Chemotherapy

Copied from: http://hcd2.bupa.co.uk/fact_sheets/html/chemotherapy.html
Published by BUPA's Health Information Team
February 2004

Chemotherapy is a type of drug treatment used in cancer. There are over 50 different chemotherapy drugs available. The drugs are used in different ways according to the type of cancer, how advanced it is and the general health of the person being treated.

Different chemotherapy drugs may be used alone or in combinations of two or more drugs.

Aims of chemotherapy
Chemotherapy is used at various stages of cancer. It is used to treat solid tumours (cancerous lumps) affecting organs such as the breast or bowel, as well as blood cancers such as leukaemia.

Chemotherapy may be given at one or more of the following stages:

Before surgery (neo-adjuvant therapy) to shrink a tumour so that it is easier to remove from the body. This is normally used for large tumours or those that are strongly attached to surrounding tissue.
After surgery (adjuvant therapy) to make sure that any cancerous cells left in the body after removal of a tumour are killed. This makes it less likely that the cancer will come back.
In advanced cancer to remove cancerous cells that have spread through the body, or to slow the progress of the disease.
Each person has their own chemotherapy treatment planned by an oncologist, a doctor who specialises in treating cancer.

The goal of chemotherapy in people with early cancers is usually to kill the cancerous cells and to cure the condition.

When cancer has spread to other organs, it may not be possible to cure the condition fully. In this case, the aim of chemotherapy may be to slow the progress of the disease and to extend the period of good quality life for as long as possible. This is called palliative chemotherapy.

In some types of cancer, particularly leukaemia, high-dose chemotherapy is used. This treatment also destroys many of the body's own immune cells and has to be followed by a bone marrow transplant, which replaces the tissue damaged by the high dose drugs.

The type of chemotherapy drugs depends on a number of factors:

the type of cancer
where the cancer started
whether the cancer has spread to other parts of the body
the general health of the person
People are monitored regularly throughout their course of chemotherapy by physical examination, X-rays or scans, as well as blood and urine tests.

How chemotherapy works
All chemotherapy drugs work by attacking cells that are dividing rapidly. Normal cells divide at a rate that is tightly controlled by the body. However, in cancer cells, the cell division goes wrong, leading to uncontrolled production of new cells and the formation of a tumour or blood cancer. Chemotherapy drugs interfere with the division of these cells and may cause the cancer to die back completely.

Types of chemotherapy medicines
Most chemotherapy drugs affect the DNA in cancer cells. This is the chemical (made up of two strands of linked molecules) that stores the genetic information in a cell. DNA controls what a cell does, including how it divides.

The main groups of chemotherapy drugs are:

Alkylating drugs, such as cyclophosphamide, stick to one of the DNA strands and prevents them dividing. They are used in breast and lung cancers, as well as some lymphomas and leukaemias.
Cytotoxic antibiotics, such as doxorubicin, stick to DNA causing it to become tangled and preventing the cell from dividing. They are used in breast, ovary, bladder and lung cancers, lymphoma and sarcoma.
Antimetabolites, such as methotrexate, stop cells working by preventing them making and repairing DNA. They are used in breast, bone and bladder cancers, and some leukaemias.
Vinca alkaloids, such as vindesine, disrupt the mechanism that enables one cell to split into two new cells. They are used in leukaemias and lymphomas, as well as in breast and lung cancers.
Other drugs include platinum compounds like carboplatin, and taxanes such as docetaxel. They have various modes of action.
Other cancer drugs
Chemotherapy is not the only type of drug treatment available for cancer. Other treatments, which may be used alongside chemotherapy, include drugs that alter hormone levels in the blood and slow down the growth rate of hormone-dependent tumours (eg some breast cancers).

Several other new treatment options are more experimental and may only be available in clinical trials. They include:

Angiogenesis inhibitors - prevent the growth of blood vessels inside a tumour, starving it of blood.
Biological therapies - help the body's immune system to attack cancer cells.
Monoclonal antibodies - stick to cancer cells and stimulate the body to destroy them.
How are the drugs given?
Most chemotherapy drugs are given directly into the bloodstream. This can be by injection or infusion ("drip") into a vein in the back of the hand, or through a "central line", a thin tube that leads from the skin of the chest to a main vein near the heart. A central line can be left in place for a few months, with drugs injected when required.

Other ways to be given chemotherapy drugs include:

tablets
injections into muscle
injections into the area around the spinal cord (intrathecal injection)
injections into a cavity such as the bladder
injections under the skin
creams for skin cancers
Chemotherapy in the form of tablets or creams can be taken at home. Injections or infusions are usually given on an outpatient basis in a chemotherapy suite at hospital. It is sometimes possible to be given chemotherapy at home. These sessions may take between 30 minutes and a few hours at a time.

Injections into the abdominal cavity usually require a few days' stay in hospital, whereas high-dose chemotherapy followed by a bone marrow transplant needs a stay of a few weeks.

Chemotherapy is often given in combinations of two or more drugs in order to reduce the number of as many cancer cells as possible. Common combinations include cyclophosphamide, doxorubicin, vincristine and prednisolone (often abbreviated as "CHOP") for non-Hodgkin's lymphoma and cyclophosphamide, methotrexate and fluourourcil ("CMF") for breast cancer.

Duration of treatment
The length of chemotherapy treatment depends on the type of cancer, how much it has spread through the body, the types of drugs used, the severity of side-effects and how successful the treatment is.

In most cases, chemotherapy is given in cycles of treatment alternating with rest periods to allow the body to recover from side-effects. Several cycles of treatment are needed, as chemotherapy only attacks cells that are actively dividing. At any one time, some cancer cells will be resting, and may not be killed until a later round of drug treatment.

It may be necessary to change the original ("first-line") course of treatment if this is not controlling the cancer adequately or if there are dangerous side-effects. The new drug or combination is called the "second-line" treatment.

Side-effects
Chemotherapy does not only target cancer cells, but any cells that divide rapidly. This includes those in the bone marrow and skin, hair-producing cells, and the cells that line the mouth and digestive system. Damage to these healthy cells may produce various side effects, including:

tiredness
nausea and vomiting
diarrhoea or constipation
hair loss
getting infections more easily
sore mouth, mouth ulcers and changes in the sense of taste
Many of these side-effects can be controlled using additional drugs. For example, nausea can be reduced using antiemetic (anti-sickness) drugs such as ondansetron or steroids (eg dexamethasone). Furthermore, most side-effects are temporary and will pass once treatment is completed. However, there is a risk that irreversible infertility and, for women, early menopause may occur.

Effects on everyday life
Some people manage to continue with their lives as normal during chemotherapy. A small number of people even feel better as the symptoms of their cancer decrease. However, for many people, chemotherapy can have significant effects on everyday life. In particular, tiredness often prevents patients from carrying on working full time or doing normal levels of physical activity.

Women having chemotherapy should not try to become pregnant during treatment because the chemotherapy drugs can damage the developing baby.

Further information
Cancerbackup
0808 800 1234
http://www.cancerbackup.org.uk