Participation in routine colorectal cancer screening is associated with a 43 per cent lower risk of dying from the disease, according to new estimates from Swedish researchers. While universal testing programs are offered, about a third of eligible adults still fail to submit home test samples.
Colorectal cancer is one of the most common forms of cancer, with a favourable prognosis if detected early. Universal screening has been introduced throughout Sweden, meaning testing is offered to people aged 60–74 every two years. Participants are sent a screening kit to their home address and asked to provide a stool sample, which is analysed for small amounts of blood that are not visible to the naked eye. If blood is detected, further investigation is offered, usually in the form of a colonoscopy.
Stockholm-Gotland Screening Data Reveals Survival Gains
Stockholm and Gotland were early adopters, introducing routine screening as early as 2008. Researchers at Karolinska Institutet and Umeå University have now followed these individuals for up to 14 years to investigate the impact of screening on mortality rates. Under the universal screening framework implemented across Sweden, adults aged 60 to 74 receive a testing kit at their home address every two years.
The study included 376,511 people, and during the follow-up period, 1,668 deaths from colorectal cancer were recorded. By comparing those who were invited to screening between 2008 and 2012 with a control group who were either invited later or not at all, the researchers used a statistical method to account for factors that could distort the results, such as some people in the control group being given the opportunity to participate later on, and some invited individuals not participating. When these factors were taken into account, an invitation to screening was associated with a 26 per cent lower risk of dying from colorectal cancer, while active participation was associated with a 43 per cent lower risk.
A previous evaluation of the programme showed that those who received an invitation to screening had a 14 per cent lower risk of dying from the disease,
says Johannes Blom, senior consultant and associate professor at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, and the study’s corresponding author.
That initial figure has now been compared with more granular long-term tracking. The updated analysis published in JAMA Network Open demonstrates that actual participation yields a lower mortality than a mere invitation.
“We have now been able to show that the mortality is significantly lower than that among those who actually take part in the screening.”
Johannes Blom, senior consultant and associate professor at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet
Dietary Patterns, Health Services, and Residual Compliance Gaps
Parallel research examining lifestyle factors and cancer risk sheds additional light on how health habits intersect with health outcomes. Researchers from Oxford Population Health’s Cancer Epidemiology Unit (CEU) analysed data from over 472,000 participants in the UK Biobank to investigate the association between diet and cancer risk. The results have been published in BMC Medicine. British participants (aged between 40-69 years) were recruited to the UK Biobank Study between 2006 and 2010, and completed questionnaires about how often they ate meat and fish. In men, compared with regular meat-eaters, the risk of colorectal cancer was lower in low meat-eaters (11% less), fish-eaters (31% less), and vegetarians (43%).
Lead author for the study Cody Watling, a DPhil student within CEU, said: ‘Our study found that being a low meat-eater, fish-eater, or vegetarian was associated with a significantly lower risk of all cancer. But it is not yet clear whether these differences are due to dietary factors or non-dietary effects, as differences in use of health services, including cancer screening, may also have influenced our findings.’
Even when tests are made freely available and require minimal effort, public compliance remains an obstacle. It is noted that around a third of people do not submit a sample, leaving a substantial portion of the target demographic not participating in the screening.
Although screening is offered free of charge and the test is simple to carry out, around a third of people do not submit a sample,
says Johannes Blom, senior consultant and associate professor at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet.
The study was funded by the Swedish Cancer Society, the Swedish Research Council and Region Stockholm. The researchers state that they have no conflicts of interest. Some of the study’s strengths include the large study population, the long follow-up period and the use of Swedish health registers. However, the researchers emphasise that the results are based on statistical adjustments for various types of bias, meaning that some uncertainties remain.
“Our study highlights the importance of taking part in colorectal cancer screening, and shows that it can actually save lives.”
Johannes Blom, senior consultant and associate professor at the Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet
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