Martin Wiseman, Kathryn Allen, and Rachel Thompson: Weighing the evidence on cancer prevention

Scientists gathered at the World Cancer Congress in Montreal, Canada last week to share experience from research and practice, and to consider solutions to reduce the impact of cancer on communities around the world. The theme, “Connecting for Global Impact” highlights the need for continued support and momentum in translating knowledge gained through research and practice to reduce the burden of incident cancer, and also to benefit those living with and affected by cancer.

In 2008 there were 12.7 million cases of cancer worldwide. This is projected to rise to 21.2 million by 2030. Cancer and other non-communicable diseases (NCDs) such as cardiovascular disease, diabetes, and chronic respiratory diseases are a major threat to global health. They account for more than 60% of global deaths with nearly 80% of NCD deaths occurring in low and middle income countries.

At the 65th World Health Assembly member states agreed to a global target of a 25% reduction in premature mortality from NCDs by 2025. Achieving this will require concerted action based on solid evidence.

The public is continually exposed to health related information. Everyday articles appear in the media about foods that supposedly either cause or prevent cancer. This rather piecemeal approach makes it hard to see the bigger picture, and confuses people. According to a 2009 YouGov survey commissioned by the World Cancer Research Fund (WCRF), 52% of people think scientists are always changing their minds about what causes or prevents cancer, and 46% did not trust media reporting on cancer risk. In fact  there is broad consensus among the scientific community about what the major causes of cancer are.

Scientists also have a huge task in keeping up to date. In the last six years alone, twice as many papers from cohort studies and randomised controlled trials exploring the links between food, nutrition, physical activity, and six common cancers (breast, colorectal, prostate, pancreas, endometrium, and ovary) were published compared with the previous 50 years. How then to keep track and make sense of this vast repository of information in order to give context to the rather fragmented way that scientific understanding often emerges?

WCRF International has set up the Continuous Update Project (CUP) to provide the “big picture” for cancer prevention, by creating a literature database—currently the largest in the world—with details from articles on food, nutrition, physical activity and cancer. Systematic reviews of the evidence are conducted and then judged by an independent expert panel of leading scientists and doctors. The CUP strives to use the best methods available and is currently developing innovative approaches to reviewing evidence on cancer survivors and mechanistic data.

The science shows that one third of common cancers can be prevented by food, nutrition, physical activity, and maintaning a healthy weight. With further research we can provide more detailed information for people, but the key challenge to changing behaviour is by making it easier for people to live a healthy lifestyle, through knowledge and environments that are conducive to making healthy choices. This requires a coordinated effort across society, with health professionals and scientists working with government decision makers and policy makers.

If we get this right we will see the benefits not just with cancer. The recommendations for cancer prevention can also help reduce deaths from other NCDs because of the shared risk factors such as overweight and obesity, sedentary lifestyles, and poor diet.

Rather than telling people, “you’ve got cancer,” we could focus more of our energy and resources on stopping cancer before it starts.

Martin Wiseman, Kate Allen and Rachel Thompson, World Cancer Research Fund.

Rachel Thompson is the deputy head of science at World Cancer Research Fund International. She currently manages the Continuous Update Project.

Martin Wiseman is a medical and scientific adviser with World Cancer Research Fund International.

Kathryn Allen is director of science and communications at World Cancer Research Fund International. She is responsible for the scientific and policy  programmes of  World Cancer Research Fund International.