Chemotherapy is the use of medication (chemicals) to treat disease. More specifically, chemotherapy typically refers to the destruction of cancer cells. However, chemotherapy may also include the use of antibiotics or other medications to treat any illness or infection.
This article concentrates on chemotherapy for cancer treatment. Cytotoxic medication prevents cancer cells from dividing and growing. When health care professionals talk about chemotherapy today, they generally tend to refer more to cytotoxic medication than others.
After a military operation in World War II some sailors were accidentally exposed to mustard gas. They were later found to have very low white blood cell counts. White blood cells usually grow very quickly - cancer cells also divide and grow very quickly.
The doctors wondered whether the effect of mustard gas - slowing down the rapid growth of white blood cells - may have the same effect on cancer cell growth.
Doctors tried testing patients with advanced lymphomas by injecting a chemical in mustard gas. Even though the effect was temporary, the patients did experience a remarkable improvement.
This led to research into other substances that might slow down or stop the division and growth of cancer cells. Over the decades several new improved drugs were created.
There are more than 100 different types of chemotherapy drugs today which can treat most cancers.
Genetic testing is helping doctors target chemotherapy more accurately. Testing for genetic mutations can help identify breast cancer patients who will not benefit from a specific type of chemotherapy, scientists from the USA and Norway reported.
By studying the patterns in which light bounces off the surfaces of cells, researchers may be able to assess chemotherapy's success in triggering cancer cell death, according to a study led by investigators in the Duke Comprehensive Cancer Center and Duke's Pratt School of Engineering.
Chemotherapy is often used alongside other treatments. Doctors and patients should take physical exercise seriously, because of the benefits for many cancer patients. Patients who regularly exercise after chemotherapy treatment have a much lower risk of cancer recurrence, compared to people who are physically inactive, researchers from the University of Nebraska reported at The Integrative Biology of Exercise VI meeting in October 2012. They say their findings may help investigators understand why exercise may greatly reduce the risk of secondary cancer in survivors. They added that physical activity can also lower the chances of ever developing cancer among those who have never had the disease.
Chemotherapy has five possible goals
- Total remission - to cure the patient completely. In some cases chemotherapy alone can get rid of the cancer completely.
- Combination therapy - chemotherapy can help other therapies, such as radiotherapy or surgery have more effective results.
- Delay/Prevent recurrence - chemotherapy, when used to prevent the return of a cancer, is most often used after a tumor is removed surgically. Scientists at the Charite School of Medicine, Germany, found that the use of the drug gemcitabine for chemotherapy significantly delays the recurrence of cancer, compared to no chemotherapy.
- Slow down cancer progression - used mainly when the cancer is in its advanced stages and a cure is unlikely. Chemotherapy can slow down the advancement of the cancer.
- To relieve symptoms - also more frequently used for patients with advanced cancer.
How does chemotherapy work?
When our body cells are damaged or die we produce new ones to replace them. This is done in an orderly way, in a balanced way. Cancer cells do not have that orderly capacity - their reproduction (division and growth) is out of control - more and more of them are produced and they start to occupy more and more space, until eventually they push out space occupied by useful cells.
Chemotherapy (chemo) drugs interfere with a cancer cell's ability to divide and reproduce. Chemo drugs may be applied into the bloodstream to attack cancer cells throughout the body, or they can be delivered directly to specific cancer sites.
Chemotherapy drugs work in various ways:
- Impairing mitosis (prevent cell division) - these are known as cytotoxic drugs.
- Targeting cancer cell's food source, enzymes and hormones they require in order to grow.
- Stopping the growth of new blood vessels that supply a tumor. In a study, researchers at the Johns Hopkins University School of Medicine discovered how a whole class of commonly used chemotherapy drugs can destroy cancer by blocking blood vessel growth.
- Triggering suicide of cancer cells - cell suicide is known medically as apoptosis.
Patients may receive monotherapy or combination therapy:
- Monotherapy - the patient is given just one drug.
- Combination therapy - the patient receives more than one drug.
Which type the patient receives will depend on the kind of cancer the patient has, as well as some other health considerations.
Chemotherapy may be given at different stages
- Neo-adjuvant therapy - if the tumor is large the surgeon may want to shrink it before surgery. This may involve some pre-operative chemotherapy and/or radiotherapy.
- Chemoradiation therapy - the chemotherapy is given in combination with radiotherapy. Patients with localized Hodgkin's lymphoma where the tumor is situated above the diaphragm should be given chemotherapy combined with radiotherapy, European scientists reported after carrying out a clinical trial. Another study reported that the solid tumor cells that survive chemoradiation therapy often end up stronger than they were before.
- Adjuvant therapy - chemotherapy given after surgery. The use of chemotherapy following surgery reduces the risk of death from operable pancreatic cancer by around 30%, a UK study found.
Often age will determine whether chemotherapy should be used at all for patients with certain cancers. Researchers at The Mayo Clinic, USA, found that the combination of chemotherapies 5FU and oxaliplatin compared to 5FU alone after surgery for colon cancer decreases colon cancer recurrence and promotes longer survival for patients under 70 - but not for those who are older.
