Posted: Friday, June 3, 2022
Based on a cohort study of the Flatiron Health database, use of erdafitinib, the first gene-targeted therapy for urothelial carcinoma, was limited by drug toxicity, high drug cost, and inadequate fibroblast growth factor receptor (FGFR) testing. Despite study limitations, Ronac Mamtani, MD, MSCE, of the University of Pennsylvania, Philadelphia, and colleagues indicated blood-based testing identifies susceptible alterations at a similar rate to tissue testing. Additionally, blood-based testing may identify FGFR alterations when tissue-based testing does not. These findings were published in JAMA Oncology.
“The uptake of this drug was unexpectedly low, which suggests there are significant barriers to its use, including obstacles that prevent people from getting tested for the erdafitinib-susceptible gene mutation,” said study lead author Vivek Nimgaonkar, BA, BS, of the University of Pennsylvania, in an institutional press release.
The study analyzed the Flatiron Health database of bladder cancer cases between 2019 and 2021. Eligible patients had been diagnosed with advanced urothelial cancer, received first-line platinum-based chemotherapy, and started a line of therapy between May 2016 and September 2021.
Of the 761 patients included in the study, 343 (45.1%) had FGFR testing recorded. Of the 343 tested, 71 (20.7%) had a susceptible FGFR alteration. A total of 30 patients (42.3%) with susceptible FGFR alterations received erdafitinib. After erdafitinib approval, FGFR testing increased, although erdafitinib initiation remained low among patients with FGFR alterations.
Among patients who underwent FGFR testing, 305 (88.9%) had tissue-based testing, and 74 (21.6%) had blood-based testing, resulting in similar FGFR alteration detection rates. The detection rates of the tissue-based testing were 19.3% (59 of 305) and of the blood-based testing, 18.9% (14 of 74). Among 36 patients with both tissue- and blood-based testing, 6 susceptible alterations were detected, 2 by tissue-based testing and 6 by blood-based testing. The monthly uptake rates of erdafitinib were significantly lower than those of immunotherapy. The median overall survival of non-trial and trial patients was similar at 8.97 months.
Disclosure: For full disclosures of the study authors, visit jamanetwork.com.