Cancer treatment

A method for the treatment of urothelial cancer harboring at least one FGFR genomic alteration, which method comprises:

• a) administering to a subject in need thereof, 8 mg of erdafitinib daily on a continuous basis;
• b) measuring the serum phosphate levels of the subject on a treatment day during the first cycle of erdafitinib treatment;
• and
• c-1) when the serum phosphate levels are <5.5 mg/dL, erdafitinib is administered in an amount of 9 mg daily, on a continuous basis;
• or
• c-2) when the serum phosphate levels range from and including 5.5 mg/dL to <7 mg/dL, erdafitinib is further administered in an amount of 8 mg daily, on a continuous basis;
• or
• c-3) when the serum phosphate levels are ≥7 mg/dL, the erdafitinib treatment is interrupted temporarily.