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. 2011 Jun 9:342:d3399.
doi: 10.1136/bmj.d3399.

Evidence against the proposition that "UK cancer survival statistics are misleading": simulation study with National Cancer Registry data

Laura M Woods  1 , Michel P Coleman, Gill Lawrence, Jem Rashbass, Franco Berrino, Bernard Rachet
Affiliations

Evidence against the proposition that "UK cancer survival statistics are misleading": simulation study with National Cancer Registry data

Laura M Woods et al. BMJ. .

Abstract

Objectives: To simulate each of two hypothesised errors in the National Cancer Registry (recording of the date of recurrence of cancer, instead of the date of diagnosis, for registrations initiated from a death certificate; long term survivors who are never notified to the registry), to estimate their possible effect on relative survival, and to establish whether lower survival in the UK might be due to one or both of these errors.

Design: Simulation study.

Setting: National Cancer Registry of England and Wales. Population Patients diagnosed as having breast (women), lung, or colorectal cancer during 1995-2007 in England and Wales, with follow-up to 31 December 2007.

Main outcome measure: Mean absolute percentage change in one year and five year relative survival associated with each simulated error.

Results: To explain the differences in one year survival after breast cancer between England and Sweden, under the first hypothesis, date of diagnosis would have to have been incorrectly recorded by an average of more than a year for more than 70% of women known to be dead. Alternatively, under the second hypothesis, failure to register even 40% of long term survivors would explain less than half the difference in one year survival. Results were similar for lung and colorectal cancers.

Conclusions: Even implausibly extreme levels of the hypothesised errors in the cancer registry data could not explain the international differences in survival observed between the UK and other European countries.

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Conflict of interest statement

Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

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Fig 1 Simulated increase in one year relative survival in England and Wales by percentage of deceased patients whose survival time was extended, and mean extension of their survival: women with breast cancer diagnosed 1995-9. Baseline estimate is relative survival estimate in observed data before any simulated changes in survival time. Data points represent absolute percentage change in relative survival from baseline estimate (zero). Absolute difference in relative survival observed between age standardised survival in England and Sweden in EUROCARE-4 (table 1) is represented by horizontal line above baseline
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Fig 2 Simulated increase in five year relative survival in England and Wales by percentage of deceased patients whose survival time was extended, and mean extension of their survival: women with breast cancer diagnosed 1995-9. Baseline estimate is relative survival estimate in observed data before any simulated changes in survival time. Data points represent absolute percentage change in relative survival from baseline estimate (zero). Absolute difference in relative survival observed between age standardised survival in England and Sweden in EUROCARE-4 (table 1) is represented by horizontal line above baseline
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Fig 3 Age specific incidence rates for breast cancer (women) in England and Sweden, with incidence by age that would be observed in England if 20%, 30%, or 40% of putatively unregistered long term survivors were added to data, with “extreme” age skew (see text)
See this image and copyright information in PMC

References

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