Department of Neuroradiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
Neuroradiology. 2011 Aug;53(8):593-8. doi: 10.1007/s00234-010-0764-8. Epub 2010 Sep 17.
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.
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.
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.
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.
具有未经证实临床获益的新型线圈不断扩大血管内动脉瘤治疗的手段。由于需要大量患者才能发现此类新技术的益处，因此无法及时评估其疗效。我们提出将动脉瘤复发体积作为衡量线圈稳定性的替代终点。我们假设与传统的二分类终点研究相比，这种方法可以使用较小的样本量来检测新材料的效果。
获得机构审查委员会的批准和知情同意。共纳入 59 例患者，这些患者的动脉瘤体积逐渐缩小，并且至少有两次可供使用的时间飞越磁共振血管造影（time-of-flight magnetic resonance angiography，TOF-MRA）随访。使用新开发的基于 TOF-MRA 图像测量动脉瘤体积差异的软件。根据观察到的复发体积和再治疗率，计算了未来比较标准线圈与“新型线圈”的研究的样本量。
平均复发体积为 38.92 μl（SD110.85 μl）。为了在常规研究（二分类终点）中显示标准线圈与“新型线圈”相比，再治疗率降低 50%（p = 0.05；效能 80%），则需要 n = 356 个样本，而如果使用连续替代终点“复发体积”，则需要 n = 78 个样本。当将我们的数据外推到文献中给出的数据时，如果不损失统计效能，则样本量可从 n = 948 减少到 n = 74。
使用基于 TOF-MRA 的体积分析作为替代终点对新型材料进行进一步研究，可以大大减少样本量，并以较小的成本及时评估新材料的可能获益。
