Medical Oncology

A 26 year old man was diagnosed 3 years ago with acute myeloid leukemia (AML) after presenting with leukocytosis and fevers. The karyotype was der(1;7)(q10;p10) and next-generation sequencing showed mutation in KRAS codon 12. The patient was treated with conventional induction chemotherapy with daunorubicin 90 mg/m2/d x 3 and cytarabine 100 mg/m2/d x 7, and achieved remission. He then underwent transplant. One year ago he developed headache, fatigue and nausea. His blood counts were normal and on exam there was no evidence of leukemia cutis, and there were no focal neurological deficits. Marrow biopsy was normal with full donor chimerism. CSF showed an increased WBC with 77% blasts that are positive for CD45(dim), CD13, CD15 and CD56(dim), and very dim for CD117. He was treated with intrathecal chemotherapy serially until clearance for CNS relapse followed by donor lymphocyte infusion. Recurrence of CNS symptoms and abnormal cytology led to treatment with high-dose cytarabine, then radiation, and then high-dose methotrexate, then nivolumab on a clinical trial. He now presents with another CNS recurrence. The immunophenotype and genetics are as before. MRI is depicted (axial T2 FLAIR image and sagittal T1 sequence). How would you treat this patient?