# Early Optical Coherence Tomography Signs of Erdafitinib-Induced Retinopathy

## TL;DR

This case study shows early signs of retinal toxicity from erdafitinib, a cancer drug, detected through optical coherence tomography (OCT) before noticeable vision changes.

## Contribution

The study identifies specific OCT changes as early indicators of erdafitinib-induced retinopathy.

## Key findings

- OCT showed ellipsoid zone thickening and interdigitation zone prominence after one month of erdafitinib treatment.
- Subretinal fluid was observed but resolved after discontinuing the drug.
- OCT returned to baseline two months after stopping erdafitinib.

## Abstract

A 64-year-old male presented for a baseline ophthalmic exam before beginning erdafitinib, a fibroblast growth factor receptor (FGFR) inhibitor, for stage 4 papillary urothelial cancer. Baseline optical coherence tomography (OCT) and ophthalmic examination were unremarkable. After one month of treatment, his OCT demonstrated a significant thickening of the ellipsoid zone and prominence of the interdigitation zones along with a small amount of subretinal fluid. Two months after discontinuation of the medication, the OCT returned to baseline.

Erdafitinib is a Food and Drug Administration (FDA)-approved treatment for unresectable or metastatic urothelial cancer with FGFR2 or FGFR3 mutations. However, retinal toxicity can ensue with the initiation of the drug and cause subjective vision changes and OCT abnormalities. The drug may exert toxic effects on retinal pigment epithelium, which may be seen through interval OCTs and visualization of the interdigitation zone. Therefore, pronunciation of the ellipsoid and interdigitation zone on OCT may allow for surveillance of early manifestations of erdafitinib-induced retinal toxicity.