Emergent radiation for leukemic optic nerve infiltration in a child receiving intrathecal methotrexate.

Vision loss caused by leukemic infiltration of the optic nerve is an oncologic emergency. To maintain vision, radiotherapy must be initiated quickly. However, many pediatric acute lymphoblastic leukemia (ALL) patients with ophthalmic and central nervous system (CNS) relapse receive intrathecal methotrexate and/or cytarabine. Conflicting reports about intrathecal therapy potentiating radiation toxicity complicate decision-making. Here we present a teaching case to illustrate the safety and effectiveness of radiotherapy, even in the setting of concurrent intrathecal treatment. The patient was a 22-month-old female with CNS relapse of ALL, presenting with new funduscopic evidence of left optic nerve infiltration, and MRI evidence of bilateral involvement. Her optic nerve disease was progressing through systemic induction chemotherapy and intrathecal cytarabine, hydrocortisone, and methotrexate. We proceeded with emergent simulation and treatment under general anesthesia, targeting the bilateral posterior orbits (retinae), optic nerves, optic chiasm, and given clinical concern for possible partial third nerve palsy, the cavernous sinus. Treatment with 12 Gy in 6 daily fractions was administered. Neuro-ophthalmology evaluation 1.5 months later found worsening left vision, but her right vision and funduscopic exam remained normal along with normal MRI findings on the right. Six months after undergoing treatment, she was doing well after undergoing allogeneic bone marrow transplant. This case illustrates important teaching points for leukemic optic nerve infiltration: radiotherapy should be initiated immediately to restore/maintain vision, and the literature suggests that, even in the setting of intrathecal chemotherapy, ophthalmic radiation may be safe and effective.