How does Cancer Research UK evaluate research on the causes of cancer?

Cancer Research UK is an independent charity. We exist to beat cancer.

At Cancer Research UK, we play a vital role in providing accurate health information on the causes of cancer. This helps people take steps to reduce their risk. Our advice for the public is based on lots of good-quality evidence built up over many years.

On this page we aim to explain how we evaluate research on the causes of cancer. Evaluating research means we check the quality of it and assess what it can tell us about cancer risk. 

How can research prove what causes cancer?

It’s fair to question how we know that something causes cancer.  

It’s not possible to know what caused an individual person’s cancer. But thanks to research we know more than ever before about the things that can cause or prevent cancer in the general population.

For research to prove something is a cause of cancer there must be:

• good-quality studies of humans that show a cancer-causing (carcinogenic) effect. 
• evidence that reflects real-world situations. This means investigating exposure to a risk factor in ways that are accurate to how people encounter it in real life.
• explanation(s) for how the risk factor causes cancer. In research this is called a mechanism. An example is by damaging our DNA.

Let's look at smoking as an example:

Evidence for tobacco causing cancer dates back to the 1950s. So there are many decades of good-quality studies showing the link. Many studies are long-term studies following people who smoke, comparing their risk of cancer to people who don’t smoke. The research shows that a person’s risk of cancer increases the more they smoke and the longer they smoke for.

We also know of many ways that smoking causes cancer. The main way is that chemicals in tobacco smoke directly damage our DNA. All this evidence is strong-enough proof that smoking is a cause of cancer.

Further down we explore what good research looks like.

How does Cancer Research UK review evidence on the causes of cancer?

We have a team who are experts in studying how diseases happen and spread (epidemiology). Our experts regularly review new research on the causes of cancer to make sure our information is up to date.

We develop our health information by looking at lots of good-quality research carried out over many years. New research comes out all the time which we review, but it is unlikely that one individual study or paper would change our position on a topic.

As part of our evaluations of the evidence base we also consider conclusions made by other expert health organisations.

For example:

• International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO)
• World Cancer Research Fund (WCRF)

Our health advice to the public is based on our own review and interpretation of the available evidence. We consider the best way to explain the evidence to the public alongside advice that is empowering and actionable.

We also play a part in stopping misinformation about cancer. For some topics we may conclude that something is not a risk factor for cancer. This doesn’t mean that studies showing an increased risk don’t exist. But they may not be good-quality, and overall the evidence isn’t strong-enough.

What does good-quality research look like?

We need good-quality research to be able to draw conclusions on what affects cancer risk. Some studies are better quality than others based on their design (the way the study is done).

We assess how well a study has been carried out and what the results can, and cannot, tell us about our risk of cancer.

Here are some important things we look at when evaluating if a study provides good evidence:

1) Study type

Studies in animals or cells can help researchers understand how cancer happens. But they aren’t always good evidence for how a risk factor affects people. To prove something is a risk factor, good-quality studies of people in the real world are needed. Good studies can also combine and analyse the results of many other studies. These give a bigger, clearer picture of the overall evidence.

2) Study size and length

The size of a study can affect how reliable the results are. In small studies of fewer people the results are more likely to be caused by chance rather than showing us a true effect or pattern. Studies that only follow people for a short amount of time are less reliable as they can miss any long-term effects. A good study follows thousands of people over many years.

3) Taking into account known cancer risk factors

There are lots of things that can affect a person’s risk of cancer (risk factors). In a good study all known cancer risk factors are considered in the study design and results analysis. If this is not done, other risk factors may impact the results and the results may not be valid.

For example a study looking at air pollution and lung cancer risk should also take into account whether participants smoke or not. This is because smoking is the biggest cause of lung cancer. If adjustments for smoking are not made in the study design the effect of air pollution on lung cancer risk would likely be overestimated. (The damage caused by smoking will have influenced the results).

4) Peer-review and funding

Good-quality studies are often published in a peer-reviewed scientific journal. This means that other experts (peers) have assessed the study design and results. We also look at who funded a study, as this can bias how the results and conclusions are presented. For example, Cancer Research UK disregards all research funded by the tobacco industry.

Cancer Research UK is a trusted health information creator

We are awarded with the Patient Information Forum (PIF) TICK as a quality mark for trusted health information. The PIF TICK recognises that we have a robust process for producing health information, and it has met yearly assessment criteria.

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Overall the PIF TICK shows that our health information is:

• Evidence-based, accurate and up to date
• Easy to understand and use
• Written by trained members of staff

It’s important to get your information on cancer from a trusted source. When you see the PIF TICK it’s a sign of health information you can trust.

Find out more about the PIF TICK (external site).

You’ll find detailed information about how we research and write our health information in our Editorial Policy.