Cancer survival improves in UK but still lags behind other high income countries
BMJ 2019; 366 doi: https://doi.org/10.1136/bmj.l5508 (Published 11 September 2019) Cite this as: BMJ 2019;366:l5508
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I recommend that Dr Herron looks at the Methods section of the ICBP SURVMARK-2 paper [1]:
“In this longitudinal, population-based study, we obtained patient-level data on primary cancers of the oesophagus, stomach, colon, rectum, liver, pancreas, lung, and ovary from 21 population-based cancer registries covering 21 jurisdictions in seven countries: Australia (New South Wales, Victoria, and Western Australia), Canada (Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Quebec, and Saskatchewan), Denmark, Ireland, New Zealand, Norway, and the UK (England, Scotland, Wales, and Northern Ireland).”
The number of cases of each cancer should be related to the population covered by each registry, not the national population of each country. It so happens that the UK achieves virtually complete coverage by its cancer registries, another triumph of the NHS. Notwithstanding the fact that there are more registered cases in the UK, there are sufficient cases recorded by the other registries and their data quality is also sufficient to permit survival estimates with narrow enough confidence intervals to be sure that the UK shortfall in outcomes is real.
1] Arnold M, Rutherford M, Bardot A, et al. Progress in cancer control: survival, mortality and incidence in seven high-income countries 1995-2014 (ICBP SURVMARK-2): a population based study. Lancet Oncol2019. doi:10.1016/S1470-2045(19)30456-5.
Competing interests: No competing interests
Dr Crawford (1) draws attention to the need to grow NHS services and also comments on the quality of data comparing cancer survival rates internationally.
The population of the UK is currently 1.8 times that of Canada. In the lancet study (2), the number of cases of oesophageal cancer in the UK was 6.6 times bigger than the number in Canada. The number of cases of stomach cancer was 3.9 times bigger. The number of cases of colon cancer was 2.6 times bigger. The number of cases of rectal cancer was 3.2 times bigger. The number of cases of pancreatic cancer was 2.9 times bigger. The number of cases of lung cancer was 2.7 times bigger. The number of cases of ovarian cancer was 3.3 times bigger.
The UK has a population 2.7 times larger than that of Australia. In the Lancet study the number of cases of oesophageal cancer in the UK was 10.2 times bigger than the number in Australia. The number of cases of stomach cancer was 6.5 times bigger. The number of cases of colon cancer was 4.3 times bigger. The number of cases of rectal cancer was 4.6 times bigger. The number of cases of pancreatic cancer was 5.3 times bigger. The number of cases of lung cancer was 6.9 times bigger. The number of cases of ovarian cancer was 7.2 times bigger.
This pattern continues across different cancers and across different countries. The rate of population growth in these countries is similar across the period of data collection. It seems unlikely that the underlying cancer prevalence is so much higher in the UK than the prevalence in the other high income countries, therefore we should consider whether the cancer registers studied have different rates of success in capturing cases. If this is so, it seems likely that it will affect the international comparisons in some way. That the NHS needs more investment is clear; whether these comparisons help to guide where that funding should be focused, less so.
(1) Crawford S. Response to critic: Cancer survival improves in UK but still lags behind other high income countries
(2) Arnold M, Rutherford M, Bardot A, et al. Progress in cancer control: survival, mortality and incidence in seven high-income countries 1995-2014 (ICBP SURVMARK-2): a population based study. Lancet Oncol2019. doi:10.1016/S1470-2045(19)30456-5.
Competing interests: No competing interests
Response to critic: Cancer survival improves in UK but still lags behind other high income countries
Dr Herron[1] cites Prof Bob Souhami's 2010 critique of the work around that time that was looking to promote earlier diagnosis of cancer in which he comments on the EUROCARE4 European comparison of national data, itself published in 2007-9[2].
Since then there has been another iteration of the EUROCARE process which tells the same story and the Lancet Oncology paper reported by the BMJ adds to it by looking at comparator countries outside Europe[3,4]. The questions of data reliability have been carefully assessed over the past decade and the robustness of the studies has been confirmed.
