An estimated 37.7% of cancers in the UK are attributable to known risk factors, according to research published in the British Journal of Cancer
The rate is highest in Scotland where the proportion of cancer cases attributable to known risk factors was 41.5% in 2015. Smoking is still the most prominent risk factor for cancer, the research showed.
“Even though smoking prevalence is falling in the population, smoking has a massive impact on the cancer risk of people who do it, therefore it’s still generating a huge number of cancer cases,” said lead author Katrina Brown from the charity Cancer Research UK.
The research team used data on the relative risks of cancer associated with specific risk factors and analysed UK cancer incidence data from 2015 to estimate population attributable fractions (PAFs) for each risk factor.
Overall, nearly four in ten cancer cases were attributable to preventable causes, at 38.6% in men and 36.8% in women. In the UK as a whole, this equated to 135,507 preventable cases of cancer per year.
Tobacco smoking was attributable to 15.1% of cancer cases in the UK in 2015, equating to 54,271 incidences. The second largest attributable cause was obesity or being overweight, at 6.3% of cases or 22,761 cases. Other preventable factors linked to cancer incidence were UV radiation (PAF 3.8%), occupational factors (3.8%), infections (3.6%), alcohol consumption (3.3%) and insufficient fibre intake (3.3%).
There were ten types of cancer where more than 70% of cases were attributable to known risk factors, including melanoma (PAF 86.5%) and lung cancer (78.9%), as well as cervical (99.8%), vaginal (75.0%) and anal cancer (91.3%), mesothelioma (94.4%), nasopharyngeal cancer (85.0%) and laryngeal cancer (72.5%).
Brown and colleagues said this was the first time PAFs have been available for individual UK countries, and this should help better inform regional public health strategies. The proportion of attributable cancers was 37.3% in England, 37.8% in Wales and 38.0% in Northern Ireland, compared with 41.5% in Scotland.
The researchers suggested this between-country difference may be owing to the greater prevalence of tobacco smoking and lung cancer in Scotland compared with the other UK countries. The findings also highlight the need for greater support in reducing cancer risk in deprived communities in the UK, they added.
 Brown K, Rumgay H, Dunlop C et al. The fraction of cancer attributable to modifiable risk factors in England, Wales, Scotland, Northern Ireland, and the United Kingdom in 2015. Br J Cancer 2018. doi: 10.1038/s41416-018-0029-6