Abstract
Introduction
New coils with unproven clinical benefit enlarge the armamentarium for endovascular aneurysm treatment continuously. Large patient numbers needed to detect benefits of such new techniques prevent timely evaluation of efficacy. We propose measuring the volume of aneurysm recurrences as surrogate endpoint for coil stability. We hypothesize that this method allows detecting effects of new materials with reduced sample sizes in comparison to conventional studies with dichotomous endpoints.
Methods
Institutional review board approval and informed consent were obtained. Fifty-nine patients with decreasing aneurysm size and at least two available follow-up time-of-flight magnetic resonance angiographies (ToF-MRAs) were included. Newly developed software for measuring aneurysm volume differences based on ToF-MRA images was used. Based on the observed recurrence volumes and retreatment rates, the sample size for future studies comparing standard versus “new coils” were calculated.
Results
Mean recurrence volume was 38.92 μl (SD110.85 μl). To show a 50% reduction of retreatment rate to control (p = 0.05; power 80%) in a regular study (dichotomous endpoint), the required sample size would be n = 356 compared with n = 78 if using the continuous surrogate endpoint “recurrence volume”. When extrapolating our data to data given in the literature, sample sizes could be reduced from n = 948 to n = 74 without loss of statistical power.
Conclusion
Further studies on new materials using volumetric analysis based on ToF-MRA as surrogate endpoint could substantially decrease sample size and allow a more timely assessment of possible benefit of new materials with a fraction of the cost.
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References
Boet R, Wong G, Poon W, Lam J, Yu S (2005) Aneurysm recurrence after treatment of paraclinoid/ophthalmic segment aneurysms—a treatment-modality assessment. Acta Neurochir (Wien) 147:611–616
Campi A, Ramzi N, Molyneux AJ et al (2007) Retreatment of ruptured cerebral aneurysms in patients randomized by coiling or clipping in the International Subarachnoid Aneurysm Trial (ISAT). Stroke 38:1538–1544
Sluzewski M, van Rooij WJ, Rinkel GJ, Wijnalda D (2003) Endovascular treatment of ruptured intracranial aneurysms with detachable coils: long-term clinical and serial angiographic results. Radiology 227:720–724
Ries T, Siemonsen S, Thomalla G, Grzyska U, Zeumer H, Fiehler J (2007) Long-term follow-up of cerebral aneurysms after endovascular therapy prediction and outcome of retreatment. AJNR Am J Neuroradiol 28:1755–1761
White PM, Raymond J (2009) Endovascular coiling of cerebral aneurysms using “bioactive” or coated-coil technologies: a systematic review of the literature. AJNR Am J Neuroradiol 30:219–226
Raymond J, Guilbert F, Weill A et al (2003) Long-term angiographic recurrences after selective endovascular treatment of aneurysms with detachable coils. Stroke 34:1398–1403
Byrne JV, Sohn MJ, Molyneux AJ, Chir B (1999) Five-year experience in using coil embolization for ruptured intracranial aneurysms: outcomes and incidence of late rebleeding. J Neurosurg 90:656–663
Slob MJ, Sluzewski M, van Rooij WJ, Roks G, Rinkel GJ (2004) Additional coiling of previously coiled cerebral aneurysms: clinical and angiographic results. AJNR Am J Neuroradiol 25:1373–1376
Molyneux A, Kerr R, Yu L et al (2005) International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet 366:809–817
Cloft HJ (2007) Hydrocoil for endovascular aneurysm occlusion (HEAL) study: 3–6 month angiographic follow-up results. AJNR Am J Neuroradiol 28:152–154
Gallas S, Pasco A, Cottier JP et al (2005) A multicenter study of 705 ruptured intracranial aneurysms treated with Guglielmi detachable coils. AJNR Am J Neuroradiol 26:1723–1731
Bandeira A, Raphaeli G, Baleriaux D, Bruneau M, De Witte O, Lubicz B (2010) Selective embolization of unruptured intracranial aneurysms is associated with low retreatment rate. Neuroradiology 52:141–146
Fiehler J, Byrne JV (2009) Factors affecting outcome after endovascular treatment of intracranial aneurysms. Curr Opin Neurol 22:103–108
White PM, Lewis SC, Nahser H, Sellar RJ, Goddard T, Gholkar A (2008) Hydrocoil endovascular aneurysm occlusion and packing study (HELPS trial): procedural safety and operator-assessed efficacy results. AJNR Am J Neuroradiol 29:217–223
Linfante I, DeLeo MJ 3rd, Gounis MJ, Brooks CS, Wakhloo AK (2009) Cerecyte versus platinum coils in the treatment of intracranial aneurysms: packing attenuation and clinical and angiographic midterm results. AJNR Am J Neuroradiol 30:1496–1501
Roy D, Milot G, Raymond J (2001) Endovascular treatment of unruptured aneurysms. Stroke 32:1998–2004
Bhandari M, Lochner H, Tornetta P 3rd (2002) Effect of continuous versus dichotomous outcome variables on study power when sample sizes of orthopaedic randomized trials are small. Arch Orthop Trauma Surg 122:96–98
Kwee TC, Kwee RM (2007) MR angiography in the follow-up of intracranial aneurysms treated with Guglielmi detachable coils: systematic review and meta-analysis. Neuroradiology 49:703–713
Ries T, Wulff A, Wegscheider K, Fiehler J (2010) Unexpected kink in aneurysm recurrence volume distribution is associated with retreatment decision. Neuroradiology 52:657–658
Acknowledgements
This work was supported by the Deutsche Forschungsgemeinschaft (Fi 904/5-1).
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We declare that we have no conflict of interest.
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Ries, T., Wegscheider, K., Wulff, A. et al. Quantification of recurrence volumes after endovascular treatment of cerebral aneurysm as surrogate endpoint for treatment stability. Neuroradiology 53, 593–598 (2011). https://doi.org/10.1007/s00234-010-0764-8
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DOI: https://doi.org/10.1007/s00234-010-0764-8