA
Fred Hutchinson Cancer Research Center	214	1,17	USA
Inserm	213	1,16	France
Harvard Medical School	209	1,14	USA
Institut de Cancerologie Gustave Roussy	202	1,10	France
University of Nebraska Medical Center	199	1,09	USA
IRCCS Centro Di Riferimento Oncologico Aviano	199	1,09	Italy
University of Toronto	195	1,07	Canada
Stanford University School of Medicine	193	1,05	USA
Brigham and Women’s Hospital	189	1,03	USA
Karolinska Institutet	177	0,97	Sweden

PI Participation index

Productivity of authors

Table 4 shows the 10 most productive authors. We observed that four of the 10 most productive authors are from the United States and are affiliated with the University of Texas MD Anderson Cancer Center Houston, Mayo Clinic, Brigham and Women´s Hospital, and the University of South California. Another set of four (4) are from Germany and are affiliated with the University of Cologne (Universitat zu Koln), the University Hospital Cologne (Uniklinik Koln), the Frankfurt Institute for Advanced Studies, and Goethe University, Frankfurt. The remaining two (2), were each affiliated with the University of Bologna, Italy, and Hôpital Saint Louis APHP, Université Paris 7, Paris, France. Engert A, Diehl V and Younes A were the most productive authors in HL-related research. We found that six (6) of the 10 most productive authors have h-index of more than 90, including one with 111. We also found two authors with p-index higher than 1.9, which indicated that they have highly cited articles.

Table 4.

Analysis of the top 10 most productive authors

Author	No documents	%	h-index	g-index	p-index	Country	Affiliation
Engert, A.	353	1.93	91	158	1.736	Germany	University of Cologne
Diehl, V.	188	1.03	96	180	1.875	Germany	University of Cologne
Younes, A.	164	0.90	86	163	1.895	USA	University of Texas MD Anderson Cancer Center
Borchmann, P.	154	0.84	55	107	1.945	Germany	University Hospital Cologne
Ansell, S.M.	144	0.79	96	166	1.729	USA	Mayo Clinic
Connors, J.M.	122	0.67	111	259	2.333	USA	Brigham and Women’s Hospital, Havard Medical School
Zinzani, P.L.	121	0.66	96	176	1.833	Italy	University of Bologna
Hansmann, M.L.	109	0.60	78	139	1.782	Germany	Frankfurt Institute for Advanced Studies+Goethe University
Cozen, W.	108	0.59	66	127	1.924	USA	Norris Comprehensive Cancer Center
Brice P.	94	0.51	72	138	1.1.969	France	Hôpital saint Louis APHP, Université Paris 7, Paris, France

Analysis of the most cited articles

We showed the top 10 most cited articles on HL research in Table 5. We found 5 of the articles to be original articles, 4 of them were clinical trials and 1 special recommendation. Five (5) of the top most cited articles were published open access while the other 5 were published toll access. The most cited Hl-related article is a clinical/special recommendation by Cheson, B.D. et al. in 2014 published in Journal of Clinical Oncology with 3,023 citations. The second most cited (2,732) article by Ansell, S.M. et al. 2015 in New England Journal of Medicine, also had the most citation per year as per articles devoted to HL research with an average of 390.9 citations per year, followed by the first most cited article with 377.9 citations per year (Table 5). More so, one (1) of the articles was published open access (in a toll access journal), another one (1), open access (in a hybrid journal), and another, open access (in purely open access journal). Five of the articles were published toll access with an embargo period, another two (2) toll access in a hybrid journal.

Table 5.

