Koscielny S, Thames H D
Department of Medical Statistics, Institut Gustave Roussy, Villejuif, France.
Cancer. 2001 Oct 15;92(8):2220-7. doi: 10.1002/1097-0142(20011015)92:8<2220::aid-cncr1566>3.0.co;2-v.
Several methods are used to estimate risks of local and distant failure after treatment of breast carcinoma. The authors' purpose was to present a physician-friendly description of the potential bias in these methods, and to suggest an improvement.
The cumulative incidence based on first event (cumulative incidence [CI]) and Kaplan-Meier method based on first (KM[1st]) or all (KM[any]) events, are applied to a database comprising 2521 women treated for breast carcinoma at the same institution and observed for more than 20 years. The authors relate these estimates to the region containing all possible estimates of failure rate. This region contains the "true" risk (net risk, or risk that would be observed in the absence of competing risks) of local or distant failure.
The CI estimate is the lowest possible estimate of the true failure rate. Under certain "commonsense" assumptions, the CI estimate is below the lowest possible estimate of risk of failure. The KM(1st) estimate is higher than the CI estimate and lower than the KM(any) estimate. Under the same commonsense assumptions, the KM(1st) method also underestimates the true failure rate.
Methods based on time to first event such as CI and KM(1st) underestimate the true risk. In the design of clinical trials, consideration should be given to longer follow-up and the KM(any) method of analyzing results because it provides a less biased estimate.
有几种方法可用于估计乳腺癌治疗后局部和远处复发的风险。作者的目的是对这些方法中潜在的偏差进行便于医生理解的描述，并提出改进建议。
基于首次事件的累积发病率（累积发病率[CI]）以及基于首次（KM[1st]）或所有（KM[any]）事件的Kaplan-Meier方法，应用于一个包含2521名在同一机构接受乳腺癌治疗并随访超过20年的女性的数据库。作者将这些估计值与包含所有可能失败率估计值的区域相关联。该区域包含局部或远处复发的“真实”风险（净风险，即在没有竞争风险的情况下观察到的风险）。
CI估计值是真实失败率的最低可能估计值。在某些“常识性”假设下，CI估计值低于失败风险的最低可能估计值。KM(1st)估计值高于CI估计值且低于KM(any)估计值。在相同的常识性假设下，KM(1st)方法也低估了真实失败率。
基于首次事件时间的方法，如CI和KM(1st)，低估了真实风险。在临床试验设计中，应考虑更长时间的随访以及采用KM(any)方法分析结果，因为它提供的偏差较小的估计值。
