Chao E C
MathSoft, Inc., Seattle, Washington 98109, USA.
Biometrics. 1998 Mar;54(1):350-66.
Many researchers use the 5-year survival probability as a measurement of cure for long-term survival data. In addition to this probability, a mixture model with possibility of cure provides a predictive probability of cure given that a patient has survival to a period of time. Such probabilities are more realistic in measuring the effectiveness of the treatment and predicting the long-term survival of the patient than the 5-year survival rate. An extension of the cure model to the competing risks data is developed. The extended model is a finite mixtures model, where the independence of cause-specific failure times is not assumed. A data set consisting of leukemia with bone marrow transplant is used for illustration. Patients have three possible statuses after transplant: cured by the treatment, relapse of leukemia, or non-relapse-related death. Only the last two events are observable. Patients observed with these endpoints are uncensored cases and the transplant is not successful for them. A case is censored if the case is relapse-free and still alive at the end of its follow-up. Only censored cases have the possibility of being cured, but cure is not assumed to be observable. The status of cure is imputed by the posterior predictive probability of cure given the lifetime and is implemented in the Gibbs sampling. Cure is defined by assuming the risk for failure of a cured patient to be approximately zero. The probability of cure for the leukemia patients after the bone marrow transplant is about 27% for patients with the acute graft-versus-host disease (GVHD) and 46% for the non-GVHD group. The probability of relapse, given that one is not cured, is 0.50 for the non-GVHD group and 0.34 for the GVHD group. The non-GVHD group has a better chance of survival, while the GVHD group has a lower chance for relapse. This is known as the GVHD-versus-leukemia effect.
许多研究人员将5年生存概率作为长期生存数据治愈情况的一种衡量指标。除了这种概率外，具有治愈可能性的混合模型可提供在患者存活至某一时间段时的治愈预测概率。与5年生存率相比，此类概率在衡量治疗效果和预测患者长期生存方面更为现实。已开发出将治愈模型扩展到竞争风险数据的方法。扩展模型是一个有限混合模型，其中不假定特定病因的失效时间相互独立。使用一个由骨髓移植白血病数据集进行说明。移植后患者有三种可能状态：经治疗治愈、白血病复发或与复发无关的死亡。只有最后两个事件是可观察到的。观察到这些终点的患者为未删失病例，且移植对他们来说不成功。如果病例在随访结束时无复发且仍存活，则该病例被删失。只有删失病例有可能被治愈，但治愈情况不假定为可观察到的。治愈状态通过给定生存期的治愈后验预测概率进行估算，并在吉布斯抽样中实现。通过假定治愈患者的失败风险近似为零来定义治愈。骨髓移植后白血病患者的治愈概率，对于患有急性移植物抗宿主病（GVHD）的患者约为27%，对于非GVHD组患者约为46%。对于未治愈的患者，非GVHD组的复发概率为0.50，GVHD组为0.34。非GVHD组有更好的生存机会，而GVHD组复发机会较低。这就是所谓的GVHD与白血病效应。