Analysis of the top 10 most cited articles on HL research

Title	Authors	Source title	Publication year	Total citations	PI (%)	Type of study	Publication type
Recommendations for initial evaluation, staging, and response assessment of hodgkin and non-hodgkin lymphoma: The lugano classification	Cheson, B.D. et al.	Journal of Clinical Oncology	2014	3,023	16.52	Special article	Open Access (In a toll acess journal)
PD-1 blockade with nivolumab in relapsed or refractory Hodgkin’s lymphoma	Ansell, S.M. et al.	New England Journal of Medicine	2015	2,732	14.93	Original article	Toll Access (with 6 months embargo)
Results of a pivotal phase II study of brentuximab vedotin for patients with relapsed or refractory Hodgkin’s lymphoma	Younes, A. et al.	Journal of Clinical Oncology	2012	1,204	6.58	Randomized clinical trial	Toll Access (with 12 months embargo)
Tumor-associated macrophages and survival in classic Hodgkin’s lymphoma	Steidl, C. et al.	New England Journal of Medicine	2010	1,022	5.58	Original article	Toll Access (with 6 months embargo)
Integrative analysis reveals selective 9p24.1 amplification, increased PD-1 ligand expression, and further induction via JAK2 in nodular sclerosing Hodgkin lymphoma and primary mediastinal large B-cell lymphoma	Green, M.R. et al.	Blood	2010	967	5.28	Original article	Open access (Hybrid journal)
Aggressive conventional chemotherapy compared with high-dose chemotherapy with autologous haemopoietic stem-cell transplantation for relapsed chemosensitive Hodgkin’s disease: A randomised trial	Schmitz, N. et al.	Lancet	2002	934	5.10	Original article	Toll acces (Hybrid journal)
Molecular diagnosis of primary mediastinal B cell lymphoma identifies a clinically favorable subgroup of diffuse large B cell lymphoma related to Hodgkin lymphoma	Rosenwald, A. et al.	Journal of Experimental Medicine	2003	919	5.02	Original article	Open access
Phase II study of the efficacy and safety of pembrolizumab for relapsed/refractory classic Hodgkin Lymphoma	Chen, R. et al.	Journal of Clinical Oncolog	2017	778	4.25	Clinical trial	Toll Access (with 12 months embargo)
Nivolumab for classical Hodgkin’s lymphoma after failure of both autologous stem-cell transplantation and brentuximab vedotin: a multicentre, multicohort, single-arm phase 2 trial.	Younes, A. et al.	The Lancet Oncology	2016	777	4.24	Clinical trial	Toll Access (Hybrid journal)
Early interim 2-[18 F]fluoro-2-deoxy-D-glucose positron emission tomography is prognostically superior to international prognostic score in advanced-stage Hodgkin’s lymphoma: A report from a joint Italian-Danish study	Gallamini, A. et al.	Journal of Clinical Oncology	2007	759	4.15	Clinical trial	Toll Access (with 12 months embargo)

Social network analysis (bibliometric mapping)

Inter-country collaboration network

We produced a bibliometric mapping of the research collaboration between countries involved in HL related research (Fig. 8) within the study period. The density of each circle (burble) represents the importance of each country. The figure showed 3 main clusters (red, blue, and green). The closeness between the burbles in each cluster indicates their relatedness, and establishes the number of co-authorships, and is measured by the thickness of the lines connecting them. The United States was found to be the country with the greatest density, and it is the focal point of the red cluster, made up of Japan, Turkey, India, South Korea and others. The second most dense cluster is the green cluster, made up of Germany, Netherlands, Denmark, Sweden, Switzerland and others, with Germany being the epicentre. The last cluster is the blue cluster consisting of Italy (epicenter), France, Spain, Canada and others.

Fig. 8.

Inter-country collaboration network

Network of collaboration between institutions

We mapped the collaboration relationship between institutions (Fig. 9). The mapping revealed 10 major clusters (red, blue, turquoise, purple, green, golden lemon, orange, pink, sky blue and light blue). The most dense collaborations were the red, blue and lemon clusters. While Mayo Clinic and Memorial Sloan Kettering Cancer represented the epicentres of the red cluster, Brigham and Women Hospital and North Carolina Cancer Center represented the epicentres of the blue clusters. The Fred Hutchinson Cancer Research Center and the University of Iowa represented the epicenters of the lemon cluster.

