Neurofibromatosis Type 1 and Type 2 Associated Tumours: Current trends in Diagnosis and Management with a focus on Novel Medical Therapies

Abstract

Neurofibromatosis type 1 (NF1) and Neurofibromatosis type 2 (NF2) are distinct single gene disorders, which share a predisposition to formation of benign nervous system tumours due to loss of tumour suppressor function. Since identification of the genes encoding NF1 and NF2 in the early 1990s, significant progress has been made in understanding the biological processes and molecular pathways underlying tumour formation. As a result, identifying safe and effective medical approaches to treating NF1 and NF2-associated tumours has become a focus of clinical research and patient care in recent years. This thesis presents a comprehensive discussion of the complications of NF1 and NF2 and approaches to treatment, with a focus on key tumours in each condition. The significant functional impact of these disorders in children and young adults is illustrated, demonstrating the need for coordinated care from experienced multidisciplinary teams. Response of the first Australian patients offered novel medications under careful prospective monitoring for safety and efficacy, is described. The approach to treatment trials including principles of patient selection, rationale for candidate medication choices, and identification of appropriate outcome measures are outlined. Treatment response is assessed utilizing multiple criteria including radiologic response, functional status and patient reported outcomes. Tumours considered include plexiform neurofibromas in NF1, treated with the protein tyrosine kinase inhibitor imatinib, with limited benefit. In NF2, vestibular schwannomas were treated using the vascular endothelial growth factor inhibitor bevacizumab, showing definite benefit in a proportion of patients. Refinements in the clinical approach to NF-associated tumours are discussed, considering results from this early experience. Optimizing tumour surveillance prior to intervention, identifying the most potent yet tolerable agents for use, determining when medical therapy should be utilized in concert with surgical and other approaches, and establishing ways of stratifying individual risk of disease complications and likelihood of treatment benefit, remain important questions for the future.