Section 1 of 9Uncontrolled cell division
Normally the cell cycle is carefully controlled, so that new cells are produced only when needed for growth or to replace damaged cells. Cancer is the result of changes in cells that lead to uncontrolled growth and division by mitosis.
- which is why cancer is more common in older people.
Section 2 of 9Benign and malignant tumours
| Feature | Benign tumour | Malignant tumour |
|---|---|---|
| Location | Stays in one place, often within a membrane | Invades neighbouring tissues |
| Spread | Does not spread to other parts of the body | Cells break off, enter the blood and form secondary tumours elsewhere |
| Danger | Usually not cancer; can cause harm only by pressing on organs | Cancerous, can be life threatening |
| Example | A wart or a benign growth in the breast | Lung or skin cancer |
Cancer is the name for the disease caused by malignant tumours. When cancer cells travel in the blood to other parts of the body and start new tumours, this spreading is called metastasis, and it makes cancer much harder to treat.
Section 3 of 9Risk factors
Some cancers have a strong inherited element, so a person with certain faulty genes is at higher risk. For example, mutations in the BRCA genes increase the chance of breast cancer. Many cancers are linked to lifestyle and the environment:
Reducing exposure to these risk factors reduces the chance of developing cancer, although it can never remove it altogether. Many cancers are caused by a combination of genetic and lifestyle factors.
Not every person exposed to a risk factor develops cancer, which is why scientists speak in terms of increased risk.
Section 4 of 9Detection and treatment
Early detection improves the chance of survival, because the cancer is smaller and has not yet spread. Screening programmes, such as scanning for breast or cervical cancer, look for early signs in healthy-looking people. Treatment depends on the type and stage of the cancer:
- Because they also affect healthy dividing cells, there are side effects such as hair loss and tiredness.
New treatments include drugs that target the cancer cells specifically; monoclonal antibodies (covered later in this course) are one example.
Section 5 of 9Links to other topics
Cancer is a failure of the control of mitosis (see cell division).
- and that organisms need ways of removing damaged cells.
Section 6 of 9Why cancer is more than one disease
There are over 200 types of cancer because tumours can start in almost any tissue, and each behaves differently.
- and doctors often combine surgery with radiotherapy or chemotherapy.
Section 7 of 9Exam-style questions
Explain the difference between a benign tumour and a malignant tumour. [3]3 marks
A benign tumour grows in one place and does not invade other tissues [1]. A malignant tumour invades neighbouring tissues [1], and cells can spread in the blood to form secondary tumours in other parts of the body [1].
Explain why chemotherapy causes hair loss. [2]2 marks
Chemotherapy drugs kill rapidly dividing cells [1]. Hair follicle cells divide quickly, so they are also damaged [1].
Suggest why the survival rate for a cancer is higher when it is found early. [2]2 marks
The tumour is small and has not spread to other organs [1], so it can be removed by surgery or treated before secondary tumours form [1].
Section 8 of 9Key terms
| Term | Meaning |
|---|---|
| Cancer | A disease caused by uncontrolled cell division that forms malignant tumours. |
| Tumour | A mass of abnormal cells. |
| Benign tumour | A tumour that stays in one place and does not invade other tissues. |
| Malignant tumour | A tumour whose cells invade tissues and spread to other parts of the body. |
| Metastasis | The spread of cancer cells to form secondary tumours. |
| Radiotherapy | Treatment of cancer using radiation. |
| Chemotherapy | Treatment using drugs that kill dividing cells. |