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

Woods LM, Coleman MP, Lawrence G, Rashbass J, Berrino F, Rachet B - BMJ (2011)

Bottom Line: Mean absolute percentage change in one year and five year relative survival associated with each simulated error.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.

View Article: PubMed Central - PubMed

Affiliation: Cancer Research UK Cancer Survival Group, Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK. laura.woods@lshtm.ac.uk

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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Related in: MedlinePlus

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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fig1: 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

Mentions: Simulating errors in the date of diagnosis changed the estimates of survival, but the observed difference in survival between England and Sweden could be explained only if very large proportions of patients were affected by large errors (fig 1). For example, for women diagnosed with breast cancer in 1995-9, the survival time of 70% of women known to be dead would have to have been incorrectly recorded by an average of at least one year to increase one year survival after breast cancer by 4%, whereas the difference in one year survival between Sweden and England reported in EUROCARE-4 was 4.7% (table 1).17 Similarly, to explain the 7.3% difference in five year survival between Sweden and England, 30% of women known to be dead would have to have had their survival time incorrectly shortened by an average of at least five years (fig 2). For women diagnosed with breast cancer in 2005-7, the difference in five year relative survival between Sweden and England is predicted to be 6.9% (table 1).5 Again, this difference could only be fully explained if the survival time of 30% of women known to be dead had been incorrectly shortened by an average of five years (data not shown).


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

Woods LM, Coleman MP, Lawrence G, Rashbass J, Berrino F, Rachet B - BMJ (2011)

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
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3111483&req=5

fig1: 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
Mentions: Simulating errors in the date of diagnosis changed the estimates of survival, but the observed difference in survival between England and Sweden could be explained only if very large proportions of patients were affected by large errors (fig 1). For example, for women diagnosed with breast cancer in 1995-9, the survival time of 70% of women known to be dead would have to have been incorrectly recorded by an average of at least one year to increase one year survival after breast cancer by 4%, whereas the difference in one year survival between Sweden and England reported in EUROCARE-4 was 4.7% (table 1).17 Similarly, to explain the 7.3% difference in five year survival between Sweden and England, 30% of women known to be dead would have to have had their survival time incorrectly shortened by an average of at least five years (fig 2). For women diagnosed with breast cancer in 2005-7, the difference in five year relative survival between Sweden and England is predicted to be 6.9% (table 1).5 Again, this difference could only be fully explained if the survival time of 30% of women known to be dead had been incorrectly shortened by an average of five years (data not shown).

Bottom Line: Mean absolute percentage change in one year and five year relative survival associated with each simulated error.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.

View Article: PubMed Central - PubMed

Affiliation: Cancer Research UK Cancer Survival Group, Department of Non-Communicable Disease Epidemiology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK. laura.woods@lshtm.ac.uk

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.

Show MeSH
Related in: MedlinePlus