Durable complete remission of leptomeningeal melanoma by intrathecal methotrexate maintained with systemic ipilimumab.

Leptomeningeal disease (LMD) is a complication of metastasized melanoma, with poor prognosis even in the era of immunotherapy. We present the case of a 37-year-old man who was diagnosed with stage IV melanoma with lymphonodular, splenic and pulmonary metastases. Treatment with dabrafenib and trametinib led to a complete remission, but subsequent symptomatic LMD. Treatment was changed to intrathecal methotrexate, leading to aseptic meningitis, but also a remission of LMD. Followed by ipilimumab monotherapy, a durable, complete remission was observed. Symptomatic LMD may not be amenable to immunotherapy alone, as quick responses may be needed. With little evidence and few retrospective trials demonstrating the challenging treatment of LMD, intrathecal chemotherapy, potentially in combination, may still be considered a viable option.