Radiotherapy vs intrathecal chemotherapy for CNS prophylaxis in childhood ALL.

Prophylaxis of the central nervous system against meningeal leukemia is a complex problem. There is no optimal solution that is universal for all patients. Instead, treatment must be individualized for the patient's age, prognostic group, and the concomitant systemic chemotherapy. Radiation, because of its CNS toxicity and potential carcinogenicity, is reserved for those in the highest risk groups. For these patients, 1,800 cGy cranial radiation plus intrathecal methotrexate during induction, consolidation, and maintenance therapy is recommended. For other patients, protection should be limited to systemic and intrathecal chemotherapy. Further studies are needed to compare the most effective intrathecal methotrexate prophylaxis with triple intrathecal drug therapy.