Immune checkpoint inhibitors: A bibliometric analysis of research trends and hotspots based on the most frequently cited clinical trials (2013 - 2021).

Objective: To quantitatively and qualitatively evaluate research trends and hotspots for immune checkpoint inhibitors (ICIs), according to the most frequently cited clinical trials.

Background: Numerous clinical trials have been carried out using ICIs for activating anti-tumor immunity in cancer patients. The most frequently cited clinical trials have been used as a database for achieving the objectives of this analysis.

Materials and methods: The most frequently cited articles on ICIs meeting the inclusion criteria were extracted from the Web of Science database. Citation report information including annual outputs, most relevant journals, and country of origin together with burst references, keywords, information on co-occurrence, citation networks, and cluster topics were analyzed using standard bibliometric procedures.

Results: A total of 112 most frequently cited articles on clinical trials of ICIs were retrieved for the period 2013 to 2021 of which the journal JAMA Oncology had the highest number of citations. Most studies originated in the U.S., and therefore studies from this country had a determinant effect of the results of the investigation. Burst reference topics included studies on ipilimumab for melanoma, anti-PD-L1 antibody in advanced cancer, anti-PD-1 antibody in cancer, nivolumab combined with ipilimumab or as monotherapy in untreated melanoma, and pembrolizumab for PD-L1 positive non-small-cell lung cancer. Nine clusters were grouped in the citation network. The topic/keywords "cancer", "immunotherapy", "PD-1 blockade", "PD-L1", "expression", "ipilimumab", "nivolumab", "pembrolizumab", and "safety" were the search priorities, whereas "multicenter", "resistance", "adverse events", and "renal-cell carcinoma" were seen as emerging topics in this specific field.

Conclusion: The bibliometric analysis of the most frequently cited clinical trials with ICIs provided information on the characteristics of the studies evaluated as well as hotpots and trends in evolving immunopharmacotherapy research on ICIs.