Incomplete diagnostic investigation and failure to get the best treatment are the most likely reasons why survival for bowel cancer patients is lower in the UK than in other comparable countries, according to new research published in the journal Acta Oncologica.
The research, led by the London School of Hygiene & Tropical Medicine, was carried out in Australia, Canada, Denmark, Norway, Sweden and the UK for the International Cancer Benchmarking Partnership (ICBP). The study included more than 310,000 bowel cancer patients diagnosed during 2000-07.
Bowel cancer is sometimes called colorectal cancer, which includes cancers of the colon and rectum. This study examined both types of bowel cancer.
The researchers examined how far the patients' cancer had spread at the time of diagnosis – from very early (localised, stage A) to very late (spread to other parts of the body, stage D). They also examined the proportion of patients at each stage of disease who survived for one year and three years after diagnosis, after correction for the impact of other causes of death.
Two-thirds (67%) of colon cancer patients in the UK survived for at least one year, compared with 80% in Sweden. Three-quarters (75%) of rectal cancer patients in the UK survived for one year or more, compared with 84% in Sweden.
Low overall survival in a particular country can arise either because the patients there tend to be diagnosed at a later stage of disease than in other countries, or because survival at each stage of disease is lower than in other countries.
The proportion of colon cancer patients diagnosed at the earliest stage (stage A) was lowest in the UK - only 8% compared with 11-17% elsewhere. But UK patients were also less likely to be diagnosed at the most advanced stage (20% at stage D, compared with 24-31% elsewhere).
For both colon and rectal cancer, survival among UK patients diagnosed at the earliest stage of disease (stage A) was similar to that in the other five countries (96%, compared to 92-98% elsewhere), but survival in the UK was consistently lower for those diagnosed at a more advanced stage (5-11% lower than elsewhere).
The researchers used population-based data for all patients diagnosed in a given country or region, not just the small proportion of patients included in clinical trials. The international differences in survival may arise from differences in the availability or use of diagnostic tests, and in the use of surgery, chemotherapy or radiotherapy at each stage of diagnosis. Countries do not all collect information on stage at diagnosis in the same way, however, and this can cause artefacts in international survival comparisons.
Camille Maringe, lead author based at the Cancer Research UK Cancer Survival Group at the London School of Hygiene & Tropical Medicine, said: "Accurate investigation of how far the cancer has spread (the stage) when it is diagnosed is essential for clinicians to be able to offer their patients the most appropriate treatment. This will increase survival. Investigation does not appear to be as thorough in the UK as in other countries, and except for patients with local tumours, survival is lower than in other countries at each stage of disease.
"We observed international differences in survival at each stage of disease. These differences are wider for older patients, and for patients whose disease is very advanced when they are diagnosed.
"Improvements are urgently needed in the quality and thoroughness of the medical tests that are used to assess the stage at diagnosis for each patient. The data collected by cancer registries on stage at diagnosis also need to be more accurate and complete. This will enable more accurate international comparisons of survival at each stage of disease. In turn, it will enable patients, doctors and healthcare planners to see which countries are setting the best standards, and what improvements are required to reach the highest levels of survival."
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Maringe et al. Stage at diagnosis and colorectal cancer survival in six high-income countries: A population-based study of patients diagnosed during 2000 – 2007 Acta Oncologica, 2013. DOI: 10.3109/0284186X.2013.764008