Intracranial tumours

Intracranial tumours represent about 2% of all cancers. There are no known risk factors apart from prior irradiation to the skull and brain and a few rare neurogenetic syndromes, e.g. neurofibromatosis, von Hippel–Lindau syndrome, Li–Fraumeni syndrome. They may be intrinsic or extrinsic, which determines potential resectability. Neuroepithelial tumours (predominantly gliomas) account for 50 to 60% of all primary tumours. Recent discovery of IDH mutations in low-grade gliomas and secondary glioblastoms as an important indicator of favourable prognosis. 50% of secondary tumours are from the lung. Increasing numbers of brain metastases from breast cancer due to prolonged survival from systemic disease.

Clinical features

Early neurological symptoms of intracranial tumours are non-specific. Typical manifestations include (1) progressive focal neurological deficit—typically subacute; present in over 50% of patients at time of diagnosis; (2) seizures—may be focal or secondarily generalized; the presenting symptom in 25 to 30% of patients with gliomas; (3) raised intracranial pressure—the classic picture of headache, vomiting, visual obscurations and papilloedema is easily recognized, but most patients present before this develops; and (4) altered mental state—cognitive and personality changes. More incidental tumours are now being discovered as a result of the increased availability of cranial imaging.

Diagnosis, treatment and prognosis

Diagnosis—this is made by a combination of CT/MRI scanning and pathological examination of either a biopsy or resection specimen. Genetic information relating to 1p19q, IDH, and MGMT methylation status is becoming increasingly important for guiding treatment and prognosis.

Treatment—the conventional methods are (1) surgery—may be curative for extrinsic tumours, but rarely so for intrinsic tumours; (2) radiotherapy—as primary or adjuvant treatment; (3) chemotherapy—concomitant treatment with temozolomide and radical radiotherapy followed by adjuvant temozolomide has improved survival in GBM; certain tumours may respond particularly well, e.g. oligodendrogliomas with chromosome 1p/19q deletion. (4) biological agents—anti-angiogenic agents are being used for relapsed malignant gliomas but their effect on overall survival has not been proven.

Prognosis—this is determined by age at presentation (young > old), performance status (high > low), histological grade (low > high), and genetic mutations (1p19q, IDH mutation). As a general rule, survival with GBM (glioblastoma multiforme) is 1 to 2 years, anaplastic gliomas 2 to 5 years, and low-grade gliomas 5 to 15 years. Benign tumours such as meningiomas and pituitary adenomas have over 90% 10-year survival if diagnosed before irreversible neurological damage has occurred.