ctDNA- and cfDNA-based liquid biopsy in bladder cancer and urothelial carcinoma: bibliometric mapping and cross-database coverage analysis, 2008-2025.

BACKGROUND

Circulating tumour DNA (ctDNA), cell-free DNA (cfDNA) and urinary tumour DNA are increasingly studied in bladder cancer and urothelial carcinoma. We mapped the development, knowledge structure and clinical emphasis of this ctDNA/cfDNA-centred literature and assessed its coverage across three bibliographic databases.

METHODS

Web of Science Core Collection (WoSCC), Scopus and PubMed/MEDLINE were searched on July 31, 2026, for records published in 2008-2025. Reviewer-expanded strategies included liquid biopsy, ctDNA/cfDNA, molecular residual disease, molecular relapse, tumour-informed assays, urinary DNA, methylation, TERT and FGFR3. WoSCC was the primary mapping database; Scopus and PubMed/MEDLINE were coverage comparators. Python, VOSviewer and CiteSpace were used for descriptive and network analyses. Newly retrieved WoSCC records underwent duplicate independent screening and full third-reviewer quality control.

RESULTS

The searches retrieved 1,903 WoSCC, 3,201 Scopus and 230 PubMed/MEDLINE records. After WoSCC deduplication and eligibility assessment, 494 records formed the main set and 698 formed a contextual set. The main set received 17,031 citations (median 19; interquartile range 7-42), and annual output reached 82 records in 2025. Scopus covered 456/494 main records and PubMed/MEDLINE covered 93/494. Among 557 newly assessed records, the reviewers initially agreed on 433 (77.7%; Cohen's kappa, 0.620); all records then underwent third-reviewer full-text quality control.

CONCLUSIONS

The expanded search identifies a larger DNA-focused literature than the original strategy and confirms unequal database coverage. Thematic clusters and citation bursts trace a shift from early methylation-marker research towards ctDNA-based molecular residual disease assessment and perioperative treatment stratification. Bibliometric prominence describes research activity, not diagnostic accuracy, predictive validity or treatment benefit.