Effect of brain irradiation on blood-CSF barrier permeability of chemotherapeutic agents.

Effect of irradiation on blood-cerebrospinal fluid (CSF) barrier (BCB) was studied quantitatively by observing the effect of methotrexate (MTX) permeation into the CSF before, during, and after brain irradiation after i.v. injection of MTX. Observation of 15 brain tumor patients indicated that in large brain tumors, the BCB was seriously damaged; in small tumors, the BCB would gradually open. Compared with the findings before irradiation, the increase of permeability of MTX was zero to threefold. It is thus advisable to give chemotherapy only after 20 Gy of irradiation.