Fractionated radiotherapy as first-line treatment for intracranial meningiomas

Abstract BACKGROUND Meningiomas are the most common primary brain tumour, and patients requiring intervention typically undergo surgical resection as first-line therapy. However, fractionated radiotherapy (fRT) as primary treatment remains an option for patients with larger tumours and surgical contraindications, although outcome prediction in this group remains uncertain. We aimed to assess the clinical factors that contribute to treatment failure in a cohort of meningiomas treated with fRT as first-line therapy. METHODS Patients treated with primary fRT for intracranial meningiomas at our institution from November 1, 1998 to December 30, 2017 were reviewed. Those who received upfront surgical resection, radiosurgery, or had less than 6 months of clinical follow up were excluded. We applied logistic regression and Cox regression analysis to ascertain key predictors of treatment failure, progression-free survival (PFS), and adverse events following radiotherapy. RESULTS Our cohort included 147 tumours, of which 25 progressed after fRT (median PFS of 3.45 years). Tumours that progressed following RT had a larger median gross tumour volume (GTV) than those that did not (32.3cm3 vs 20.2cm3,p = 0.03768). Pre-RT GTV greater than 11.27cm3 was independently predictive of treatment failure. Larger pre-RT GTV was also associated with significant (grade 3/4) adverse events following fRT. Finally, cerebellopontine angle meningiomas were more prevalent in the group that progressed (20% vs 3.3%, p = 0.0046), whereas cavernous sinus and optic nerve sheath meningiomas had longer PFS (p = 0.0067). CONCLUSION We present the largest known cohort of meningiomas treated with fRT as first line therapy and find pre-RT tumour GTV and location to be the critical predictors of outcome, adding to the discussion of treatment considerations in this heterogeneous disease.