We propose methods to determine the minimum number of subjects remaining at risk after which Kaplan-Meier survival plots for time-to-event outcomes should be curtailed, as, once the number remaining at risk drops below this minimum, the survival estimates are no longer meaningful in the context of the investigation. The size of the decrease of the Kaplan-Meier survival estimate S(t) at time t if one extra event should occur is considered in two ways. In the first approach, the investigator sets a maximum acceptable absolute decrease in S(t) should one extra event occur. In the second, a minimum acceptable number of subjects still at risk is calculated by comparing the size of the decrease in S(t) if an extra event should occur with the variability of the survival estimate had all subjects been followed to that time (confidence interval approach). We recommend calculating both limits for the number still at risk and then making an informed choice in the context of the particular investigation. We explore further how the amount of information actually available can assist in considering issues of data maturity for studies whose outcome of interest is a survival percentage at a particular time point. We illustrate the approaches with a number of published studies having differing sample sizes and censoring issues. In particular, one study was the subject of some controversy regarding how far in time the Kaplan-Meier plot should be extended. The proposed methods allow for limits to be calculated simply using the output provided by most statistical packages.

中文翻译：

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事件发生时间分析中的数据成熟度和后续性。

我们提出了一些方法来确定仍然处于危险中的最小对象数，之后应缩减事件发生时间的Kaplan-Meier生存图，因为一旦处于危险中的剩余数量降至该最小值以下，则生存估计就不再在调查中有意义。如果应该再发生一次额外事件，则在时间t处Kaplan-Meier生存估计值S（t）减少的大小可以通过两种方式来考虑。在第一种方法中，研究人员将在发生一个额外事件的情况下将S（t）设置为最大可接受的绝对降低。在第二种方法中，通过比较S（t）下降的大小（如果应发生额外事件）与在所有受试者均随访到那时的生存率估计值的可变性，来计算仍处于危险中的受试者的最小可接受数目（置信度）间隔方法）。我们建议计算仍处于危险中的人数的两个限制，然后在特定调查的背景下做出明智的选择。我们将进一步探讨实际可用的信息量如何帮助考虑感兴趣的结果为特定时间点生存率的研究的数据成熟度问题。我们通过大量具有不同样本量和审查问题的已发表研究来说明这些方法。尤其是，一项研究是关于应延长Kaplan-Meier图多长时间的一些争议的主题。所提出的方法允许简单地使用大多数统计软件包提供的输出来计算限值。