Introduction

Renal ablation has emerged as a minimally invasive treatment option for kidney cancer, especially for patients with small renal tumors [1, 2]. This technique involves the destruction of cancerous tissue in the kidney using extreme temperatures or other forms of energy, such as radiofrequency or laser ablation. The use of ablation techniques for renal tumors dates back to the late 1990s, when percutaneous radiofrequency ablation (RFA) was first used as a treatment [3]. Since then, several other ablative techniques, such as cryoablation [4] and microwave ablation [5], have been developed and refined.

The two primary types of energy used in renal ablation are heat and cold. Radiofrequency ablation (RFA) uses high-frequency radio waves to generate heat and destroy cancerous tissue. During the RFA procedure, a small needle is inserted through the skin and into the tumor, and an electrode is then passed through the needle and positioned within the tumor. The electrode generates heat, which destroys the tumor cells. Cryoablation, on the other hand, uses extreme cold to freeze and destroy cancerous tissue. It involves the insertion of one or more small probes through the skin and into the tumor. These probes are then cooled to very low temperatures, which freezes the cancerous tissue and destroys the tumor cells.

Several studies have shown that RFA and cryoablation have outcomes similar to surgery in terms of tumor control and overall survival rates for patients with small renal tumors [4, 5]. Renal ablation procedures have also been associated with lower rates of complications, reduced hospital stays, and faster recovery times compared to surgery. However, it is crucial to note that renal ablation may not be suitable for all patients, particularly those with larger tumors or tumors located in certain areas of the kidney. Furthermore, long-term outcomes of renal ablation procedures are still being studied, and it is unclear how effective these procedures will be in preventing cancer recurrence over the long term [6]. Thus, it is necessary to evaluate each patient’s individual case and weigh the risks and benefits of renal ablation versus surgery.

Despite the wealth of publications investigating renal cancer ablation in the past decade, a systematic analysis of the data found in these publications has yet to be conducted. Bibliometrics has been demonstrated as an effective tool for examining the most influential authors, papers, countries or regions, establishing collaboration networks, and identifying research trends in specific fields [7]. Therefore, our study utilizes a bibliometric approach to synthesize and consolidate the knowledge base on renal cancer ablation.

The primary objective of our study is to identify the most influential publications, authors, institutions, and countries in the field of renal cancer ablation. In addition, we aim to elucidate the major research themes and emerging topics in this field. Through our analysis, we seek to offer a comprehensive overview of the knowledge base surrounding renal cancer ablation, thus facilitating a better understanding of its progression and development among researchers [8].

Methods

To ensure a comprehensive examination, we gathered articles from the Web of Science [9] database, which is renowned for its vast journal coverage. Two authors conducted independent searches using various search terms to minimize bias, and any discrepancies were resolved by a third author.

The data were collected on April 18, 2023, using the search terms “ablation RCC” OR “ablation renal carcinoma” OR “ablation renal cancer,” and we filtered the results to include only “articles.” The search yielded 285 documents. No additional restrictions were applied.

We collected various types of information during bibliometric data collection, including authors, publication year, journal, citations, affiliations, author keywords, and references. We used authors’ affiliations to obtain data on institutions and countries, which we analyzed using VoxViewer [10, 11] and Microsoft Excel [12]. We obtained journal impact factors and rank/quartile from the 2021 Clarivate “Journal Citation Reports” database [13] and the 2021 SCImago Journal Rank [14], respectively.

We used several software tools, including Microsoft Excel [12], Tableau [15], VoxViewer [10, 11], and R [16], for data refinement and statistical analysis. For statistical analysis, we used the Bibliometrix [17] package with the assistance of Biblioshiny. We uploaded the Web of Science [9] dataset to Biblioshiny [5] via R [16] for analysis, while Tableau [15], VoxViewer [10, 11], and Web of Science [9] analysis tools were used for result visualization. p values < 0.05 were considered significant.

Results

A total of 285 documents were detected by the search. Figure 1 represents the years of publication along with number of articles published that year. As observed in the graph, we calculated a statistically significant positive correlation between the year of publication and number of articles (r2 = 0.643, p < 0001). By trend prediction, there will be 17 articles published in 2023 (number of articles published = 0.547539*publication year ± 1090.28).

