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Although all treatment using medicines can be termed chemotherapy, the word is most often used to describe treatment by strong cytotoxic drugs for serious diseases such as cancer.
Brought to you by NHS Choices



'Cytotoxic' means that the drug destroys rapidly growing cancer cells. Cytotoxic drugs are useful in the treatment of many forms of cancer. There are over 200 types of cancer and more than 50 chemotherapy drugs currently licensed to treat the disease, either on their own or in combination.

Medicines based on sex hormones are also used to treat cancer, such as tamoxifen for breast cancer. Although they are sometimes referred to as chemotherapy, they are more often known as hormone-therapy drugs.

Chemotherapy is often used as an additional safeguard after surgery or in conjunction with radiotherapy, to destroy any remaining cancer cells and reduce the chance of the cancer returning. Chemotherapy treatment is sometimes able to destroy all the cancer cells present, but this is not the case with all types of cancer. If a cure is not possible, chemotherapy may be given to try to control the disease, or to reduce symptoms and improve quality of life.

How it works

How chemotherapy works

Cytotoxic drugs are designed to cause more damage to cancer cells than to normal body cells, because in most cases the medicines can distinguish cancer cells from other cells by the speed with which cancer cells reproduce. Normally, cells divide and reproduce in an orderly and controlled manner. However, cancer cells multiply without proper control. Chemotherapy works by interfering with the cell reproduction process.

How it is performed

How chemotherapy is performed

Chemotherapy may be given in different ways, depending on the type of cancer you have and the chemotherapy medicines used. It is usually given by injection into a vein (intravenously). Some medicines are given:

  • as tablets or capsules (orally)
  • by injection into a muscle (intramuscular or IM injection), or
  • by injection just under the skin (subcutaneous injection).

Most people have to spend a few hours at hospital for each treatment session. Some may require an overnight stay, and some may have their treatment at home using a small portable device which pumps the medicine solution into their body through an opening in a vein.

Each treatment session is followed by a rest period to allow the normal cells and tissues time to recover. This is known as a cycle of treatment, several of which make up a course of chemotherapy.

Side effects

Side effects of chemotherapy

The ability to distinguish between the two cell types is not complete, and cytotoxic drugs cannot avoid causing some damage to normal cells. The more rapidly normal cells reproduce, the more likely they are to be damaged by cytotoxic drugs. They cause most damage to cells in the lining of the bowel, hair-producing cells, the sex glands and the blood-forming tissue in the bone marrow.

The four most common side-effects are vomiting, hair loss, tiredness and myelosuppression (bone marrow suppression). However, almost all side effects are only short-term and will gradually disappear once the treatment has stopped. Side effects vary depending on the individual response and the type of treatment. Some people experience very few side effects of chemotherapy.

Expert view

Chemotherapy expert Peter Clark on the questions to ask

Peter Clark, consultant medical oncologist at the Clatterbridge Centre for Oncology in Merseyside, answers some key questions on chemotherapy.

What types of chemotherapy are there?
There are four different types of chemotherapy:

  • Curative chemotherapy This is used to try to cure the patient of their particular disease. By cure, we mean that they will live a normal life after the end of treatment.
  • Palliative treatment If the cancer cannot be cured, this type of chemotherapy is used to improve the patient’s quality of life as much as possible, for as long as possible, whether it be for a few months or for a few years.
  • Adjuvant chemotherapy This is given to patients to reduce the risk of the cancer coming back in the future. It's usually given in cases where patients have had surgery where the cancer has been removed.
  • Neoadjuvant Treatment given to patients to improve the results of surgery or radiotherapy that will be performed in the future.

Chemotherapy usually consists of a drip into the bloodstream, but can also be in the form of tablets, or both.

Does chemotherapy involve much pain?
The pain experienced through chemotherapy comes from the needle being put into the vein, so pain isn’t a major part of chemotherapy treatment. It is a similar discomfort to having a blood test.

Will I lose my hair?
The first side effect that many people ask about is hair loss. This varies because some chemotherapy drugs always cause hair loss, some chemotherapy drugs virtually never cause hair loss, and there are some drugs that will sometimes cause hair loss.

Are there any other side effects?
The side effects of chemotherapy are mostly significant in terms of affecting the quality of a patient’s life rather than being physically painful. Throughout the whole of the chemotherapy, we do our best to minimise their impact.

A typical chemotherapy agent will certainly cause tiredness, and there is often a risk of feeling sick, but there are very good anti-sickness drugs these days to keep it under control.

Chemotherapy also frequently causes changes in our ability to taste, as well as soreness in the mouth.

I feel scared at the thought of having chemotherapy. Is this normal?
I think it’s fair to say that everyone is scared when they first come for chemotherapy. They’re faced with a potentially life threatening disease such as cancer, along with a treatment that they’re unfamiliar with.

Can I bring someone with me for support or company?
Coming with a family member is always a good idea because it’s someone who you can share the anxiety with, and someone who can relay what happens to other family members.

Useful links

NHS Choices links

External links

This article was originally published by NHS Choices

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