Bilateral Corneal Subepithelial Fibrosis Secondary To Erdafitinib: Two Cases Report.

To report two cases of bilateral corneal subepithelial fibrosis associated with erdafitinib, a fibroblast growth factor receptor (FGFR) inhibitor for bladder cancer.

Tertiary referral University Hospital Fundación Jiménez Díaz, Madrid (Spain).

Erdafitinib is a fibroblast growth factor receptor (FGFR) protein-tyrosine kinase inhibitor, which is used for locally advanced or metastatic bladder cancer with susceptible FGFR3 or FGFR2 genetic alterations.  Two patients who were on treatment with erdafitinib were referred to our clinic for visual acuity loss. First patient was diagnosed of bladder cancer and second patient was in a clinical trial for a high-grade intramedullary glioma. Complete ophthalmological examination was performed in every visit which included best corrected visual acuity (BCVA), slit-lamp examination, anterior segment optical coherence tomography (AS-OCT) and iconography. 

First patient was 83-year-old and pre-treatment BCVA was 0.9 in the right eye (RE) and 1.0 in the left eye (LE). After 7 months with Erdafitinib, BCVA decreased to 0.4 in RE and counting finder in LE. Second patient was 38-year-old, and his BCVA before starting erdafitinib was 1.0 in both eyes (OU). After 3 months with erfafitinib, his BCVA decreased to 0.7 OU. In both cases, slit-lamp examination revealed bilateral linear corneal epithelial fibrosis and severe punctate keratitis. AS-OCT showed hyperreflective subepithelium with nodular thickening. Topical fluorometholone and lubrication were started in both patients. However, corneal lesions persisted so erdafitinib was stopped. In 1 month, corneal lesions were resolved and BCVA improved.

Erdafitinib, a novel FGFR inhibitor, has been related to a variety of ocular toxicities including conjunctivitis, dry eye syndrome, severe punctate keratitis, corneal ulcers, stomal thinning, white cataracts and central serous retinal pigment epithelial detachment. Corneal subepithelial fibrosis has never been described before as an adverse event of erdafitinib, but should be taken into account as reported in these two cases. Fortunately, this adverse event appears to be reversible after discontinuation of the medication.

Therefore, regular ocular examinations should be performed in patients who are going to start treatment with erdafitinib to detect early ocular side effects and to stop medication, if necessary.