While growth factors exist to support patients with treatment-induced neutropenia and anemia, treatment-induced thrombocytopenia remains a problem and often causes treatment delays and dose reductions and requires platelet transfusions. Toxicities such as marrow fibrosis, thromboembolic events and rebound thrombocytopenia may further complicate the already complex management of cancer patients. We report the first use of eltrombopag for radiation-induced thrombocytopenia in a brain tumor patient. A 66 year old male with a history of chronic low back pain for years presented with increasing low back pain radiating down his right leg, paresthesias and increasing right lower extremity weakness for 4 months. Spine imaging revealed an enhancing L1-2 intramedullary lesion (Fig. 1a). He underwent a T12-L3 laminectomy and excision of this lesion. The pathological diagnosis revealed a glioblastoma. Subsequent imaging of the brain and spine revealed widely disseminated disease within the neuroaxis including a large splenial lesion (Fig. 1b) and drop metastases throughout cervical, thoracic and lumbosacral spine (Fig. 1c). We treated his craniospinal axis to a dose of 3600 cGy, 20 fractions of 180 cGy each, followed by a conedown field to T12 to L3 for an additional 900 cGy, total dose to T12-L3 was 4500 cGy, and a partial brain field to his bulky brain disease for an additional 2340 cGy, total dose 5940 cGy. However, due to concerns over myelosuppression, we decided to forego concurrent temozolomide. At the start of radiation, his pre-treatment baseline platelet count was 132,000 ll. During radiation, his platelets achieved nadir at 44,000 ll on day #19 and then stabilized between 57,000 and 73,000 ll for the remaining 5 weeks of radiation. Following completion of radiation, persistent moderate thrombocytopenia precluded our ability to start myelosuppressive chemotherapy. To date, there is no approved growth factor for support of patients with radiationor chemotherapy-induced thrombocytopenia. As part of our evaluation of our patient’s thrombocytopenia and prior to initiating treatment with eltrombopag (a nonpeptide thrombopoietin receptor agonist), we obtained a splenic ultrasound that ruled out splenomegaly, and a bone marrow biopsy revealed a hypocellular marrow with decreased megakaryocytes consistent with radiation effect (fields of CSI extended down to end of thecal sac & sacrum, laterally to sacroiliac joints). There was no evidence or suggestion of other drug reaction e.g. (heparin induced thrombocytopenia) or autoimmune phenomenon (e.g. ITP) to explain the findings. After registering through the Promacta Cares program (GlaxoSmithKline), he began treatment with eltrombopag at 50 mg po daily. Upon initiation of eltrombopag, his platelet count was 72,000 . After starting treatment with eltrombopag, his platelets reached 116,000 at 1 week, J. P. Duic (&) J. Grewal K. McConie Long Island Brain Tumor Center at Neurological Surgery, P.C. 600 Northern Blvd Suite 113, Great Neck, NY 11021, USA