To describe a data artefact in degree‐of‐spread at first presentation in the New South Wales Central Cancer Registry (NSW CCR), the only Australian cancer registry that records degree‐of‐spread data for all solid tumours.
Method
Trends in the proportions of cancer cases diagnosed annually over 1972‐2004 by degree‐of‐spread categories of localised, regional, distant and unknown were calculated for each major cancer type.
Results
Excepting breast cancer and melanoma, the proportion of localised cancer cases reported from 1993‐1998 was approximately 5% lower than expected, and was mirrored by an artefactual increase in unknown degree‐of‐spread cases.
Conclusion
This artefact was caused by the introduction of the Electronic Notification System and cannot easily be remedied retrospectively. However, regional and distant categories of degree‐of‐spread in the NSW CCR data are reliably recorded for the 1972‐2004 period.
Implications
It is important that past and present cancer data users are notified and understand the quality issues with NSW CCR degree‐of‐spread data, and use it as recommended to avoid anomalous results or conclusions.
