Cancer: Scientists have identified lifestyle risk factors for various types of cancer. There are also genetic risk factors for some cancers.

The idea

Cancer begins when changes in DNA cause cells to divide uncontrollably, forming a tumour. Scientists have identified lifestyle risk factors that increase the chance of these changes, such as smoking tobacco, drinking alcohol, obesity, poor diet, lack of exercise, and overexposure to ultraviolet radiation. These factors are avoidable or reducible, so they affect incidence at population level. Genetic risk factors are inherited alleles that raise susceptibility to particular cancers, for example BRCA variants linked to breast and ovarian cancer. A person may inherit a risk and still never develop cancer, because risk is probabilistic, not certain. Reducing lifestyle risks lowers, but does not remove, the chance of cancer.

What earns the marks

• Cancer results from uncontrolled cell division caused by changes in DNA, which may form a tumour.
• Lifestyle risk factors include smoking, alcohol, obesity, poor diet, lack of exercise, and ultraviolet radiation.
• Lifestyle factors are largely avoidable or reducible, so they can lower the chance of developing some cancers.
• Genetic risk factors are inherited alleles, such as BRCA variants, that increase susceptibility to particular cancers.
• Risk factors increase probability rather than guaranteeing cancer, so an individual with a genetic risk may never develop the disease.
• A full explanation links a named factor to increased DNA damage or cell division and therefore to a greater chance of cancer.

Common mistakes and how to put them right

• Stating that a risk factor causes cancer directly.

  Put it right by saying it increases the probability of cancer developing.

• Confusing genetic risk with a certainty of inheriting cancer.

  Put it right by explaining that inherited alleles raise susceptibility but do not guarantee the disease.

• Listing infections as lifestyle factors.

  Put it right by recognising that while some infections are risk factors, they are not classified as lifestyle choices.

Exam tips

• Read the command word carefully; if asked to explain, link each factor to DNA changes or uncontrolled cell division rather than just naming it.
• Use the phrase 'increases the risk of' rather than 'causes' when describing any risk factor.
• Include at least one lifestyle factor and one genetic factor when the question asks about both types of risk.