Fig. 9.

Network analysis of collaboration between institutions

Network of authors collaboration

The visualisation of the network of author collaboration is represented in Fig. 10. The author collaboration network shows 7 major clusters (blue, green, red, purple, golden lemon, turquoise, and brown). The blue cluster was found to be the most dense network and was dominated by Engert A., Diehl V., and Borchmann P., who are also among the top most productive authors in HL related research. Next is the golden lemon cluster dominated by Zhang Y. and Cerhan JR. Though Zhang Y, unlike Cerhan JR was not among the top 10 most productive authors. Next on the sequence is the red cluster which is dominated by Conors JM. Both authors were among the top 10 most productive authors on HL related research. The purple, brown and turquoise clusters are dominated by Younce A, Ansell SM and Wang Y, respectively. Though Ansell SM was among the top 10 most productive authors, the network cluster (brown) density is low. There was virtually poor network of collaboration among authors in the turquoise cluster. Further visualization of the authors’ collaboration using the overlay visualization mode of VOSviewer (Figure S1) showed the evolution of the importance of authors within the time frame. While old authors played a major role within 2008 were coloured in dark purple. authors such as Engert A, Younes A were major players within the time period of 2012 to 2014. On the other hand, authors such as Borchmann P, Zhang Y, Fuchs M etc. are more contemporary players on HL-related research.

Fig. 10.

Network of author collaboration

Keyword analysis

In the keyword analysis, we excluded human, article, priority journal and Hodgkin disease (since it is among the keywords used in the query). The keyword analysis showed 3 broad clusters (Red, green, and blue). The largest cluster is the red cluster which majorly represented treatment option for HL. These include words such as doxorubicin, cyclophosphamide, vincristine, antineoplastic agents, prednisone, bleomysin, etoposide, vinblastine and rituximab. The second largest cluster is the green cluster which represented demographic data related keywords. These includes words such as adult, male, female, middle aged prognosis, survival rate, adolescence, age, child and a follow up. The last cluster is the blue cluster which represented the study design and diagnostic methods. The major keywords here are controlled study, case report, clinical article, immunohistochemistry, histopathology, protein expression, human tissue, clinical features, computer assisted tomography, pathology. Words with over 10,000 total link strength and over 5,000 occurrences are male, female, adult, aged, aged (in the green cluster) and doxorubicin (in the red cluster) (Fig. 11a). We further applied the overlay visualisation mode of VosViewer to reveal the evolution of the keywords over the years (Fig. 11b). The overlay visualisation showed “Progression free survival” and “antineoplastic combined chemotherapy” standing out in recent years as current discussions in HL-related research. This implies the shift of focus from new therapeutic approach to combination of existing ones as well as survival analysis of such chemotherapies.

Fig. 11.

a Network visualization of keyword occurrence. b Overlay visualization of keywords according to year

Citation network analysis

Analysis of author citation network

The author citation network of the participating authors are presented in Fig. 12. The citation network among the authors showed three (3) distinct clusters; red, blue and green. Each cluster is formed by a set of authors who cited each other’s work more frequently, painting an image of colleagues from single institution that shape a greater ideological similarity. As central nodes within the network, Connors JM (red cluster), Diehl V (red cluster) and Engert A appear strongly connected with other clusters.

Fig. 12.

Analysis of authors citation network

Analysis of citation network by country

The citation analysis based on country is represented in Fig. 13. The citation distribution is represented in three clusters: red, blue and green. Citation preponderance was observed in authors from the United States. Authors from the United States (red cluster), Italy (blue cluster), France (blue cluster) and Germany (green cluster) formed the core of the citation network, and had the highest citations network. Authors from the United States appear to have the highest citation link strength with German authors, followed by French authors. The trend shows that articles published in these countries were widely cited.

Fig. 13.

