Surveillance of Unruptured Intracranial Aneurysms

Abstract

Background and Objectives:No consensus exists on adequate surveillance of conservatively managed unruptured intracranial aneurysms (UIAs). We aimed to determine optimal MRI surveillance strategies for growth of UIAs using cost-effectiveness analysis. A secondary aim was to develop a clinical tool for personalizing UIA surveillance.Methods:We designed a microsimulation model from a health care perspective simulating 100,000 55-year old women to estimate costs and quality-adjusted life years (QALYs) over a lifetime horizon in the US, UK, and the Netherlands, using literature-derived model parameters. Country-specific costs and willingness-to-pay thresholds ($100,000/QALY for the US, £30,000/QALY for the UK, and €80,000/QALY for the Netherlands) were used. Lifetime costs and QALYs were annually discounted at 3% for the US, 3.5% for the UK, or 4% (costs) and 1.5% (QALYs) for the Netherlands. Strategies were: no follow-up surveillance, follow-up with MRI in the 1st and 5th year after UIA discovery, every 5 years, every 2 years, or annually, or immediate intervention (i.e., clipping or coiling). Using the microsimulation model, we developed a tool for personalizing UIA surveillance for men and women, with different ages and varying aneurysm characteristics. Uncertainty in the input parameters was modeled with probabilistic sensitivity analysis.Results:Among 55-year old women, 2,222 individuals in the US, 1,910 in the UK, and 2,040 in the Netherlands needed to undergo an annual MRI scan to prevent one case of subarachnoid hemorrhage per year. No surveillance MRI was most cost-effective in the US (in 47% of the simulations) and UK (in 54% of simulations), whereas annual MRI was most cost-effective in the Netherlands (in 53% of simulations). In the US and UK, annual surveillance or surveillance in the 1st and 5th year after discovery was cost-effective in patients <60 years and at increased risk of aneurysm growth. The optimal, personalized, surveillance strategies were summarized in a look-up table for use in clinical practice.Conclusion:Generally, US and UK physicians should refrain from assigning patients, particularly older patients and those with few risk factors for aneurysm growth or rupture, to frequent MRI surveillance. In the Netherlands, annual follow-up is generally most cost-effective.

Follow-up Imaging of Low-Risk Unruptured Intracranial Aneurysms

“…Because such real-world studies are impractical to conduct, we are forced to rely, to some extent, on good-quality simulation studies. Luckily, the study by Cras et al 2 seems to be one of such studies.…”

“…In the article published in this issue of Neurology ®, Cras et al 2 stated “No consensus exists on the optimal frequency and duration of such surveillance, or even whether surveillance should be performed at all. Besides the high costs involved, the need for a cost-effective surveillance strategy is further emphasized by the relatively low mean age of patients when UIAs are detected.” Although some people may prefer frequent and long-term surveillance for peace of mind, costly and poorly justified follow-up studies may also cause psychological, emotional, and financial burden on people.…”

“…The simulation study by Cras et al 2 had 2 main objectives: (1) model the most cost-effective surveillance strategy of people diagnosed with low-risk UIAs in the United States, United Kingdom, and the Netherlands and (2) develop a clinical tool that enables planning of a personalized UIA surveillance. For these purposes, the authors developed a microsimulation state-transition model (STM), which simulated a lifelong repeated scanning (noninvasive angiographies) of 100,000 people with UIAs living in the US, UK, and the Netherlands.…”

“…Although the presented models cannot be tested on a web server, it is fortunate that all data and the full model are available on request from the first author. 2…”

“…In brief, from the public health point of view, repeated (whatever time intervals) follow-up MRA of people with incidental UIAs that have been classified into a low risk of rupture category may not be justified in many countries for most people with UIAs because differences in effectiveness between strategies were found to be small, whereas differences in costs were found to be considerable according to the conclusion by the authors. 2 However, if the rupture risk was estimated to be 1% for nongrowing and 5% for growing UIAs, the optimal strategy was (a) MRA in the first and fifth years in the US was (ICER $87,362/QALY), (b) immediate treatment in the Netherlands (ICER €18,400/QALY), and (c) no follow-up imaging studies in the UK. It is important to keep in mind that the fundamental concept of this study was to estimate the best surveillance strategy for those incidental UIAs, which we believe are safe to follow-up (i.e., low risk of rupture) or leave untreated.…”