Visual symptoms in a patient treated with MEK inhibitors

to report an uncommon presentation of Encorafenib-Binimetinib retinal side effects.

A 56-year-old Caucasian woman, naïve to previous chemotherapies, was started on Encorafenib/Binimetinib for metastatic melanoma. After seven hours from the first 45 mg Binimetinib dose, the patient developed blurry vision with coloured halos. The symptoms were transient and the following day a complete ophthalmological examination revealed the presence of subretinal fluid (SRF) at Optical coherence tomography (OCT). After one week, the patient remained asymptomatic, with no signs of SRF at the follow up reevaluation. However, six weeks later, the symptoms originally experienced with the first drug intake appeared again. This time fundus examination revealed an irregular macular region. At infrared OCT an almond shaped hyporeflective lesion, surrounded by hyperreflectivity, was demonstrated without signs of SRF. Encorafenib/Binimetinib was continued at the same dose and strict monitoring was scheduled, according to the European Medicine's Agency indication to withhold the drug only in presence of symptomatic retinal pigment epithelial detachment.

Visual symptoms associated with SRF induced by Binimetinib have been described in the literature. In our case, visual symptoms were experienced by the patient at different times, both with and without evidence of SRF. This finding seems to suggest that while Binimetinib-induced SRF is an asymptomatic finding in most cases, with excellent outcome and rapid resolution, visual symptoms could be initially triggered by detectable SRF, yet persist without any further evidence of abnormal fluid accumulation and manifest intermittently.