Analysis of country citation network

Institutional citations network analysis

Institutional citation network is presented in Fig. 14. The core institutions amassing citation in HL research are Mayo Clinic, Memorial Sloan-Kettering Cancer Center, University of Texas, Washington University and University of Rochester, and Rosewell park Cancer Institute.

Fig. 14.

Analysis of institutional citation network

Bibliographic coupling

Bibliographic coupling/linkage, like co-citations is a measure of similarity that uses citation analysis to establish a similarity relationship between papers. Bibliographic coupling occurs when two papers reference a third common paper in their bibliographies [22]. It is commonly used to identify cohort of studies that are thematically related [22]. On the other hand, co-citations occur when two authors are jointly cited in a third publication. In other words, while bibliographic coupling identifies authors that have a comparable “knowledge base”, co-citation profiles cluster of authors whose publications have similar “impact” [22].

Bibliographic coupling/linkage of authors

In bibliographic linkage of authors, node sizes are proportional to the number of the documents of the respective authors. Similarity in cluster colour for authors implies the degree of overlap between the reference lists of publications of these authors is higher [23]. The bibliometric coupling of this study (Fig. 15) shows five (5) clusters (red, blue, green, purple, and lemon clusters) of closely coupled authors to reflect shared thematic focus. Authors with the largest number of Hodgkin lymphoma articles in the green clusters are Kwee TC, and Ansell SM. In the red cluster, Adams HJA and Straus DJ had the largest number of HL articles to their name. Ansell SM displayed the strongest coupling link strength.

Fig. 15.

Bibliographic coupling of authors

Bibliographic coupling of countries

Figure 16 shows the bibliographic coupling of the topmost productive countries. The result showed 6 closely related clusters; red, blue, green, lemon, sky blue, and purple. Among the red cluster, the United States showed the highest strength in terms of contribution, followed by China, India, and Japan. Among the green clusters, Germany, followed by the Netherlands showed the highest coupling strength. Italy and Israel showed highest contribution among the Lemon cluster. On the other hand, the United Kingdom and Spain had the highest contribution in the blue cluster. Canada was the sole major contributor in the light blue cluster. The thickness of the links depicts the degree of intersection of the literature between the different countries [23].

Fig. 16.

Bibliographic coupling of countries

Discussion

We observed the most utilized document type in this study to be original articles, constituting 73.03% of all the literature in the study repertoire. This observation fortifies the fact that the subject matter resides with clinical research or experiment.

We observed a saturated research trend in Hodgkin lymphoma research in this study. This trend is at variance with the exponential growth study trend observed in sickle cell disease research [13], optometry [24], and linear growth trend reported in Lassa fever research [12]. The reason for this saturation may be multifaceted. First, as major questions in HL research are answered, the remaining research may involve more complex, nuanced issues that yield fewer publications per unit of research effort, thus, slowing down the pace of publication. Secondly, funding and research efforts might shift towards other areas with emerging or more pressing questions.

We observed a high transience index of 71.84%. This is a reflection of the high rate of occasional publishers who specialized in other related areas but sporadically publish on HL related research. We only identified 2.31% of the authors as heavy publishers. This portrays that the large proportion of scientific literatures as relates to HL research originated from a few numbers of researchers.

The Bradford analysis of the studied literature showed that 32 journals (9.76%) were responsible for 33.3% of the entire scientific production of HL research. This trend echoes the concentration of scientific literature on a small number of journals. Of these top journals, Leukaemia and Lymphoma had the highest number of publications (863), accounting for 4.71% of all HL research, followed by the Journal of Clinical Oncology (n = 491; 2.68%), and the British Journal of Haematology (n = 489; 2.67%). All the top 10 journals were dedicated to either hematology or cancer. These journals are potential niche for future dissemination of breakthroughs in Hodgkin lymphoma- related research.

