Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Cancer Registry of Norway, Institute of Population-Based Cancer Research, Oslo, Norway; Department of Research and Innovation, Møre and Romsdal Hospital Trust, Ålesund, Norway.
Cancer Epidemiol. 2021 Apr;71(Pt A):101881. doi: 10.1016/j.canep.2020.101881. Epub 2021 Jan 10.
Population-based cancer registries strive to cover all cancer cases diagnosed within the population, but some cases will always be missed and no register is 100 % complete. Many cancer registries use death certificates to identify additional cases not captured through other routine sources, to hopefully add a large proportion of the missed cases. Cases notified through this route, who would not have been captured without death certificate information, are referred to as Death Certificate Initiated (DCI) cases. Inclusion of DCI cases in cancer registries increases completeness and is important for estimating cancer incidence. However, inclusion of DCI cases will generally lead to biased estimates of cancer survival, but the same is often also true if excluding DCI cases. Missed cases are probably not a random sample of all cancer cases, but rather cases with poor prognosis. Further, DCI cases have poorer prognosis than missed cases in general, since they have all died with cancer mentioned on the death certificates.
We performed a simulation study to estimate the impact of including or excluding DCI cases on cancer survival estimates, under different scenarios.
We demonstrated that including DCI cases underestimates survival. The exclusion of DCI cases gives unbiased survival estimates if missed cases are a random sample of all cancer cases, while survival is overestimated if these have poorer prognosis.
In our most extreme scenarios, with 25 % of cases initially missed, the usual practice of including DCI cases underestimated 5-year survival by at most 3 percentage points.
基于人群的癌症登记处努力覆盖人群中诊断出的所有癌症病例，但总会有一些病例被遗漏，没有任何登记处是 100%完整的。许多癌症登记处使用死亡证明来识别其他常规来源未捕获的额外病例，希望能增加大部分遗漏病例。通过此途径通知的病例，如果没有死亡证明信息，将不会被捕获，这些病例被称为死亡证明发起（DCI）病例。将 DCI 病例纳入癌症登记处可提高完整性，对于估计癌症发病率非常重要。然而，通常情况下，如果排除 DCI 病例，也会导致癌症生存估计出现偏差。遗漏的病例可能不是所有癌症病例的随机样本，而是预后较差的病例。此外，DCI 病例的预后通常比遗漏的病例差，因为他们在死亡证明上都提到了患有癌症。
我们进行了一项模拟研究，以估计在不同情况下纳入或排除 DCI 病例对癌症生存估计的影响。
我们证明了纳入 DCI 病例会低估生存率。如果遗漏的病例是所有癌症病例的随机样本，则排除 DCI 病例会给出无偏的生存估计，而如果这些病例的预后较差，则生存估计会被高估。
在我们最极端的情况下，有 25%的病例最初被遗漏，将 DCI 病例纳入通常会使 5 年生存率最多低估 3 个百分点。
