AQA GCSE Biology 8461: Cancer – Revision Notes

Cancer is the result of changes in cells that lead to uncontrolled growth and division. For AQA GCSE Biology (8461) you must be able to define cancer, compare benign and malignant tumours, explain how malignant cells spread to form secondary tumours, and give lifestyle and genetic risk factors.

These are condensed recall notes for 4.2.2.7 Cancer of the AQA GCSE Biology (8461) specification, Version 1.0, for teaching from September 2016 and exams from 2018 onwards. Organisation is assessed on Paper 1, set at Foundation and Higher Tier. Nothing in 4.2.2.7 is marked (HT only) or (biology only), so every line applies to both tiers. There is no required practical, and cancer treatments are not part of this subtopic.

The normal cell cycle and mitosis are in the Cell division revision notes. Carcinogens and other risk factors are covered alongside other non-communicable diseases in the Health issues and lifestyle revision notes. The course hub is AQA GCSE Biology, and the printable checklist lists every point. To find your weak spots fast, try the free 10-minute diagnostics.

What is cancer?

Cancer is the result of changes in cells that lead to uncontrolled growth and division.

change in a cell (e.g. damage to DNA) -> the cell no longer controls when it divides
-> it divides again and again by mitosis -> a mass of abnormal cells (a tumour)

Normal cells divide only when new cells are needed for growth or repair. Cancer cells keep dividing.

What is the difference between benign and malignant tumours?

	Benign tumour	Malignant tumour
What it is	A growth of abnormal cells	A growth of abnormal cells that is a cancer
Where the cells stay	Contained in one area, usually within a membrane	Invade neighbouring tissues
Spread	Does not invade other parts of the body	Cells break off, travel in the blood, and form secondary tumours elsewhere
Is it cancer?	No	Yes

A benign tumour can still be harmful: a large one can press on an organ (for example in the brain). “Benign” means it does not spread, not that it is always harmless.

Method in steps: describing how a cancer spreads

1. Cells in a malignant tumour divide uncontrollably.
2. They invade the tissue around the tumour.
3. Some cells break away and enter the bloodstream.
4. The blood carries them to other parts of the body.
5. There they settle and divide, forming secondary tumours.

What are the risk factors for cancer?

Scientists have identified lifestyle risk factors for various cancers. Some cancers also have genetic risk factors.

Type	Examples
Lifestyle	Smoking (lung, mouth and throat cancers); obesity (for example bowel cancer); drinking a lot of alcohol (for example mouth and liver cancers); too much exposure to ultraviolet light from the Sun or sunbeds (skin cancer)
Carcinogens in the environment	Ionising radiation (X-rays, gamma rays, radon gas); chemicals such as those in tobacco smoke
Genetic	Inheriting certain alleles makes some cancers more likely, for example alleles of the BRCA genes and breast cancer
Infection	Some viruses living in cells can trigger cancer, for example HPV and cervical cancer

A risk factor raises the chance of a cancer. It does not make the cancer certain.

Worked example: comparing risk. In a study, 18 in every 10 000 people who used sunbeds regularly developed skin cancer over ten years, compared with 6 in every 10 000 people who did not. 18 / 6 = 3, so the sunbed users were three times as likely to develop skin cancer. The data show a correlation; to say UV light causes the cancer you also need a mechanism (UV damages DNA in skin cells) and a large, representative sample.

Must-know distinctions

• Benign vs malignant: stays in one area within a membrane vs invades tissue and spreads in the blood.
• Primary vs secondary tumour: where the cancer starts vs a new tumour formed by cells that spread.
• Tumour vs cancer: malignant tumour cells are cancers, but a benign tumour is not cancer.
• Lifestyle vs genetic risk factor: something you do or are exposed to vs alleles you inherit.

Quick self-test

1. Describe what cancer is.
2. Give two differences between benign and malignant tumours.
3. Which type of tumour cells are cancers?
4. How do malignant tumour cells reach other parts of the body?
5. What is a secondary tumour?
6. Why can a benign tumour still be dangerous?
7. Give two lifestyle risk factors for cancer.
8. Give one example of a genetic risk factor for cancer.

Answers

1. Changes in cells lead to uncontrolled growth and division.
2. Any two: benign cells stay in one area and malignant cells invade neighbouring tissue; benign tumours are usually within a membrane; malignant cells spread in the blood to form secondary tumours, benign do not.
3. Malignant tumour cells.
4. They break away and are carried in the blood.
5. A tumour formed in a different part of the body by cells that spread from a malignant tumour.
6. It can grow large and press on an organ, such as the brain.
7. Any two: smoking; obesity; heavy drinking of alcohol; too much UV exposure.
8. Inheriting certain alleles, for example of the BRCA genes, which raise the risk of breast cancer.

Frequently asked questions

Is every tumour a cancer? No. Only malignant tumours are cancers. A benign tumour is a growth of abnormal cells that stays in one area, usually within a membrane, and does not invade other parts of the body.

How does cancer spread to other organs? Cells break away from a malignant tumour, travel in the blood and settle elsewhere, where they divide to form secondary tumours.

Do I need to know cancer treatments for 8461? No. Subtopic 4.2.2.7 covers what cancer is, the two types of tumour and risk factors. Treatments such as chemotherapy are not part of the specification content.

Where marks are usually lost

• Writing “cells divide” instead of uncontrolled growth and division.
• Saying benign tumours are cancers, or that they spread.
• Saying malignant cells “move” without naming the blood and secondary tumours.
• Giving only lifestyle factors when a question asks about genetic risk factors too.
• Saying that a risk factor always causes cancer.

Official syllabus

AQA GCSE Biology (8461) specification, Version 1.0, for teaching from September 2016 and exams from 2018 onwards (AQA), section 4.2 Organisation: 4.2.2.7 Cancer.