452 Novel in vivo imaging of acute chemotherapy-induced vascular toxicity

Abstract

To estimate the maximum-tolerated dose (MTD); study the pharmacology of escalating doses of gefitinib combined with radiation therapy in patients ⩽21 years with newly diagnosed intrinsic brainstem gliomas (BSG) and incompletely resected supratentorial malignant gliomas (STMG); and to investigate epidermal growth factor receptor (EGFR) amplification and expression in STMG.Three strata were identified: stratum 1A – BSG; stratum IB – incompletely resected STMG not receiving enzyme-inducing anticonvulsant drugs (EIACD); and stratum II – incompletely resected STMG receiving EIACD. Dose escalation using a modified 3 + 3 cohort design was performed in strata IA and II. The initial gefitinib dosage was 100 mg/m2/d commencing with radiation therapy and the dose-finding period extended until 2 weeks post-radiation. Pharmacokinetics (PK) and biology studies were performed in consenting patients.Of the 23 eligible patients, 20 were evaluable for dose-finding. MTDs for strata IA and II were not established as accrual was halted due to four patients experiencing symptomatic intratumoral haemorrhage (ITH); two during and two post dose-finding. ITH was observed in 0 of 11 patients treated at 100 mg/m2/d, 1 of 10 at 250 mg/m2/d and 3 of 12 at 375 mg/m2/d. Subsequently a second patient at 250 mg/m2/d experienced ITH. PK analysis showed that the median gefitinib systemic exposure increased with dosage (p = 0.04). EGFR was over-expressed in 5 of 11 STMG and amplified in 4 (36%) samples.This trial provides clear evidence of EGFR amplification in a significant proportion of paediatric STMG and 250 mg/m2/d was selected for the phase II trial.