How many people does bowel cancer affect and what is the global survival rate for this condition?
Colorectal cancer is the third most common cancer in men and second in women, with over 1.2 million cases diagnosed worldwide in 2008.
In the UK, after correction for other causes of death, overall 5-year survival for patients diagnosed in 2005-9 is estimated at 55%, worldwide it ranges between 30% and 65%.
How does survival for bowel cancer patients in the UK compare to other countries?
Bowel cancer survival in the UK is over 10% lower at five years than in countries of comparable wealth, with universal access to health care, and longstanding, high-quality, population-based cancer registration.
Has survival for bowel cancer in the UK always been low or is this a recent development?
In the last ten years, bowel cancer survival has improved in the UK, but there is little evidence of a reduction in the survival gap with other high-income countries, because survival has steadily improved over time in other countries too.
How did your research into the low bowel cancer survival in the UK originate?
The persistent deficit in bowel cancer survival in the UK is of concern for all actors along the cancer care pathways, from clinicians to policy-makers and patients. In the past, bowel cancer survival in the UK has been compared with survival in other European countries and in the US. These international studies have helped to shape policy and draw conclusions for action against cancer.
The National Cancer Director, Prof Sir Mike Richards, set up the International Cancer Benchmarking Partnership (ICBP) to find out the origin of the cancer survival deficit in the UK. It is a set of research programmes designed to provide evidence about the best way to improve survival.
ICBP brings together policy-makers, clinicians, epidemiologists, and cancer registry staff from six countries (Australia, Canada, Denmark, Norway, Sweden and the UK) that were chosen for their comparable wealth, universal access to health care and high-quality cancer registration systems.
The extent to which the cancer has spread (stage at diagnosis) is a powerful predictor of survival: survival is much higher for patients diagnosed with “local” disease, where the cancer is still fixed in the organ of origin, than for patients diagnosed with “metastatic” disease, when the cancer has already spread to other organs of the body.
In this study we aimed at quantifying the specific role of stage at diagnosis in explaining low bowel cancer survival in the UK.
How was this research funded?
This research is part of the ICBP, funded by the Department of Health.
What did your research involve?
This research is based on population-based cancer data, looking at the information on stage at diagnosis for over 300,000 cancer patients in six countries, as extracted from their cancer registry record.
This is the first time that stage data have been analysed internationally from these sources in this fashion, i.e. without additional information extracted directly from the medical records, as would be done in high-resolution studies.
Due to its international character, this research involved strong relationships between the Central Analytic Team, based at the London School of Hygiene & Tropical Medicine in London and cancer specialists, pathologists, policy-makers, and scientists in the cancer registries in Australia, Canada, Denmark, Norway, Sweden and the UK.
Cancer registration data for patients diagnosed during 1995-2007 were sent to the UK for centralised quality control and the survival analyses under a common protocol. Stage information was deemed more complete and reliable for patients diagnosed during 2000-7. We reconciled the stage information abstracted from the various systems in use at that time in the participating registries.
We looked at the stage distributions of cancer patients in each country, and estimated bowel cancer survival for patients diagnosed at each stage of disease in each country.
What did your research find to be the reasons behind the low survival for bowel cancer patients in the UK compared to other countries?
Our hypotheses were that international variations in overall bowel cancer survival (survival for all adult patients combined) could be explained either by differences in the distributions of stage at diagnosis between countries or by international differences in survival at each stage of disease.
In the UK, the stage distribution of cancer patients seems favourable, i.e. patients do not seem to be diagnosed at a later stage than their counterparts in Australia, Canada or Sweden, where overall survival is higher. Additionally, survival for UK patients with “regional” disease (involvement of lymph nodes) and “distant” disease (presence of metastases) was lower than that in other countries.
The stage at diagnosis of patients is defined after careful pathological and clinical investigation of the tumour. Such investigations for bowel cancer can include assessments of lymph nodes and a liver biopsy. Treatment is then offered to patients on the basis of their stage of disease.
Improvement in survival has been attributed to rising resection rates, falling post-operative mortality and the increased use of adjuvant chemotherapy. The stage distribution of cancer patients in the UK (high proportions of patients with regional diseases and low proportions of patients with distant diseases) and their low stage-specific survival could reflect sub-optimal investigation as well as a potential deficit in treatments offered to the patients at each stage of disease.
Why do you think the UK had the lowest proportion of colon cancer patients diagnosed at stage A (the earliest stage)?
The proportion of colon cancer patients diagnosed at stage A in the UK was about half that observed in Canada (8.4% vs. 17.3%). For rectal cancer, the proportion of patients diagnosed at stage A is similar to that of other countries.
For both cancers, their survival is similar to that of other countries. Stage A patients present with a tumour that does not invade outside the muscle layers of the intestine. It is probable that the diagnosis of such patients in the UK is delayed.
Do you think the results of this research will help the UK improve the survival of bowel cancer patients?
Low bowel cancer survival in the UK was already known. The specific aim of the study was to understand the role of stage at diagnosis in explaining low cancer survival.
UK patients will benefit from the findings of this research if they are encouraged to seek help earlier in order to be diagnosed at the earliest possible stage; if investigation of stage at diagnosis is more systematic, and if patients then obtain the best possible treatment for the stage of disease that they are diagnosed at.
What further work needs to be done to improve bowel cancer survival?
Further work needs to be done in understanding the treatment offered to UK patients at each stage of disease. Treatment guidelines are similar in the UK and other high-survival countries such as Canada. Research is needed on whether the guidelines are actually being followed.
Work is also required on improving the quality and completeness of the stage information collected in cancer registries so that robust international comparisons of cancer survival by stage can be produced.
Where can readers find more information?
More information on the International Cancer Benchmarking Partnership can be found at http://www.cancerresearchuk.org/cancer-info/spotcancerearly/ICBP/
The CONCORD programme, global surveillance of cancer survival: https://www.lshtm.ac.uk/
EUROCARE, survival of cancer patients in Europe: http://www.eurocare.it/
About Camille Maringe
Camille Maringe is a research fellow in the CRUK Cancer Survival Group at the London School of Hygiene & Tropical Medicine. Her main research interests are the study of prognostic factors in cancer survival.
She trained as a statistician in the Université Paris IX, Dauphine in Paris, France and at ENSAI in Rennes, France.
She is involved in a variety of projects including cancer survival in South Asian migrants to England, and the first module of the International Cancer Benchmarking Partnership.
She is involved in the Department of Health Policy Research Unit on cancer awareness, screening and early diagnosis. She is pursuing a part-time PhD looking at methods of prediction and projection of cancer survival.
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