Management decisions on unruptured intracranial aneurysms before and after implementation of the PHASES score

Background: In management decisions on saccular unruptured intracranial aneurysms (UIAs) the risk of rupture is an important factor. The PHASES score, introduced in 2014, provides absolute 5-year risks of rupture based on six easily retrievable patient and aneurysm characteristics. We assessed whether management decisions on UIAs changed after implementation of the PHASES score. Patient and methods: We included all patients with UIAs who were referred to two Dutch tertiary referral centers for aneurysm care in the Netherlands (University Medical Center Utrecht (UMCU) and Leiden University Medical Center (LUMC)) between 2011 and 2017. Analyses were done on an aneurysm level. We calculated the overall proportion of UIAs with a decision to treat before and after PHASES implementation and studied the influence of age and center on post-implementation management changes. Results: We included 623 patients with 803 UIAs. The proportion of UIAs with a decision to treat was 123/360 (34.2%) before and 117/443 (26.4%) after PHASES implementation (absolute risk difference: −7.8%; 95% CI: −14.1 to −1.4). The decision to treat was made at a higher median PHASES score after implementation (7 points (IQR 5;10) pre- versus 8 points (IQR 5;10) post-implementation; p = 0.14). The reduced proportion with a treatment decision after implementation was most pronounced in patients <50 years (−22.3%; 95% CI: −39.2 to −3.4) and was restricted to treatment decisions made at the UMCU (−10.6%; 95% CI: −18.5 to −2.5). Discussion and conclusions: Management of UIAs changed following implementation of the PHASES score, but the impact of PHASES implementation on treatment decisions differed across age subgroups and centers.