Analysis of productivity by country showed the United States dominated HL-related research output, followed by Germany, Italy, China, the United Kingdom and France. The United States alone accounted for 28.62% (n = 5238) of all HL-related research output. The reason for this marginally high productivity may not be far-fetched. United States houses Seagen Pharmaceutical (now part of Pfitzer), that collaborates with Takeda Pharmaceuticals to manufacture Brentuximab vedotin used in management of Hodgkin lymphoma. Also niched in the United States are Pfizer Inc. that manufacture Dacarbazine, Adriamycin (Doxorubicin hydrochloride), vincristine sulfate; MERCK Pharmaceutical that manufacture Keytruda (Pembrolizumab); Baxter, that manufactures Doxorubicin hydrochloride. This finding is consistent with previous studies in other biomedical researches [12, 13, 25]. Other countries in the top ten list that are involved in pharmaceutical remedies in HL are; Germany (MERCK), Japan (Takeda Pharmaceuticals), India (Avancecure Life Sciences), and China (Zhejiang Husun Pharma). More so, institutions in the United States were the leading institutions in HL-related research, constituting 60% of the top 20 institutions involved in HL research. The remaining institutions reside in Europe, North America; Germany (10%), Canada (10%), France (10%), Italy (15%), and Sweden (5%). The University of Texas MD Anderson Cancer Center, USA was observed to be the most productive institution for HL-related research. The University of Texas MD Anderson Cancer Center is devoted to cancer patient care, research, education, and prevention [26]. On the other hand, UniKlinik Koln (University Hospital of Cologne) Germany is the largest hospital in Cologne and is among the leading research centres on cancer in Germany [27].

The comparative evaluation of the productivity of HL-related research and current health expenditure revealed that the higher the current expenditure, the higher the productivity in HL-related research, with some exceptions: United Kingdom, France, Canada, Japan, Spain and Netherlands that their current health expenditure far exceeds their participation index. In summation the United States had the highest CHE (19% of GDP), followed by Germany (13% of GDP).

Evaluation of the correlation between productivity in HL-related research and Gross Domestic Product on research and development (R&D). Japan had the highest GDP dedicated to R&D among the top 10 most productive countries. Only three countries (Japan, United States and Germany) had GDP dedicated to R&D above the OECD (Organization of Economic Cooperation and Development) recommended average of 2.3%. On the other hand, six countries (Japan, The United States, Germany, China, France and Netherland) had GDP on R&D above the EU recommended average of 1.9%. The scientific productivity of a country is often a reflection of its earlier investment in research and development [13, 25].

Engert A, Diehl V, Younes A, Borchmann P, Ansell SM, Connors JM, Zinzani PL, Hansmann ML, Cozen W and Brice P. were the top ten most productive authors in the HL-related research. While Engert A focused mainly on treatment of HL, Diehl V and Younes A focused on treatment and molecular characterization of HL. On the other hand, Borchmann P, Ansell SM focused on treatment and diagnosis of HL. Zinzani PL focused on treatment and prognostic factors of HL, while Hansmann ML pitched with diagnosis and molecular characterization of HL. Cozen W carved his niche in risk factors and molecular characterization of HL. Connors JM delved into all of treatment, epidemiology, prognostic factors and molecular characterization of HL. Lastly, Brice P focused on Treatment, prognosis and diagnosis of HL.

The major journals utilized in the dissemination of HL-related research were Leukemia and Lymphoma, Journal of Clinical Oncology, British Journal of Haematology. Blood, Annals of Oncology, Annals of Haematology, Haematological Cancer, Bone Marrow, Transplantation and Pediatric Blood and Cancer. The centrality of these journals makes them focal point to be looked for, in future breakthrough in HL-research. The most productive journal in HL-related research belonged to the Q3 category, while the remainder were mostly Q1. This presents an interesting dynamic in academic publishing, as most biomedical scientists expect most productive journals in every discipline to fall in Q1. The top position of the Q3 journal suggests that it serves a critical niche within HL-research. As the name implied, the journal focused specifically on Leukemia and Lymphoma, hence, attracting high volume of specialized studies that other broader or more general Q1 journals might not prioritize. The overall mixed ranking of the top productive journals in HL-research highlights a balance between prestige and practicability. The dominance of a Q3 journal observed here, underscores the importance of niche specialization, while the prevalence of Q1 journals reflects the high value placed on quality, visibility, and academic impact. This dynamic illustrates how researchers navigate the complex landscape of academic publishing to disseminate their research findings effectively.

