Salukhe Tushar V, Dimopoulos Konstantinos, Sutton Richard, Coats Andrew J, Piepoli Massimo, Francis Darrel P
National Heart and Lung Institute, College of Science, Technology and Medicine, London, UK.
Circulation. 2004 Apr 20;109(15):1848-53. doi: 10.1161/01.CIR.0000125522.10053.29. Epub 2004 Apr 5.
Although treatment benefit in randomized controlled trials of defibrillators is often summarized by the numbers of lives saved (absolute risk difference), this may not be a good representation of what matters most to patients, namely, the amount of life they should expect to gain from implantation. The estimate of gain in life-years may depend on duration of follow-up. In this study, we examine this dependency.
We estimated, from published data of 8 landmark defibrillator trials, the cumulative benefit in life-years gained at time points from 3 months to 3 years. Because the trial populations, clinical status, and prognosis varied widely between studies, we expressed for each study the benefit at each time point as the proportion of benefit at 3 years. The average dependency of the benefit on duration of follow-up was then calculated. We found that the number of life-years gained from 1 device implantation increases with length of follow-up considered. Importantly, this increase is markedly nonlinear. Within the 3-year span addressable, the benefit rises with the square of time (gain infinity t(1.94), R2=0.998, P<0.001).
Measurable benefit from a defibrillator to patients' life spans (life-years gained) is dramatically dependent on the time window over which the benefit is assessed. Because the effort of implantation is front loaded, yet benefit grows with time, the choice of an early time point artificially reduces apparent benefit and artificially increases the apparent number needed to treat to prevent an event. These are useful considerations for the formulation of treatment policy (and even for planning of the follow-up phase of clinical trials).
尽管除颤器随机对照试验中的治疗益处通常用挽救的生命数量（绝对风险差异）来概括，但这可能无法很好地体现对患者最重要的因素，即他们预期从植入中获得的生命时长。生命年增益的估计可能取决于随访时间。在本研究中，我们对这种依赖性进行了研究。
我们根据8项具有里程碑意义的除颤器试验的已发表数据，估计了从3个月到3年各时间点获得的累积生命年益处。由于各研究之间的试验人群、临床状况和预后差异很大，我们将每项研究在每个时间点的益处表示为3年时益处的比例。然后计算益处对随访时间的平均依赖性。我们发现，从1次设备植入中获得的生命年数随着所考虑的随访时间长度而增加。重要的是，这种增加明显是非线性的。在可处理的3年时间跨度内，益处随时间的平方增加（增益∞t(1.94)，R2 = 0.998，P < 0.001）。
除颤器对患者寿命（获得的生命年数）的可测量益处极大地取决于评估益处的时间窗口。由于植入的努力是前期投入的，但益处随时间增长，选择早期时间点会人为降低明显的益处，并人为增加预防事件所需治疗的明显数量。这些对于制定治疗政策（甚至对于规划临床试验的随访阶段）都是有用的考虑因素。
