Ganesh B, Swaminathan R, Mathew A, Sankaranarayanan R, Hakama M
Division of Hospital Cancer Registry and Biostatistics, Tata Memorial Centre, Mumbai, India.
IARC Sci Publ. 2011(162):15-21.
This chapter presents formulae that methodologically adjust for losses, and gives examples describing magnitude of bias in survival estimates without such adjustment. Loss-adjusted survival is estimated under the assumption that survival of patients Lost to follow-up is the same as that for patients with known follow-up time and similar characteristics of different prognostic factors at first entry. The observed number of Losses to follow-up is then relocated into expected numbers of death and survivors on this basis. Standard methods, such as the actuarial one, are then applied with the sum of observed and expected outcome events. A total of 336 hospital series of treated new breast cancer cases from Mumbai with 24% lost to follow-up revealed a substantial bias of 7 per cent units for 3-year survival estimated with (54%) and without (61%) loss-adjustment. Stepwise adjustment of losses established that increasing the number of prognostic factors explained the bias better. Population-based series comprising 13 371 cases of top ranking cancers from Chennai, with loss to follow-up ranging from 7-24%, revealed negligible bias, ranging from 0-2% in 5-year survival by the loss-adjusted approach for different cancers. Data source seems to affect the need for loss-adjustment, and the loss-adjusted approach is recommended when hospital-based cancer registry data of a low- or medium-resource country are used to evaluate the outcome of cancer patients.
本章介绍了从方法学上对失访情况进行调整的公式，并给出了一些例子，描述了在未进行这种调整的情况下生存估计中的偏倚程度。失访调整后的生存率是在以下假设下估计的：失访患者的生存率与随访时间已知且初次就诊时不同预后因素特征相似的患者的生存率相同。然后，根据这一假设，将观察到的失访人数重新分配为预期的死亡人数和存活人数。接着，将观察到的和预期的结局事件之和应用标准方法，如精算方法。孟买共有336个治疗新乳腺癌病例的医院系列，其中24%失访，结果显示，采用（54%）和未采用（61%）失访调整估计的3年生存率存在7个百分点的显著偏倚。逐步调整失访情况表明，增加预后因素的数量能更好地解释这种偏倚。钦奈的13371例顶级癌症病例组成的基于人群的系列，失访率在7%-24%之间，结果显示，通过失访调整方法，不同癌症的5年生存率偏倚可忽略不计，在0%-2%之间。数据来源似乎会影响失访调整的必要性，当使用低资源或中等资源国家基于医院的癌症登记数据来评估癌症患者的结局时，建议采用失访调整方法。
