Xu J L, Prorok P C
Biometry Branch, Division of Cancer Prevention and Control, National Cancer Institute, Bethesda, MD 20892, USA.
Stat Med. 1995 Dec 30;14(24):2715-25. doi: 10.1002/sim.4780142410.
The goal of screening programmes for cancer is early detection and treatment with a consequent reduction in mortality from the disease. Screening programmes need to assess the true benefit of screening, that is, the length of time of extension of survival beyond the time of advancement of diagnosis (lead-time). This paper presents a non-parametric method to estimate the survival function of the post-lead-time survival (or extra survival time) of screen-detected cancer cases based on the observed total life time, namely, the sum of the lead-time and the extra survival time. We apply the method to the well-known data set of the HIP (Health Insurance Plan of Greater New York) breast cancer screening study. We make comparisons with the survival of other groups of cancer cases not detected by screening such as interval cases, cases among individuals who refused screening, and randomized control cases. As compared with Walter and Stitt's model, in which they made parametric assumptions for the extra survival time, our non-parametric method provides a better fit to HIP data in the sense that our estimator for the total survival time has a smaller sum of squares of residuals.
癌症筛查项目的目标是早期发现和治疗，从而降低该疾病的死亡率。筛查项目需要评估筛查的真正益处，即生存期延长超过诊断进展时间（领先时间）的时长。本文提出一种非参数方法，基于观察到的总生存期（即领先时间与额外生存期之和）来估计筛查发现的癌症病例的领先时间后生存期（或额外生存期）的生存函数。我们将该方法应用于纽约市健康保险计划（HIP）乳腺癌筛查研究的著名数据集。我们将其与未通过筛查发现的其他癌症病例组的生存期进行比较，如间隔期病例、拒绝筛查者中的病例以及随机对照病例。与沃尔特和斯蒂特的模型相比，他们对额外生存期做了参数假设，我们的非参数方法在总生存时间估计值的残差平方和较小的意义上，能更好地拟合HIP数据。
