Gil Fabian, Miranda-Filho Adalberto, Uribe-Perez Claudia, Arias-Ortiz N E, Yépez-Chamorro M C, Bravo L M, de Vries Esther
PhD Program in Clinical Epidemiology, Department of Clinical Epidemiology and Biostatistics, Pontificia Universidad Javeriana, Bogotá, Colombia.
Department of Clinical Epidemiology and Biostatistics, Faculty of Medicine, Pontificia Universidad Javeriana, Bogotá, Colombia.
J Cancer Epidemiol. 2022 Jan 30;2022:9068214. doi: 10.1155/2022/9068214. eCollection 2022.
Estimation of survival requires follow-up of patients from diagnosis until death ensuring complete and good quality data. Many population-based cancer registries in low- and middle-income countries have difficulties linking registry data with regional or national vital statistics, increasing the chances of cases lost to follow-up. The impact of lost to follow-up cases on survival estimates from small population-based cancer registries (<500 cases) has been understudied, and bias could be larger than in larger registries.
We simulated scenarios based on idealized real data from three population-based cancer registries to assess the impact of loss to follow-up on 1-5-year overall and net survival for stomach, colon, and thyroid cancers-cancer types with very different prognosis. Multiple scenarios with varying of lost to follow-up proportions (1-20%) and sample sizes of (100-500 cases) were carried out. We investigated the impact of excluding versus censoring lost to follow-up cases; punctual and bootstrap confidence intervals for the average bias are presented.
Censoring of lost to follow-up cases lead to overestimation of the overall survival, this effect was strongest for cancers with a poor prognosis and increased with follow-up time and higher proportion of lost to follow-up cases; these effects were slightly larger for net survival than overall survival. Excluding cases lost to follow-up did not generate a bias on survival estimates on average, but in individual cases, there were under- and overestimating survival. For gastric, colon, and thyroid cancer, relative bias on 5-year cancer survival with 1% of lost to follow-up varied between 6% and 125%, 2% and 40%, and 0.1% and 1.0%, respectively.
Estimation of cancer survival from small population-based registries must be interpreted with caution: even small proportions of censoring, or excluding lost to follow-up cases can inflate survival, making it hard to interpret comparison across regions or countries.
生存估计需要对患者从诊断到死亡进行随访，以确保获得完整且高质量的数据。低收入和中等收入国家的许多基于人群的癌症登记处难以将登记数据与地区或国家生命统计数据相联系，增加了失访病例的可能性。对于基于小人群的癌症登记处（<500例病例），失访病例对生存估计的影响研究不足，且偏差可能比大型登记处更大。
我们基于来自三个基于人群的癌症登记处的理想化真实数据模拟场景，以评估失访对胃癌、结肠癌和甲状腺癌（预后差异很大的癌症类型）1至5年总生存和净生存的影响。进行了多种失访比例（1%至20%）和样本量（100至500例病例）不同的场景模拟。我们研究了排除与截尾失访病例的影响；给出了平均偏差的即时和自助置信区间。
截尾失访病例会导致总生存的高估，这种效应在预后较差的癌症中最为明显，并随随访时间和失访病例比例的增加而增加；这些效应在净生存中比总生存略大。排除失访病例平均不会对生存估计产生偏差，但在个别情况下，存在生存估计低估和高估的情况。对于胃癌、结肠癌和甲状腺癌，失访率为1%时，5年癌症生存的相对偏差分别在6%至125%、2%至40%和0.1%至1.0%之间。
从小规模基于人群的登记处估计癌症生存时必须谨慎解释：即使是很小比例的截尾或排除失访病例也可能夸大生存情况，使得难以解释不同地区或国家之间的比较结果。
