Study to Evaluate Eflornithine + Lomustine vs Lomustine in Recurrent Anaplastic Astrocytoma (AA) Patients

Inclusion Criteria: Patients must meet all of the following inclusion criteria to be eligible for participation in this study: * Surgical or biopsy-proven diagnosis of WHO grade 3 AA. * First AA tumor progression or recurrence ≤ 6 months prior to randomization based on MRI using T2 hyperintesity, gadolinium (Gd)-contrast enhancement, or both. To avoid enrollment of patients with glioblastoma, patients with Gd-contrast enhancing tumors will be eligible if there is no necrosis seen on MRI and any of the following criteria is true: 1. Gd-contrast lesion margins are not clearly defined, 2. Gd-contrast lesions are only measurable in one dimension, 3. Gd-contrast lesion has two perpendicular diameters less than 10 mm, 4. Gd-contrast lesion has two perpendicular diameters greater than 10 mm but less than 20 mm and lesion does not demonstrate central necrosis, 5. Recent histopathological confirmation of WHO grade 3 AA * Received EBRT and temozolomide chemotherapy prior to first tumor progression or recurrence of WHO Grade 3 AA. * Completion of EBRT ≥ 6 months prior to randomization. * A patient whose AA tumor has progressed or recurred and has had another surgical resection prior to randomization will be eligible if a) pathology review confirms AA, and b) post-surgical MRI demonstrates measurable tumor on T2 FLAIR. * Karnofsky Performance Status (KPS) score of ≥ 70. Exclusion Criteria: Patients who meet any of the following exclusion criteria are not eligible for study participation: * MRI defining progression is consistent with a diagnosis of glioblastoma or radiation necrosis. * Patients who are considered to be refractory to EBRT and temozolomide but who have not progressed. * Prior systemic therapy for recurrence of AA. * Presence of extracranial or leptomeningeal disease. * Prior lomustine use. * Any other clinical condition or prior therapy that, in the opinion of the Investigator, would make the patient unsuitable for the study. * Pregnant or breastfeeding.