Fig. 1
figure 1

Graph of number of articles published by year

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The paper that has received the highest number of citations to date is “Radiofrequency ablation of renal cell carcinoma: Part I, indications, results, and role in patient management over a 6-year period and ablation of 100 tumors” [2], which was published in the “American Journal of Roentgenology” (AJR) and has garnered 427 citations. Following this, the next most cited papers are Refs. [1] and [3]. The paper with the highest average yearly citation count of 22 is also Ref. [2], followed by Ref. [1]. For a list of the top 20 most cited papers, please refer to Table 1 (Supplemental Table 1 provides the full table).

Table 1 Top 20 most cited articles on renal cancer ablation (descending order by citations)
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A total of 103 different academic journals have published research on ablation procedures for the treatment of renal cancers. Among these, the top 10 most prolific journals contributed 48% of all articles on this topic (138 out of 285). The most prolific journal was found to be the “Journal of Vascular and Interventional Radiology” (JVIR) with 23 publications, followed closely by “Cardiovascular and Interventional Radiology” with 22 publications and “Journal of Urology” with 17 publications. The journal with the highest number of citations was “Radiology” with 1114 citations, followed by the “American Journal of Roentgenology” with 1075 citations. In terms of the highest average citations per paper published, “European Radiology” stood out with an average of 188 citations per paper.

Out of the 103 academic journals surveyed, those focused on Radiology published the most articles (141) and received the highest number of overall citations (4078), accounting for 35 of the journals analyzed. Urology journals came in second place with 78 articles and 2,525 citations, while Oncology journals were in third place with 36 articles and 312 citations (Fig. 2). The majority of journals (66%) were of a hybrid publishing model while 23% were completely open access.

Fig. 2
figure 2

a Left: subject of journal vs. number of articles published. b Right: subject of Journal vs. total citations

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The Impact Factors (IF) [13] of the top ten most prolific journals varied from 2.619 to 29.156. The journal with the highest IF overall was “Annals of Internal Medicine” with an IF of 51.598. Journal Metrics for the top 19 journals ranked by the IF can be found in Table 2. Approximately 49% of the journals had a good IF (> 3), and these journals published 58% (165 out of 285) of all articles on the topic.

Table 2 Top 19 highest impact factor Journals (descending order by impact factor)
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Our analysis reveals a statistically significant positive correlation between IF and both Total Citations (r2 = 0.11, p = 0.0012) and Average Citations per Paper (r2 = 0.312, p < 0.0001). However, we found no significant correlation between IF and the number of articles published (r2 = 0.008, p = 0.393). It should be noted that we considered results to be significant if p < 0.05. A graphical representation of these correlations can be seen in Fig. 3.

Fig. 3
figure 3

Correlation graphs of impact factor (IF) vs. citation metrics. a Top: IF vs. number of articles published. b Middle: IF vs. total citations. c Bottom: IF vs. average citations per paper

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A total of 33 countries and 242 institutions were involved in the publication of the 285 articles on renal cancer ablation. Harvard was the most productive institution in terms of both article number and Total Citations, as demonstrated by Fig. 4a and b, respectively. Remarkably, Harvard’s output of 33 publications garnered a total of 2231 citations, significantly exceeding that of the second most productive institution, which produced 17 articles, and the second most cited institution, which received 512 citations. Among the top 20 most productive institutions, 9 were situated in the US, followed by 3 in China.

Fig. 4
figure 4

a Top: top 20 institutions ranked by total number of articles, with citation counts written beside bar. b Bottom: top 20 institutions ranked by total number of citations with article count written beside bar

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The most collaborative institution was University of Milan with 36 links and 49 link strength. The second most collaborative was Cornell which also had 36 links with 42 link strength. There was a weak positive correlation between number of links and articles (r2 = 0.75, p = 0.02) or also citations (r2 = 0.03, p = 0.032).

The United States emerged as the most prolific and highly cited contributor, having produced 113 documents and garnered a total of 4101 citations. In second place, China yielded 52 documents and 782 citations. Notably, Italy exhibited the highest degree of collaboration, with 14 links, followed closely by Germany and the United States, each with 13 links. Of note, the US demonstrated the greatest link strength, at 38. Six principal collaborative clusters were identified among countries, as outlined in Table 3. The rest of the countries had no collaboration clusters. It is worth highlighting that the US and China frequently collaborated and exhibited the highest aggregate output in terms of articles and citations.

