Single- Versus Multiple-Fraction Stereotactic Radiotherapy

Although surgical excision is the treatment of choice for accessible skull base meningiomas, a significant subset of complex tumours tightly attached to or encasing neurovascular structures cannot be removed safely via surgery alone. In patients with residual or progressing disease after incomplete tumour resection, adjuvant external beam radiation therapy (RT) has traditionally been employed, with a reported local tumour control rate of up to 90% at 10 years. In recent decades, RT has evolved to encompass conformal and stereotactic techniques. The dramatic technical advances in all aspects of treatment have led to better immobilization, imaging, planning, and treatment. Advanced radio-oncology techniques include intensity-modulated radiotherapy (IMRT), volumetric arc therapy (VMAT), and stereotactic radiotherapy (SRT) and radiosurgery (SRS), which allow for more precise dose delivery to the tumour while limiting the amount of radiation to the sensitive brain structures, i.e. the optic pathway and the brainstem. New radiation techniques, particularly SRS, have progressively emerged as effective primary treatments for selected meningiomas of the skull base. Large series demonstrate local control rates of over 90% at 5 years following SRS, and above 80% at 10–15 years. Although virtually non-invasive, SRS carries a risk of late radiation-induced toxicity, typically cranial nerve deficits causing impaired visual acuity and ocular motility. For patients with large skull base meningiomas or tumours in close proximity to the optic pathway, fractionated SRS (2–5 fractions) has emerged as an alternative to single-fraction SRS, with the hope of reducing the long-term consequences of treatment while maintaining its effectiveness. Currently, SRT and SRS are an essential part of the modern management of skull base meningiomas recurring after surgery or in difficult-to-access locations.