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Intrathecal chemotherapy with methotrexate or cytosine arabinoside is the standard approach to prophylaxis and treatment of central nervous system leukemia in children.
 potential therapeutic event: treatment 
Please tell me event type and its trigger word from given type options. Output format is "type: trigger".  Option: adverse event, potential therapeutic event 
Text: {0} 
Answer:
 potential therapeutic event: treatment 