Dr. Iyer on Erdafitinib-Related Hyperphosphatemia in Metastatic Urothelial Cancer

Gopa Iyer, MD, medical oncologist, Memorial Sloan Kettering Cancer Center, discusses treatment-emergent hyperphosphatemia with erdafitinib (Balversa) in patients with metastatic urothelial cancer.

In April 2019, the FDA granted accelerated approval to erdafitinib for the treatment of patients with locally advanced or metastatic urothelial cancer with an FGFR3 or FGFR2 alteration that has progressed on platinum-containing chemotherapy.

FGFR inhibitors like erdafitinib appear to increase phosphorus reabsorption in the body and lead to hyperphosphatemia, explains Iyer.

Generally, hyperphosphatemia can be controlled with dietary changes such as reducing dairy and meat intake and adding oral phosphate binders like sevelamer (Renagel), says Iyer.

Notably, phosphate levels indicate response to erdafitinib, says Iyer. The FDA designation recommends starting patients on erdafitinib at a daily dose of 8 mg. If a patient’s phosphate level is <5.5 mg/dL after 2 to 3 weeks of treatment, the dose should be increased to 9 mg once daily to increase FGFR inhibition.