Elsevier

Cancer Epidemiology

Volume 75, December 2021, 102023
Cancer Epidemiology

The validity of cancer information on death certificates in Norway and the impact of death certificate initiated cases on cancer incidence and survival

https://doi.org/10.1016/j.canep.2021.102023Get rights and content
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open access

Highlights

  • A large proportion of death certificate notifications not a new cancer case.

  • Death certificate initiated cases increase incidence but bias survival downwards.

  • Excluding death certificate initiated cases will bias survival upwards.

  • Only minor survival bias in the Cancer Registry of Norway.

Abstract

Background

Death certificates are an important source of information for cancer registries. The aim of this study was to validate the cancer information on death certificates, and to investigate the effect of including death certificate initiated (DCI) cases in the Cancer Registry of Norway when estimating cancer incidence and survival.

Methods

All deaths in Norway in the period 2011–2015 with cancer mentioned on the death certificates were linked to the cancer registry. Notifications not registered from other sources were labelled death certificate notifications (DCNs), and considered as either cancer or not, based on available information in the registry or from trace-back to another source.

Results

From the total of 65 091 cancers mentioned on death certificates in the period 2011–2015, 58,425 (89.8%) were already in the registry. Of the remaining 6 666 notifications, 2 636 (2 129 with cancer as underlying cause) were not regarded to be new cancers, which constitutes 4.0% of all cancers mentioned on death certificates and 39.5% of the DCNs. Inclusion of the DCI cases increased the incidence of all cancers combined by 2.6%, with largest differences for cancers with poorer prognosis and for older age groups. Without validation, including the 2 129 disregarded death certificates would over-estimate the incidence by 1.3%. Including DCI cases decreased the five-year relative survival estimate for all cancer sites combined with 0.5% points.

Conclusion

In this study, almost 40% of the DCNs were regarded not to be a new cancer case, indicating unreliability of death certificate information for cancers that are not already registered from other sources. The majority of the DCNs where, however, registered as new cases that would have been missed without death certificates. Both including and excluding the DCI cases will potentially bias the survival estimates, but in different directions. This biases were shown to be small in the Cancer Registry of Norway.

Keywords

Cancer registration
Data quality
Death-certificate-initiated case
Record linkage
Cancer survival

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