TM1-5 Optimising observation strategies for incidentally discovered intracranial meningiomas

Objectives Develop a model to identify incidental meningiomas at risk of observation failure. Design Retrospective study (2007–2015). Subjects 385 patients. Mean age 62.6 years. Methods Observation failure was defined as: new symptoms, MRI progression (absolute growth rate 2 cm 3 /year or absolute growth rate 1 cm 3 /year +relative growth rate 30%/year) or loss of treatment options. A prognostic model was developed using MRI and patient comorbidity. Results Over a median of 36 months, 44 (10.9%) meningiomas failed observation. Median time to failure was 33 months. Model parameters were based on statistical and clinical considerations and included: increasing tumour size (HR=2.17 [95% CI=1.53–3.09], p Conclusions Most meningiomas remain clinically and radiologically stable. Stratifying follow-up according to risk-group has the potential to reduce the cost to healthcare.