Cancer Risk Factors Revision Notes | GCSE AQA Higher Biology

1. What Makes Cancer More Likely?

Cancer isn't random. Scientists have spent decades tracking patterns, asking: why do some people get cancer while others don't? The answer lies in risk factors — things that make cancer more likely to develop.

Think of risk factors like loading dice. Normal cells have built-in protection against becoming cancerous. But each risk factor tips the odds slightly against you. The more risk factors you have, the more loaded the dice become.

Trap: Many students think risk factors guarantee you'll get cancer. They don't. They just increase probability. Someone with multiple risk factors might never develop cancer, while someone with none might still get it.

2. Lifestyle Risk Factors - The Choices We Make

Lifestyle risk factors are the ones you can control. Scientists have identified several key behaviours that significantly increase cancer risk across different types.

Smoking is the biggest single risk factor. It doesn't just cause lung cancer — it increases risk for at least 14 different cancer types. The chemicals in tobacco smoke are carcinogens that directly damage DNA.

Alcohol consumption increases risk for liver, breast, bowel, and throat cancers. Your liver breaks down alcohol into acetaldehyde, which damages DNA and prevents cells from repairing themselves properly.

Diet and obesity affect cancer risk through multiple pathways. Processed meats contain chemicals that can damage the bowel lining. Excess body fat produces hormones and inflammatory substances that promote cancer growth.

UV radiation exposure from sun or sunbeds damages skin cell DNA directly, leading to melanoma and other skin cancers. The damage accumulates over time — childhood sunburn increases adult cancer risk.

This is where students often get confused about cause and effect. Let's check your understanding:

3. Genetic Risk Factors - What We Inherit

Some people inherit genetic changes that make them more susceptible to cancer. These aren't lifestyle choices — they're written into your DNA from birth.

The most famous examples are the BRCA1 and BRCA2 gene mutations. Women who inherit these faulty genes have up to an 80% lifetime risk of breast cancer, compared to about 12% for the general population.

Other genetic risk factors include mutations linked to bowel cancer (familial adenomatous polyposis), skin cancer (xeroderma pigmentosum), and various rare cancer syndromes.

Key point: Having a genetic risk factor doesn't mean you'll definitely get cancer. It means your cells are more vulnerable to damage from other factors. This is why genetic counselling often focuses on lifestyle modifications to reduce overall risk.

4. How Risk Factors Work Together

Risk factors don't work in isolation — they interact. Someone with genetic susceptibility who also smokes faces much higher risk than either factor alone would suggest.

This explains why cancer rates vary so dramatically between populations. Japanese women have lower breast cancer rates than Western women, partly due to different diets and lifestyle factors. But when Japanese women move to Western countries and adopt Western lifestyles, their cancer rates increase.

The interaction works both ways. Protective factors can reduce risk even in genetically susceptible people. Regular exercise, healthy diet, and avoiding carcinogens can significantly lower cancer probability.

5. Evidence and Cancer Types

Different cancers have different risk factor profiles. Scientists have built this knowledge through decades of epidemiological studies — tracking large populations over time to identify patterns.

Lung cancer: 85% linked to smoking. Other factors include radon gas, asbestos exposure, and air pollution.

Skin cancer: Primarily UV radiation exposure. Fair skin (genetic factor) increases susceptibility.

Breast cancer: Complex mix of genetic factors (BRCA mutations), hormonal factors (age at menopause), and lifestyle factors (alcohol, obesity).

Bowel cancer: Strong links to processed meat consumption, low fibre diet, and inherited genetic syndromes.

6. Exam Technique - Risk Factor Questions

Exam questions on cancer risk factors often test your ability to interpret data and evaluate evidence. Here's how to approach them systematically.

Worked example: Worked Example: Applying Cancer Risk Factors

Use this method to answer an exam-style question about what makes cancer more likely?.

1. Underline the key term in the question and write a one-line definition linked to cancer risk factors. — This prevents vague answers and anchors the response in required terminology.
2. Describe the process in logical order using scientific vocabulary and direction words (increase/decrease, faster/slower). — Examiners award marks for clear causal chains, not isolated facts.
3. If data is provided, show each step of working and include units. — Method marks depend on visible working, even if the final answer is not fully correct.
4. Finish with a sentence explaining what the result shows about cancer risk factors. — Interpretation secures higher-band marks.

Answer: A complete response links mechanism, evidence, and conclusion for cancer risk factors.

Command word focus: 'Explain' questions want you to link the risk factor to the biological mechanism. For example: 'UV radiation damages DNA in skin cells, which can lead to uncontrolled cell division and skin cancer.'

Common mistakes to avoid: Don't confuse correlation with causation. Just because two things happen together doesn't mean one causes the other. Always consider alternative explanations for patterns in data.