What is chemotherapy?
Chemotherapy literally means 'drug treatment'. However, the term chemotherapy has come to mean a treatment of cancer by using anti-cancer drugs called cytotoxic drugs.
There are other types of anti-cancer drugs. For example: drugs which block the effects of certain hormones are used to treat some cancers; monoclonal antibodies and other types of drugs which affect the immune system are used to treat certain cancers; etc. These other types of anti-cancer drugs are not dealt with further in this leaflet.
What are cytotoxic drugs and how do they work?
Cytotoxic drugs are toxic (poisonous) to cancer cells. They kill cancer cells, or stop them from multiplying. Different cytotoxic drugs do this in different ways. However, they all tend to work by interfering with some aspect of how the cells divide and multiply. For example, some work by affecting the genetic material of the cell directly, others work by blocking cells from using nutrients needed to divide and multiply.
Two or more cytotoxic drugs are often used in a course of chemotherapy, each with a different way of working. This may give a better chance of success than using only one.
There are more than 30 different cytotoxic drugs. In each case the one (or ones) chosen depend on the type and stage of the cancer. Research continues to find new drugs, and better drug combinations. Your doctor will advise the best treatment for your type of cancer based on evidence from the most recent research trials.
Cytotoxic drugs work best in cancers where the cancer cells are rapidly dividing and multiplying. Most normal cells in the body such as muscle cells, heart cells, brain cells, bone cells, etc, do not divide and multiply very often. They are not usually much affected by cytotoxic drugs. However, some normal cells in the body divide and multiply quite rapidly. For example, hair cells, bone marrow cells, and cells lining the mouth and gut. These may be affected by cytotoxic drugs and lead to side-effects (see below). But as a general rule, normal cells can renew themselves better than cancer cells and can usually recover quite well following treatment.
What are the aims of chemotherapy?
Chemotherapy and other treatments may aim to cure the cancer
A cure is the aim in many cases. Some cancers can be cured with chemotherapy alone. Sometimes chemotherapy is used in addition to another main treatment. For example, you may have surgery to remove a tumour but you may also be given a course of chemotherapy after the surgery. This aims to kill any cancer cells which may have spread away from the primary tumour site. Unless treated, these may have developed into tumours at a later time.
Chemotherapy given after a main treatment such as surgery is called adjuvant chemotherapy. Sometimes, chemotherapy is given before surgery or radiotherapy so that these other treatments are likely to work better. Chemotherapy given before another treatment is called 'neoadjuvant chemotherapy'.
Doctors tend to use the word 'remission' rather than the word 'cured'. Remission means there is no evidence of cancer following treatment. If you are 'in remission', you may be cured. However, in some cases a cancer returns months or years later. This is why some doctors are reluctant to use the word cured.
Chemotherapy and other treatments may aim to control the cancer
If a cure is not realistic, with treatment it is often possible limit the growth or spread of the cancer so that it progresses less rapidly. This may keep you free of symptoms for some time.
Chemotherapy may be used to ease symptoms
This is called 'palliative' chemotherapy. Even if a cure is not possible and the outlook is poor, a course of chemotherapy may be used to reduce the size of a cancer. This may ease symptoms such as pain or pressure symptoms from a tumour.
How is chemotherapy given?
The drugs usually need to get into the bloodstream to get to all areas of the body to reach any cancerous cell which may be present.
Intravenous chemotherapy
To get straight into the bloodstream, many cytotoxic drugs are given by injection directly into a vein ('intravenous' injection).
Chemotherapy given by mouth
Some chemotherapy drugs can be taken as tablets or liquids by mouth and are absorbed into the bloodstream from the gut.
Other methods
Drugs usually do not get into the brain or spinal cord very well from the bloodstream. Therefore, to treat some cancers of the brain or spinal cord, drugs are sometimes injected directly into the fluid which surrounds the brain and spinal cord. This is done by a 'lumbar puncture' when a needle is inserted into the space next to the spinal cord in the lower back.醫(yī)學.全在線www.med126.com
In certain situations cytotoxic drugs may be given by injection into a muscle, as a cream which is rubbed onto skin, injected into the chest cavity, or injected directly into a cancerous tumour.
How long is a course of chemotherapy treatment?
Usually a course of chemotherapy is given in 'cycles'. A cycle is a spell of treatment followed by a rest from treatment. For example, you may have a dose of your drug(s) on one day, or several doses over a few days. You may then have a rest from treatment for 3-4 weeks. This allows your body to recover from any side-effects, and gives a chance for damaged normal cells to recover before the next spell of treatment. Treatment cycles are commonly every 3-4 weeks, but vary depending on the cancer being treated and the drugs used.
The length of a full course of treatment is often about six months. So this may consist of about six cycles of treatment over the six months. But a full course of treatment can vary and may be shorter or longer than six months, and consist of fewer or more cycles. It depends on the type of drugs used and the type of cancer.
You may have tests such as scans or x-rays at various times to see how well treatment is working. These can help to guide a doctor as to how long to continue treatment, or even to change the drugs used if the treatment does not seem to be working. You will also have regular blood tests to check on your blood count (see below) and may also have blood tests to check that your liver and kidneys continue to work well and are not being affected by the drugs.
where is chemotherapy given?
Most people have chemotherapy treatment as an outpatient. You may have to spend a few hours at hospital for each dose of treatment. Some treatment cycles require a day or so in hospital as an inpatient.
Some people have some of their chemotherapy treatment at home. They have a catheter inserted into a vein as described above, and wear a small portable device to gently pump a drug solution into the catheter over a set period of time.
What about risks and side-effects from chemotherapy?
Cytotoxic drugs are powerful and often cause unwanted side-effects. Cytotoxic drugs work by killing cells which are dividing and so some normal cells are damaged too. However, side-effects vary from drug to drug. Even with the same drug, different people can react differently. Some people develop more severe side-effects than others who take the same drug. Sometimes, if side-effects are particularly severe, a change to a different drug may be an option.
Some of the most common and important side-effects are listed below. Other side-effects can occur. You should discuss with your doctor the particular risks and concerns for the drugs which are used in your own treatment. Also, you can read a full list of possible side-effects of any drug on the leaflet from the drug manufacturer. This usually comes in the packaging with the drug, and is also available on the internet at www.medicines.org.uk
At the end of this section there is a 'checklist' of symptoms which you should report straight away to a doctor if they occur whilst you are on a course of chemotherapy.
