Distribution of intrathecally administered ACNU in mongrel dogs: pharmacokinetics and quantitative autoradiographic study

Medulloblastoma in childhood: revisiting intrathecal therapy in infants and children

INTRODUCTION

Intrathecal chemotherapy is being explored in medulloblastoma in pre-school children as part of brain-sparing strategies and as an alternative to unacceptably neurotoxic cranio-spinal radiotherapy. The range of drugs suitable for this route of administration is restricted by the lack of research evidence of pharmacological suitability and efficacy of other drugs in medulloblastoma.

METHODS

Ideal clinical, biological, physicochemical and pharmaceutical properties for intrathecal administration were defined through literature review of pharmaceutical texts, Medline, Embase and consulting the manufacturers. A total of 126 chemotherapy agents were assessed against these criteria by searching the academic domain of pharmaceutical texts, computer databases and consultation with manufacturers.

RESULTS

Of the 126 candidate drugs, 99 were rejected because of documentation of their irritant nature, neurotoxicity and requirement for hepatic activation in standard pharmaceutical texts. Fifty were rejected for a single identifiable reason including, neurotoxicity (n = 24), irritant (n = 15), needs enzyme activation (n = 5), clinical evidence of intrathecal neurotoxicity (n = 4) and no evidence of tumour-specific efficacy (n = 2). Where two reasons were cited the justifications were: neurotoxic and irritant (n = 3) and needs activation and systemic administration results in equivalent concentration (n = 1). Twenty-seven drugs remained of which 12 were selected as eligible for further clinical investigation, and 15 were selected for further pre-clinical investigation.

CONCLUSIONS

The pre-determined criteria were not applicable, in their entirety, in the majority of drugs, due to lack of information in the academic domain, emphasising the importance of a more open approach for sharing basic drug information. The prioritised list of 12 candidate drugs for clinical trial and 15 for pre-clinical investigation justify that a concerted research effort in this area of practice is made.

A rat model of leptomeningeal human neoplastic xenografts

Leptomeningeal (LM) cancer spread from either a primary brain tumor or a systemic cancer is rapidly fatal. Current therapies are ineffective and highly toxic to normal nervous system tissues. A xenograft model of LM neoplasia in nude rats using a diversity of tumor cell types was established in order to evaluate new treatment strategies and to study the pharmacokinetics and biological effects of treatments administered into the subarachnoid space. Consistent leptomeningeal engraftment and progressive tumor growth was seen after intrathecal injection of 9 of 13 tumor cells lines, including 2 melanomas, 2 neuroblastomas, 2 medulloblastomas, 2 gliomas, and 1 breast cancer. Clinical signs ranged from steady weight loss commencing from the day after tumor implantation to absence of any signs for three weeks until the sudden occurrence of major neurological deficits or death. Pathologic examination showed only leptomeningeal tumor growth with some cell lines and severe parenchymal invasion with others. CSF cytology consistently demonstrated tumor cells in animals with LM disease. Cranial magnetic resonance (MR) following intravenous (i.v.) administration of a contrast agent revealed enhancing lesions one week following melanoma tumor implantation. Reliable ventricular puncture was demonstrated by radiography following intraventricular (IVent) injection of an iodinated contrast material. IVent instillation of saline, albumin, or antibodies did not provoke clinical toxicity or an inflammatory response.