Rapid radiological response of leptomeningeal carcinosis and prolonged survival to encorafenib and binimetinib in BRAF-mutated melanoma

Among solid tumors, malignant melanoma (MM) has the highest risk of metastasis to the leptomeninges, for which a specific therapeutic regimen has not been established yet. This case report describes a rapid partial response to leptomeningeal disease (LMD) in a patient with a BRAF V600K-mutated MM. A 69-year-old man affected by metastatic melanoma was initially treated with benefit with targeted therapy with encorafenib and binimetinib, which was discontinued several times because of toxicity or intolerance, and then with dabrafenib and trametinib, which were also poorly tolerated. During the treatment pause, the patient, who had refused to receive immunotherapy developed LMD and was started again on targeted therapy with reduced dosage of encorafenib and binimetinib. A few days after starting this treatment, MRI showed an important reduction of the perilesional edema and then, after a few months, a disease response. The patient had a long survival of approximately 14 months from this diagnosis. To the best of our knowledge, this is the first report describing rapid radiological response, clinical benefit, and prolonged survival with encorafenib and binimetinib in patients affected by LMD from melanoma.