Table 3 Country collaboration clusters
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In the literature on renal cancer ablation, 1355 distinct authors have contributed to research in this area. The top seven most prolific authors are displayed in Fig. 5a, with Liang, P. (18) [18] and Yu, J. (17) [19] holding the top two positions in terms of the number of articles authored. On the other hand, Fig. 5b showcases the top seven most cited authors, with Mueller, P.R. (1493 citations) [1, 2] and Gervais, D.A. (1361 citations)[1, 2] occupying the top two positions. Both of these pairs of authors were very frequent collaborators.

Fig. 5
figure 5

a Top: top 10 most prolific authors with number of total citations beside bar. b Bottom: top 10 most cited authors with number of publications beside bar

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Notably, the analysis revealed a trend in the publishing behavior of authors affiliated with different institutions. Chinese-affiliated authors tended to publish a greater number of articles individually, while authors from American institutions tended to have a higher number of individual citations.

Gervais, D.A. was the most highly connected author in this field, with 32 links and a total link strength of 36. To further understand the collaboration patterns, the top authors were divided into collaboration clusters and their associated links and link strength are presented in Supplemental Table 2. These findings provide insight into the collaborative nature of the field and highlight key authors and clusters of collaboration.

The three most frequently used author keywords were “renal cell carcinoma,” “radiofrequency ablation,” and “microwave ablation,” indicating the prevalence of these topics in the literature. The top ten author keywords are presented in Table 4, providing an overview of the most commonly studied and discussed topics in the literature.

Table 4 Top 20 author
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Interestingly, some recurring author keywords included “sorafenib” [20] and “transarterial embolization” [21] suggesting that multiple treatments are being used in conjunction with ablation to improve overall outcomes. “Von-Hippel Lindau syndrome” [22, 23] was also a commonly referenced keyword, which is a disease associated with a high risk of renal cancer. These findings provide insight into the broader context in which renal ablation is studied and practiced.

The author keyword analysis depicted in Fig. 6 demonstrates an increase in the mentions of cryoablation and microwave ablation since 2020, surpassing the mentions of radiofrequency ablation (RFA). This trend suggests a growing interest and focus on these alternative ablation techniques in the field of percutaneous renal ablation.

Fig. 6
figure 6

Author keyword frequency over time

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Overall among these studies, radiofrequency ablation (RFA) was the most frequently studied technique, with 145 (50%) of the studies focusing solely on RFA. Microwave ablation was the focus of 54 (18%) of the studies, while thermal ablations, which encompassed both RFA and microwave ablation, were the subject of 25 (9%) of the studies. The remaining studies were distributed among several less commonly studied ablation techniques, including photo-thermal/laser ablations (6 studies, 1996–2020), cryoablations (3 studies, 2018–2023), high-intensity focused ultrasound (HIFU) (3 studies, 2010–2016), ethanol ablation (3 studies, 1986–2010), irreversible electroporation (IRE) (2 studies, 2012–2015), and boiling histotripsy (BH)(1 study, 2019).

Only a small number directly compared different ablation techniques. Specifically, seven studies compared RFA to cryoablation (2003–2023), one study compared RFA to microwave ablation (2018), and one study compared all three ablation techniques (RFA, microwave, and cryoablation; 2019). The remaining studies did not specify which ablation technique was being studied in their titles.

Discussion

An analysis of 285 papers on renal cancer ablation was conducted using the Web of Science [9] database. These papers were published in 103 academic journals and involved 1355 authors and 242 institutions from 33 countries. One of the significant observations in the text is the statistically significant positive correlation between the year of publication and the number of articles on renal cancer ablation. This growth in research output suggests a rising interest and focus on renal cancer ablation as a viable treatment option. Further research is required to determine whether this is due to advances in technology, increased prevalence of renal cancer [24, 25], or improved access to resources and funding.

Radiology Journals are highly cited due to their focus on medical imaging and related fields, which makes them a natural choice for publishing research on percutaneous renal ablation. While Interventional Radiologists are the primary physicians performing these procedures, it is important to note that other medical specialties such as Urology and Oncology are also contributing significantly to the field. Collaboration among these specialties can lead to a more comprehensive understanding of percutaneous renal ablation, ultimately improving patient care.