Furthermore, the consistent place of the four countries that form the UK, the Republic of Ireland and Denmark at the bottom of the league table suggests that they have something in common and they do indeed share the characteristic of primary care gatekeeping for non-emergency access to diagnostic pathways. We can take enormous pride in the fact that there is no paywall barrier for the UK citizen who needs medical care but we must not have a starry-eyed attitude that the NHS can do no wrong; it is too small to achieve all it ought to. How gatekeeping access to cancer diagnostics for the purpose of protecting overstretched services works to the detriment of members of the public who have cancer has been discussed recently in the BMJ [5].
1] Herron D. Cancer survival improves in UK but still lags behind other high income countries bmj.l5508/rapid-responses
2] Souhami R. Are UK cancer cure rates worse than in most other European countries? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2814259/
3]Baili P, Di Salvo F, Marcos-Gragera R et al.; EUROCARE-5 Working Group. Age and case mix-standardised survival for all cancer patients in Europe 1999–2007: results of EUROCARE-5, a population-based study. Eur J Cancer 2015; 51: 2120–9
4]Arnold M, Rutherford M, Bardot A, et al. Progress in cancer control: survival, mortality and incidence in seven high-income countries 1995-2014 (ICBP SURVMARK-2): a population based study. Lancet Oncol2019. doi:10.1016/S1470-2045(19)30456-5.
5] Oliver D. Don’t blame GPs for late cancer diagnoses BMJ 2019;366:l4625 plus Rapid Responses
Competing interests: No competing interests
The reporting emphasis here (unlike in the original paper) is on differences between survival rates in the UK and elsewhere, but there is an inherent likelihood of bias when survival rates are compared by observational data derived from general populations. In addition, the UK has been shown to be more competent than some other countries at coding and registering cancers at the time of diagnosis. (1)
It would make more sense to present survival rates alongside incidence and mortality rates, as the reader could then easily draw their own conclusions on whether comparisons such as those made in the headline are faulty. The original paper states that "truly valid comparisons require differences in registration practice, classification, and coding to be minimal."
(1) Are UK cancer cure rates worse than in most other European countries? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2814259/
Competing interests: No competing interests
Re: Cancer survival improves in UK but still lags behind other high income countries
Taking the example of Canada, the cancer registries listed in the study (1) are those of Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Quebec, and Saskatchewan. These are in fact all the provinces in Canada. Canada also has three territories: which together have a population of 116,359 -- that is, 0.3% of the total population of Canada. If the study therefore included cancer registries which endeavoured to capture all cancers occurring across that vast majority of that country’s population, it is not unreasonable to ask how and why they missed some of cancers that obviously did occur, and how that affects the data when it is compared to other registries which performed better in that respect.
On quality control, the paper states “We subjected each registry dataset to several data quality assessments, which included scrutinising data for specific anomalies, such as instances of negative survival duration (date of death occurring before date of diagnosis); out-of range dates of diagnosis or dates of death, or both; and invalid vital status codes. Additionally, every case was checked for consistency in terms of patient sex and sex specific cancer site; site and morphology; age and site; age and morphology; and age, site, and morphology.” These quality controls will aim to ensure that variation in incidence and survival within individual registries across time represent real changes, but they do not address the issue of cancer diagnoses not entering into the register in the first place. The discussion in the paper focuses on the improvements noted in most territories. When it comes to international comparisons, the discussion states that “specific aspects of registration that might influence survival are uncollectable or beyond the control of the registry, such as the completeness of registration, characteristics of patients with cancer who are not included in the registries, and complete ascertainment of deaths. The individual and cumulative effect of these factors is extremely difficult, if not impossible, to measure.”
1) Arnold M, Rutherford M, Bardot A, et al. Progress in cancer control: survival, mortality and incidence in seven high-income countries 1995-2014 (ICBP SURVMARK-2): a population based study. Lancet Oncol2019. doi:10.1016/S1470-2045(19)30456-5.
Competing interests: No competing interests