INNV-18. RECURRENT SHH MEDULLOBLASTOMA EXTRANEURAL METASTASES TO THE BONE MARROW WITHOUT CNS INVOLVEMENT

Abstract

Abstract Medulloblastoma is the most common primary brain tumor in children, but is rare in adults. Because of the scarcity of adult medulloblastoma cases, treatment guidelines in the adult population are not well established, especially regarding surveillance and treatment of recurrent disease. A 47-year-old African American male presented with one month of progressive unsteady gait and dizziness. Imaging revealed a posterior fossa mass and the patient underwent gross total resection. Histology confirmed medulloblastoma and molecular subtyping revealed Sonic Hedgehog (Shh) pathway activation. No metastases were found at the time of diagnosis, and the patient received adjuvant craniospinal radiation therapy. Three years later the patient developed low back pain with severe sciatica affecting his gait and pancytopenia. Imaging revealed diffuse osseous disease without CNS recurrence and bone marrow biopsy confirmed recurrent medulloblastoma. The patient subsequently began reduced chemotherapy consisting of cisplatin and etoposide because of his severe pancytopenia. Due to a lack of response after 4 cycles, the SMO antagonist vismodegib was added. Follow-up imaging revealed improvement/stability of osseous disease, lab work demonstrated resolution of pancytopenia, and repeat bone marrow was without malignancy. Vismodegib was continued as maintenance therapy. Six months after completion of cisplatin/etoposide, follow-up imaging revealed progression of metastatic disease. Shh activated medulloblastomas have demonstrated responses to SMO inhibition. However, these responses are often transient secondary to rapid development of resistance, but may have a role to play in patients who have bone marrow involvement that limits use of cytotoxic therapy or bone marrow transplant. Due to poor survival outcomes associated with bone marrow metastases, aggressive screening for bone marrow metastases at diagnosis and in surveillance should be considered.