This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Medicine
The treatment for CNS leukaemia is 
Select and explain. 
A. Intrathecal methotrexate, B. Vincristine and prednisolone, C. Intrathecal vincristine, D. IV prednisolone
A: Intrathecal methotrexate
Answer: A: Intrathecal methotrexate 
Explanation: Intrathecal methotrexate is a chemotherapy drug which is given to prevent leukaemia cells entering the cerebrospinal fluid (CSF) around the spine and brain. This drug is also used to treat leukaemia found in the CSF for CNS leukemias Ref Davidson 23rd edition pg 788