Etoposide achieves potentially cytotoxic concentrations in CSF of children with acute lymphoblastic leukemia.

PURPOSE: Although epipodophyllotoxins are commonly used in contemporary treatment regimens for acute lymphoblastic leukemia (ALL), their potential role in CNS-directed therapy has received little attention. We prospectively studied 20 children during initial remission of ALL and 16 children at relapse to assess CSF penetration of etoposide.
METHODS: Simultaneous plasma and CSF concentrations were assessed at a median of 2.8 hours (range, 0.4 to 5.3) after an intravenous (i.v.) or oral dose in 41 paired samples.
RESULTS: Etoposide given at 300 mg/m2 i.v. to patients during first remission and at 50 or 25 mg/m2 orally to those in relapse resulted in median CSF levels of 0.175 mumol/L (range, .066 to 2.12), 0.011 mumol/L (range, .004 to .032), and 0.007 mumol/L (range, .003 to .014), respectively. The CSF etoposide concentration was > or = 10 nmol/L in 20 of 20, five of 10, and two of 11 courses following 300 mg/m2 i.v., 50 mg/m2 orally, and 25 mg/m2 orally, respectively, and was positively related to both the concurrent etoposide plasma concentration (R2 = .64) and to dose (R2 = .73). The median ratio of CSF to plasma concentration was 0.30% (range, 0.09% to 3.12%), which was not related to dose, plasma concentration, or time postdose at which samples were obtained, but was positively correlated with the CSF protein concentration (R2 = 0.43, P = .006). Both the absolute etoposide CSF concentrations (P = .008) and the ratio of CSF to plasma concentrations (P = .023) were higher among first-remission patients who had CSF leukemic blasts at diagnosis compared with those without CSF blasts.
CONCLUSION: Because etoposide concentrations as low as 10 nmol/L may be cytotoxic in vitro, prolonged daily oral low-dose (50 mg/m2) or conventional i.v. doses of etoposide may contribute to successful CNS-directed therapy in children with ALL.