Tivozanib in renal cell carcinoma: a systematic review of the evidence and its dissemination in the scientific literature.

backgroundTivozanib (Fotivda) is an anti-angiogenic tyrosine kinase inhibitor that was denied access to the US market by the Food and Drug Administration (FDA). In contrast, it was granted approval by the European Medicines Agency (EMA) for the treatment of Renal Cell Carcinoma in adults. Given the conflicting decisions from these regulatory agencies, the objectives of the following study are (i) to critically review the evidence supporting the approval of tivozanib; (ii) to analyse the dissemination of this evidence in the literature by way of a citation analysis.

methodsPivotal trials were searched by two independent reviewers using Medline, Cochrane Library, ClinicalTrials.gov and the European Public Assessment Report. The risk of bias for each trial was then inductively assessed. Articles citing any of these trials were identified using Web of Sciences. Finally, the quality of the citations was evaluated by two independent reviewers according to standard data extraction methods.

resultsThe search for primary evidence identified two pivotal studies: TIVO-1 upon which the FDA and the EMA decisions were based, and TIVO-3 which was conducted after the agencies' decisions had been issued. The TIVO-1 trial presented several limitations that compromised causal inference, in relation to (i) design (absence of blinding, inappropriate comparator, and one-way crossover), (ii) poor internal consistency in the results for the primary endpoint, (iii) a discrepancy between a benefit observed for progression-free survival (HR: 0.80, 95% CI [0.64-0.99]) and the absence of difference for overall survival (HR: 1.25, 95% CI [0.95 - 1.62]). Our citation search protocol identified 229 articles that cited TIVO-1 in the 7 years following its publication, among which 151 (65.9%) citing articles discussing efficacy. Presence of spin was identified in 64 (42.4%) of these 151 citing articles, and 39 (25.8%) additional articles citing results without providing enough elements to interpret the TIVO-1 results.

conclusionEMA's approval was based on a single pivotal trial presenting critical limitations, rendering the results from the trial potentially inconclusive. The broad dissemination of TIVO-1 results in the scientific literature may have been affected by spin or results were presented in an inadequate critical manner.