Early Detection of Serous Retinal Detachment During BRAF and MEK Inhibitor Therapy Through Community Pharmacist Telephone Follow-up and Hospital–Community Pharmacy Collaboration: A Case Report

Combination therapy with encorafenib, binimetinib, and cetuximab for BRAF V600E-mutated colorectal cancer is associated with early adverse ocular events, including serous retinal detachment. Therefore, careful monitoring of patients during outpatient treatment is essential. A 56-year-old woman with stage IV BRAF V600E-mutated colorectal cancer was treated with encorafenib, binimetinib, and cetuximab. Given the risk of adverse ocular events, hospital pharmacists requested that a community pharmacy provide intensive monitoring. On day 5, during a telephone follow-up by a community pharmacist, the patient reported visual symptoms but did not recognize their clinical significance. Suspecting a serious adverse ocular event, the community pharmacist advised immediate medical evaluation and submitted a tracing report to a hospital pharmacist. Both encorafenib and binimetinib were discontinued immediately, and ophthalmological examination confirmed a grade 2 serous retinal detachment. After the event was resolved, encorafenib and binimetinib were resumed at reduced doses on day 71. Continued follow-up after dose reduction enabled the detection of recurrent visual symptoms. The community pharmacist contacted the hospital pharmacist and submitted a tracing report. Because serous retinal detachment was confirmed as grade 1, the therapy was continued at reduced doses without interruption. Therapy continued until disease progression was observed on day 260. This case highlights the role of community pharmacists in monitoring adverse events during outpatient oral anticancer therapy. Scheduled telephone follow-ups, combined with hospital–community pharmacy collaboration, may facilitate the detection of adverse events, prevent progression to severe outcomes, and support continued treatment.