Management of Fibroblast Growth Factor Inhibitor Treatment-emergent Adverse Events of Interest in Patients with Locally Advanced or Metastatic Urothelial Carcinoma.

Background: Erdafitinib is indicated for the treatment of adults with locally advanced/metastatic urothelial carcinoma and susceptible Objective: To better understand the frequency and management of select treatment-emergent adverse events (TEAEs) to enable optimal fibroblast growth factor receptor inhibitor (FGFRi) treatment. Design setting and participants: Longer-term efficacy and safety results of the BLC2001 (NCT02365597) trial in patients with locally advanced and unresectable or metastatic urothelial carcinoma were studied. Intervention: Erdafitinib schedule of 8 mg/d continuous in 28-d cycles, with uptitration to 9 mg/d if serum phosphate level was <5.5 mg/dl and no significant TEAEs occurred. Outcome measurements and statistical analysis: Adverse events were graded using National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. The Kaplan-Meier methodology was used for the cumulative incidence of the first onset of TEAEs by grade. Time to resolution of TEAEs was summarized descriptively. Results and limitations: At data cutoff, the median treatment duration was 5.4 mo among 101 patients receiving erdafitinib. Select TEAEs (total; grade 3) were hyperphosphatemia (78%; 2.0%), stomatitis (59%; 14%), nail events (59%; 15%), non-central serous retinopathy (non-CSR) eye disorders (56%; 5.0%), skin events (55%; 7.9%), diarrhea (55%; 4.0%), and CSR (27%; 4.0%). Select TEAEs were mostly of grade 1 or 2, and were managed effectively with dose modifications, including dose reductions or interruptions, and/or supportive concomitant therapies, resulting in few events leading to treatment discontinuation. Further work is needed to determine whether management is generalizable to the nonprotocol/general population. Conclusions: Identification of select TEAEs and appropriate management with dose modification and/or concomitant therapies resulted in improvement or resolution of most TEAEs in patients, allowing for continuation of FGFRi treatment to ensure maximum benefit. Patient summary: Early identification and proactive management are warranted to mitigate or possibly prevent erdafitinib side effects to allow for maximum drug benefit in patients with locally advanced or metastatic bladder cancer.