Our analysis found a positive correlation between Impact Factor (IF) and both Total Citations and Average Citations per Paper in the field of percutaneous renal ablation. This suggests that publishing in high-IF journals can lead to greater exposure and impact for research in this field. However, we found no significant correlation between IF and the number of articles published, indicating that the number of articles published in a given journal is not necessarily a reflection of its impact or influence in the field [26]. These findings highlight the importance of carefully choosing the appropriate journal for publication to ensure maximum impact and influence of research in percutaneous renal ablation.

We found that the US was the most prolific and highly cited country in this field, followed closely by China. This suggests that the US and China are major players in the global research landscape of percutaneous renal ablation, with a significant influence on shaping the field. The research output and impact of these two countries in percutaneous renal ablation can be attributed to a variety of factors, including collaboration (as they are frequent collaborators with each other), access to resources, funding, and a strong research culture.

It is worth noting that the concentration of research output in a few select countries does not imply a lack of interest or progress in the field elsewhere. Rather, it highlights the need for greater collaboration and sharing of knowledge across borders to further advance the field of percutaneous renal ablation. Such collaboration can lead to a more comprehensive understanding of the disease, which can ultimately translate to better diagnosis, treatment, and management of patients with renal cancer.

The outcomes of the author keyword analysis and the distribution of research on renal ablation modalities offer significant insights into the contemporary state of investigation and application in the domain of percutaneous renal ablation. Although radiofrequency ablation (RFA) is the most extensively examined method, the escalating keyword references to cryoablation [27, 28] and microwave ablation [29, 30] since 2020 signify an expanding interest and concentration on alternative ablation approaches within the realm of percutaneous renal ablation.

At present, the predominant renal ablation technique is RFA [1, 2], classified as a thermal ablation due to its utilization of heat. Additional thermal ablations encompass microwave [29], photo-thermal/laser [31], and high-intensity focused ultrasound (HIFU) [32]. RFA is a minimally invasive modality employing high-frequency electrical currents to heat and eradicate cancerous tissue, frequently used for treating small tumors, and is typically safe and effective. Conversely, microwave ablation [29] utilizes high-frequency electromagnetic waves to heat and eliminate cancerous tissue, penetrating deeper into tissue compared to RFA, potentially offering increased efficacy in treating larger tumors. Photothermal/laser ablation [31] employs laser energy to heat and eliminate cancerous tissue, potentially proving especially effective for small tumors and those difficult to access with other methods. HIFU [32] uses focused ultrasound waves to heat and destroy cancerous tissue, also demonstrating efficacy in treating small, localized tumors.

Non-thermal ablation techniques encompass cryoablation [27, 30], irreversible electroporation (IRE) [33, 34], and ethanol ablation [34]. Cryoablation is a modality involving the freezing of cancerous tissue using a probe inserted into the tumor, with the extreme cold annihilating the tissue and the body ultimately reabsorbing the dead cells. Cryoablation may prove particularly effective for tumors situated near delicate structures, such as the ureter, as it can minimize the risk of damage to those structures. IRE employs brief, intense electrical pulses to generate minute perforations in cancerous cells, culminating in their destruction. IRE is a relatively novel technique, presently under investigation; however, preliminary results indicate that it may also be especially effective in treating tumors located near critical structures like the ureter. Ethanol ablation, an older and less frequently utilized technique, involves the injection of pure alcohol (ethanol) into a tumor to destroy it and is generally reserved for tumors that are untreatable with alternative methods.

In conclusion, our bibliometric analysis provides a comprehensive overview of the research landscape of renal cancer ablation. This information can aid future investigators in identifying research gaps, emerging trends, and potential collaborations, ultimately contributing to the advancement of renal cancer ablation techniques and improving patient outcomes.

Limitations

This study has several limitations to consider. Our study primarily focuses on analyzing the literature production surrounding renal cancer ablation, without delving into the clinical impact of the papers reviewed. Thus, it is important to note that our findings offer insights primarily into research trends and publication patterns rather than clinical outcomes. Selection bias may have occurred despite efforts to minimize it through separate searches by two authors; the search terms used may not have captured all relevant articles on renal cancer ablation, and restricting the search to the Web of Science [9] database may have excluded pertinent articles in other databases. Language bias may have been introduced due to Web of Science’s [9] focus on English-language publications, especially considering the significant impact of Chinese researchers in the field. Lastly, while the study assesses the primary focus of each article, a more detailed analysis of their content, methodologies, and conclusions could offer valuable insights into research trends, innovations, and controversies surrounding renal cancer ablation. These limitations should be acknowledged when interpreting the findings and drawing conclusions.