Andersson Therese M-L, Dickman Paul W, Eloranta Sandra, Lambe Mats, Lambert Paul C
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Stat Med. 2013 Dec 30;32(30):5286-300. doi: 10.1002/sim.5943. Epub 2013 Aug 23.
A useful summary measure for survival data is the expectation of life, which is calculated by obtaining the area under a survival curve. The loss in expectation of life due to a certain type of cancer is the difference between the expectation of life in the general population and the expectation of life among the cancer patients. This measure is used little in practice as its estimation generally requires extrapolation of both the expected and observed survival. A parametric distribution can be used for extrapolation of the observed survival, but it is difficult to find a distribution that captures the underlying shape of the survival function after the end of follow-up. In this paper, we base our extrapolation on relative survival, because it is more stable and reliable. Relative survival is defined as the observed survival divided by the expected survival, and the mortality analogue is excess mortality. Approaches have been suggested for extrapolation of relative survival within life-table data, by assuming that the excess mortality has reached zero (statistical cure) or has stabilized to a constant. We propose the use of flexible parametric survival models for relative survival, which enables estimating the loss in expectation of life on individual level data by making these assumptions or by extrapolating the estimated linear trend at the end of follow-up. We have evaluated the extrapolation from this model using data on four types of cancer, and the results agree well with observed data.
生存数据的一个有用的汇总指标是预期寿命，它通过获取生存曲线下的面积来计算。因某种癌症导致的预期寿命损失是一般人群的预期寿命与癌症患者的预期寿命之差。该指标在实际中很少使用，因为其估计通常需要对预期生存和观察到的生存进行外推。可以使用参数分布来外推观察到的生存情况，但很难找到一种能捕捉随访结束后生存函数潜在形状的分布。在本文中，我们基于相对生存进行外推，因为它更稳定可靠。相对生存定义为观察到的生存除以预期生存，死亡率类似物是超额死亡率。有人提出了在生命表数据中对相对生存进行外推的方法，即假设超额死亡率已降至零（统计治愈）或已稳定为常数。我们建议使用灵活的参数生存模型来进行相对生存分析，这使得能够通过做出这些假设或外推随访结束时估计的线性趋势，在个体水平数据上估计预期寿命损失。我们使用四种癌症的数据评估了该模型的外推情况，结果与观察到的数据吻合良好。