How long is a course of chemotherapy?
In the majority of cases for best results the patient will need regular chemotherapy over a specific period. A protocol plan is drawn up which specifies when treatment sessions will occur and for how long.
A course of chemotherapy may be just a one-day treatment, or can last for a few weeks - it will depend on the type and stage of the cancer (how advanced it is). If the patient requires more than one course of treatment there will be a rest period for his/her body to recover. This could be a one-day treatment followed by a week's rest period, followed by another one-day treatment followed by a three-week rest period, etc. This may be repeated many times.
How many health care professionals are involved in chemotherapy treatment?
This will depend on working practices of your hospital, or even the country you live in. In most countries there will be a multi-disciplinary team who treat the patient's cancer. These may include:
- A clinical oncologist - a doctor who specializes in cancer but does not do surgery. He/she is specialized in chemotherapy.
- A cancer nurse - probably the first person the patient will meet when coming in for chemotherapy.
- A hematologist - this is a doctor who is specialized in the study of blood and bone marrow.
- A pathologist - this is a doctor who specializes in the identification of diseases by examining cells and tissues under a microscope.
- A psychologist - he/she will help the patient deal with the mental and emotional ordeal of chemotherapy.
Blood tests before and during chemotherapy treatment
Blood tests are needed to assess the health of the patient as well as ensuring that he/she will be able to cope with possible side-effects. For example, blood tests can detect liver problems, which could mean that chemotherapy is unsuitable for the patient unless the liver recovers. Chemotherapy chemicals are metabolized (broken down) in the liver which could be harmed if it is not working properly.
Before chemotherapy it is important to test the patient's blood count because the treatment will reduce the number of red and white blood cells, as well as platelets. If a blood test reveals a low blood count the doctors may decide to delay treatment.
Researchers at the Paul Papin Cancer Center in Angers, France, reported that measuring drug levels in patients' blood and adjusting them for optimal dosing can substantially reduce severe toxicity and improve efficacy in colorectal cancer.
Regular blood tests will continue during the treatment period so that the medical team can keep an eye on blood count and the state of the patient's liver. As you may read under side-effects further down this page, there is a risk that chemotherapy may lower white, red, and platelet blood level counts.
Monitoring the patient's blood can also provide doctors with important data on how well the chemotherapy is working.
Two ways of giving chemotherapy
Depending on the type of cancer, chemotherapy may be administered orally or intravenously (directly into the vein).
Oral chemotherapy (swallowing tablets)
These will be in the form of tablets. If the patient's health allows it he/she will be able to take them at home. However, regular hospital visits will still be needed to check on the patient's health and response to treatment.
It is vital that the tablets be taken exactly when specified. If the patient forgets to take one at a specific time he/she should call the medical team immediately.
Intravenous chemotherapy (straight into the vein)
Intravenous chemotherapy may be given as:
- An injection straight into a vein.
- Through a drip (intravenous infusion).
- Through a drip or pump.
- Through a pump that the patient wears for several weeks or months. This is called continuous infusion, protracted venous infusion, or ambulant infusion (meaning the patient can walk about while receiving the medication).
There are different ways of getting the medication into the patient. These include:
A cannula - a thin tube is inserted through the skin into the vein - usually it enters the body via the back of the hand or the lower arm.
A drip (intravenous infusion) - in order to dilute the medication it may be injected into a bag. The solution in the bag will pass through a tube into the patients arm and into a vein (intravenous infusion). A cannula will be used. The solution will enter the vein slowly.
Chemotherapy through a drip generally is pushed through with a pump. The pump does not hurry the process up, rather it makes sure the solution enters the vein at a constant rate over a specific period - the slower the rate, the longer the whole thing will take.
A central line - this is a long, flexible, plastic line (thin tube) which ends up in a central blood vessel in the chest, close to the heart. The central line usually enters the body through the center of the chest and goes up under the skin into a large vein by the collarbone (clavicle). The only visible part is the length of line that hangs out of the small entry hole in the chest.
A peripherally inserted central catheter (PICC) line - a long, thin, flexible tube that is inserted into a peripheral vein, usually in the upper arm and makes its way into a large vein in the chest near the heart. It is similar to a central line but has a different point of entry.
A portacath (implantable port) - a thin, soft, flexible plastic tube goes into a vein. It has a port (opening) just under the skin of the chest or arm. The port has a thin rubber disc which special needles can pass medicines into, or take blood from.
Chemotherapy, pregnancy and contraception
Many chemotherapy drugs may cause birth defects. It is important that a woman undergoing chemotherapy avoids becoming pregnant. As most chemotherapy medications interfere with oral contraceptives it is important to use a barrier method of contraception, such as condoms, during the whole chemotherapy treatment period and for a year after treatment is completed. If you are pregnant you need to tell the medical team straight away beforehand. If you become pregnant during treatment tell the medical team straight away.
On the next page we look at the side effects of chemotherapy, protecting the gut from chemotherapy and we look at some of the latest research developments within the area of chemotherapy, including a study which suggests you may wish to avoid eating herring and mackerel in the 48 hours surrounding chemotherapy.