Noninvasive direct detection of ocular mucositis by in vivo confocal microscopy in patients treated with S-1

PURPOSE S-1 is an oral antineoplastic agent that contains a prodrug of 5-fluorouracil and has adverse effects on skin, alimentary tract mucosa, and the ocular surface. We investigated the effects of S-1 on the corneal epithelium by in vivo confocal microscopy and histopathologic analysis. METHODS Twelve patients with eye problems related to S-1 treatment participated in the study. Twenty eyes of ten subjects were evaluated by laser-scanning confocal microscopy. Corneal epithelial debridement as a diagnostic therapy and histopathologic analysis were performed for five eyes of three subjects affected in the pupillary zone of the cornea. RESULTS Slitlamp examination revealed a local limbal abnormality characterized by epithelial invasion toward the center of the cornea in all 24 eyes. In vivo confocal microscopy revealed an altered structure of the corneal epithelium with abnormal epithelial cells and inflammation. One of five specimens subjected to cytologic diagnosis showed moderate dysplasia. Hematoxylin and eosin staining showed that each abnormal epithelial sheet lacked the stratified structure of the normal corneal epithelium. Immunofluorescence analysis revealed the presence of cells positive for one, both, or neither of cytokeratins 12 and 4 in each lesion. CONCLUSIONS S-1 can induce ocular mucositis with dysplasia, likely affecting cellular functions, including differentiation, of the corneal epithelium. In vivo confocal microscopy allowed the noninvasive detection of cellular changes in the cornea as an adverse effect of S-1 administration.