Chemotherapy is a type of cancer treatment, with medicine used to kill cancer cells. It kills the cancer cells by damaging them, so they can't reproduce and spread.

Why chemotherapy is used

Chemotherapy is used if a cancer has spread or if there's a risk that it will. The main aim of treatment may be:

• to try to cure cancer completely – this is known as curative chemotherapy
• to help make other treatments more effective – for example, chemotherapy can be combined with radiotherapy (where radiationis used to kill cancerous cells), or it can be used before surgery
• to reduce the risk of the cancer returning after radiotherapy or surgery
• to relieve symptoms – a cure may not be possible for advanced cancer, but chemotherapy may be used to relieve the symptoms and slow it down; this is known as palliative chemotherapy

Less commonly, chemotherapy is used to treat non-cancerous conditions. For example, low doses have been used to treat lupus andrheumatoid arthritis.

How chemotherapy is used

There are many different types of chemotherapy medication, but they all work in much the same way. Depending on the type of cancer you have, you may be treated with one medicine (monotherapy) or with a combination of medicines (combination therapy).

There are several ways in which chemotherapy medication can be given, including tablets and injections directly into a vein.

The team caring for you will help come up with a treatment plan for your specific circumstances.

Side effects

Even though chemotherapy is often effective at treating cancer or relieving its symptoms, it does cause side effects.

The medicines used in chemotherapy can't distinguish between fast-growing cancer cells and other types of fast-growing cells, such as blood cells, skin cells and the cells inside the stomach.

This means that most chemotherapy medications have a poisonous effect on the body's cells, causing problems including:

• feeling tired and weak all the time
• feeling and being sick
• hair loss

Some people only have minimal side effects, but for most people, a course of chemotherapy can be unpleasant and upsetting.

Living with and adapting to the side effects of chemotherapy can be challenging. However, it's important to realise that most, if not all, side effects will disappear once the treatment is complete.

There is no risk of the side effects of chemotherapy being passed to other people, including children and pregnant women, if they are in close contact with someone having chemotherapy.

Targeted therapies

In the past, any medication used to treat cancer was regarded as chemotherapy. However, over the last 20 years, new types of medication that work in a different way to chemotherapy have been introduced.

These new types of medication are known as targeted therapies. This is because they're designed to target and disrupt one or more of the biological processes that cancerous cells use to grow and reproduce.

In contrast, chemotherapy medications are designed to have a poisonous effect on cancerous cells.

Chemotherapy for colorectal cancer

There are three ways chemotherapy can be used to treat bowel cancer:

• before surgery – used in combination with radiotherapy to shrink the tumour
• after surgery – to reduce the risk of the cancer recurring
• palliative chemotherapy – to slow the spread of advanced bowel cancer and help control symptoms

Chemotherapy for bowel cancer usually involves taking a combination of medications that kill cancer cells.

They can be given as a tablet (oral chemotherapy), through a drip in your arm (intravenous chemotherapy), or as a combination of both.

Treatment is given in courses (cycles) that are two to three weeks long each, depending on the stage or grade of your cancer.

A single session of intravenous chemotherapy can last from several hours to several days.

Most people having oral chemotherapy take tablets over the course of two weeks before having a break from treatment for another week.

A course of chemotherapy can last up to six months, depending on how well you respond to the treatment.

In some cases, it can be given in smaller doses over longer periods of time (maintenance chemotherapy).

Side effects of chemotherapy can include:

• fatigue
• feeling sick
• vomiting
• diarrhoea
• mouth ulcers
• hair loss with certain treatment regimens, but this is generally uncommon in the treatment of bowel cancer      
• a sensation of numbness, tingling or burning in your hands, feet and neck

These side effects should gradually pass once your treatment has finished. It usually takes a few months for your hair to grow back if you experience hair loss.

Chemotherapy can also weaken your immune system, making you more vulnerable to infection. Inform your care team or GP as soon as possible if you experience possible signs of an infection, including a high temperature (fever) or a sudden feeling of being generally unwell.

Medications used in chemotherapy can cause temporary damage to men's sperm and women's eggs. This means there's a risk to the unborn baby's health for women who become pregnant or men who father a child. It's recommended that you use a reliable method of contraception while having chemotherapy treatment and for a period after your treatment has finished.

The content is offered for informational and educational purposes only, and is not intended to be a substitute for medical advice, diagnosis or treatment.