Estimates of lung and pancreatic cancer survival in Sweden with and without inclusion of death certificate initiated (DCI) cases

Abstract

Introduction International differences in cancer incidence and survival may partly reflect differences in cancer registration practices. As opposed to most other National Cancer Registries, Death Certificate Initiated (DCI) cases are not included in the Swedish Cancer Register. We characterized cases not reported to the Swedish Cancer Register and assessed the impact of inclusion of DCI cases on the completeness and estimates of one-year lung and pancreatic cancer survival. Methods We used information in the Swedish Cause of Death Register to identify individuals in two Health Care Regions (West and Uppsala Örebro) with lung or pancreatic cancer as cause of death in 2013. These records were cross-linked to the Cancer Register to identify individuals without a corresponding cancer registration, i.e. Death Certificate Notified (DCN) cases. DCN cases were cross-linked to the Patient Register to retrieve hospital discharge information to confirm the diagnosis. In a separate step, trace-back of DCN cases was performed to access medical records to validate the diagnosis. Results Following validity checks, an estimated 16% and 34% of individuals with a diagnosis of lung or pancreatic cancer, respectively, had not been reported to the SCR. Non-reported patients were older and had a considerable poorer survival than those included in the SCR. Inclusion of DCI cases decreased one-year lung cancer overall survival from 45% to 41%. The corresponding decrease for pancreatic cancer was five percentage points, from 29% to 24%. Conclusions Lung and pancreatic cancers are underreported to the SCR yielding too low incidence rates and upward biased survival estimates. We conclude that implementation of systematic death certificate processing with trace-back is feasible also within the Swedish system with regionalized cancer reporting. Verifying registrability by use of information in the Patient Register provided a good approximation of “corrected” survival estimates based on chart review.