 The decision regarding which treatment patients receive is made randomly. Neither them or their doctor can select which treatment the patient will receive. There is reason to believe that both of these doses may benefit treating your brain tumor. After 6 months of chemotherapy, and assuming the brain tumor has not shown any sign of growth, they will begin receiving cis-retinoic acid. Cis retinoic acid has been shown in one study to possibly prevent or delay tumor recurrence. 