The article “Recommendation for initial evaluation, staging and response assessment of Hodgkin and non-Hodgkin lymphoma: The Lugano classification” was the most cited article (n = 3,023) with an average citation of 377.9/year. The article was a conference recommendation for initial evaluation, staging and response evaluation of HL and NHL. It was published open access in the Journal of Clinical Oncology (A toll access journal with 12 months embargo period) by Cheson BD et al. 2014. The second most cited article; “PD-1 blockade with nivolumab in relapsed or refractory Hodgkin lymphoma” is an original article reporting on the use of nivolumab in relapsed or refractory HL published open access in the New England Journal of Medicine (a delayed open access journal) by Ansell SM et al., 2015. Though the second most cited (n = 2732), this article had the highest average citations per year (390.3/year). The next is the clinical trial tagged “Results of pivotal phase II study of brentuximab vedotin for patients with relapse or refractory Hodgkin´s lymphoma” published open access in the Journal of Clinical Oncology by Younes et al., 2012 with a total citation of 1,204. Overall, six of the top 10 articles were original articles, two (2) were randomized clinical trials, one was a special article (recommendation). More so, seven (7) were published toll access while the remaining 3 were published open access. This trend once again crops up the argument of the “advantage of open access publication over toll access with respect to citation impact”. The Journal of Clinical Oncology published three (3) of the top 10 most cited articles. Only three (3) of the journals (Journal of Clinical Oncology, Lancet Oncology and Blood were dedicated to hematology and hematological malignancies. The rest were broad discipline journals. All the top most cited articles were published in journals with impact factors more than 4.

This study is prone to potential limitations that are inherent with bibliometric studies. First, the criteria set by the databases used determines the output of the downloaded datasets. Secondly, we may have excluded articles on Hodgkin lymphoma if the authors did not put our inclusion criteria descriptors in their title or keyword. More so, national/local journals not indexed in Scopus, Web of Science and PubMed will also be automatically excluded.

Conclusion

Scientific production in Hodgkin lymphoma was found to be saturated with high transience index. This study provides a reference for oncologists, epidemiologist, funders, policy decision makers, academics and Hodgkin lymphoma researchers.

Abbreviations

CHE

Current Health Expenditure

GDP

Gross Domestic Product

HL

Hodgkin lymphoma

HRS

Hodgkin and Reed-stern

JCR

Journal Citation Report

LP

Lymphocyte predominant

NHL

Non – Hodgkin lymphoma

NLPHL

Nodular lymphocyte-predominant Hodgkin lymphoma

OECD

Organization of Economic Cooperation and Development

PRISMA

Preferred reporting items for systematic reviews and meta-analysis

R&D

Research and Development

SPSS

Statistical Package for the Social Sciences

Author contributions

Conceptualization: HUO; Study design: FJP, HUO, ENO. Data curation and analysis: FJP, HUO. Data interpretation: HUO, FJP, KNI, EEA, AO, JEE, ENO, UOE, MRA, COO, EAU, KJE, NPN. Data validation: FJP, SOU, KNI, MOI, KJE, IKU, AO, NPN, ENO, EOB, OCD, CPE, DAA, EAA, IMO, PM, VOO, UCA, CJVO, UTE, EFN, SIO, HIU, ASO, IOO, JIO, JIU, EO, OOA, FLM. Figure and software analysis: FJP, HUO, ENO. Initial manuscript draft: HUO, MRA. All authors read, edited and approved the final manuscript.

Funding

There was no specific funding for this research.

Data availability

Datasets generated and analyzed in this study are within the article. The primary source of data, Scopus, Web of Science and Pubmed are publicly available.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.