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How does chemotherapy work?

Last Update: January 14, 2016; Next update: 2019.

Besides surgery and radiation, chemotherapies are commonly used to treat cancer. Chemotherapy for cancer treatment uses drugs called cytostatics, which aim to stop cancer cells from continuing to divide uncontrollably. This text explains what goals chemotherapy can have, how it is done, what its side effects are and what can be done against these side effects.

Goals of chemotherapy

Chemotherapy in the treatment of cancer can have different goals. This is why we differentiate between the following types of chemotherapy:

Curative chemotherapy: Curative chemotherapy aims to eliminate all cancer cells from the body and to achieve a permanent cure.

Adjuvant chemotherapy: Adjuvant chemotherapy aims at cancer cells that might be left in the body after surgery, but that cannot be detected. This kind of supportive therapy aims to prevent recurrences.

Neoadjuvant chemotherapy: Neoadjuvant chemotherapy is done before surgery. Some tumors are too big to be directly operated on. Chemotherapy can often shrink the tumor, making it possible to remove it surgically. It may also aim to allow less invasive surgery.

Palliative chemotherapy: Chemotherapy is called palliative when it is no longer possible to remove all tumor cells. Chemotherapy can then help to relieve certain symptoms, to slow down the progress of the disease or to stop it temporarily, and to avoid complications.

How chemotherapy is done

Types of applications

In chemotherapy the body is given medications. This is usually done with an infusion into a vein, but some medications can also be taken as tablets. There are many different cytostatics, which are often given in combination with one another. Because drugs that are given this way travel in the bloodstream, they usually act in all parts of the body. So they can also get to cancer cells that are not detected in examinations, and that can therefore not be targeted with surgery or radiation. Experts also call this kind of therapy systemic treatment.

In rare cases, it is also possible to use local chemotherapy. Then the medications are not given over the bloodstream, but are injected directly into the affected body region, for example the spinal canal. Then the drugs only reach connected areas, such as the brain or the membranes lining the brain and spinal cord. Basal cell cancer, a type of skin cancer, is sometimes treated with chemotherapy applied as a cream or an ointment, which only act locally.

Chemotherapy is often combined with radiotherapy – this is then called radiochemotherapy. Radiotherapy can be done at the same time or after chemotherapy. Some chemotherapeutical drugs only have an effect when they are subjected to radiotherapy. In this case, chemotherapy only acts locally in the places where radiation was applied.

People who get cytostatics over a longer period of time can sometimes get these drugs through a device called a port. A port consists of a small container, which is inserted under the skin in a minor operation, and connects to a large vein with a thin tube. It can remain in the body for as long as treatment lasts. This has the advantage that infusions can be connected to the port and it is not necessary to look for a vein and puncture it for each treatment.

Illustration: Chemotherapy: Infusion with a port

Chemotherapy: Infusion with a port

Chemotherapy cycles

In chemotherapy, cancer is treated with cytostatics at specific intervals. This is also referred to as treatment cycles or treatment schedules. Various factors influence the number of cycles and the intervals between the individual treatments:

  • how long the effect of the administered drug lasts,
  • how much time the body needs to recover, and
  • the overall length of treatment, for example.

Treatment schedules are tested in studies, which allows them to be optimized over time. How exactly a treatment is done not only depends on research results, however, but also on personal wishes and the state of health of the individual person. If chemotherapy is causing severe adverse effects, for example, it can make sense to deviate from the commonly used therapy schedule.

Different tests like blood tests, tissue samples and imaging techniques like computed tomography, for example, help find out whether a tumor responds to the chemotherapy. If this is not the case, other substances can be used for treatment, or treatment can be stopped.

Outpatient and inpatient treatment

Nowadays it is not always necessary to stay in the hospital for a long time to have chemotherapy. One of the reasons is that side effects can now be better controlled. Many hospitals offer outpatient treatments, and many specialist practices can also administer chemotherapy. It is also possible to do chemotherapy with tablets at home. But staying in the hospital can still be required for very intensive treatments. This is the case, for example, when there is a high risk of infection or when it is necessary to do frequent checks, for example of kidney function.

Fear of side effects: Sometimes greater than necessary

Today, many types of cancer can be treated successfully with chemotherapy. However, there is great fear of the adverse effects of the treatment. Cytostatics usually not only attack cancer cells, but also healthy cells that divide quickly. These include blood-producing cells, hair cells, and the cells of the mucous membranes of the mouth and throat area and of the digestive system. This can have short-term effects like hair loss, anemia, nausea, vomiting, diarrhea and infections in the mouth. But these adverse effects can often be prevented or the symptoms can be relieved. Blood transfusions help ease the effects of anemia, which mainly include tiredness and exhaustion. Antiemetic drugs, which work against nausea, can often successfully treat nausea and vomiting. Infections can be prevented and treated with antibiotic or antifungal drugs.

The severity of the adverse effects of chemotherapy will vary from person to person. The side effects also depend on dosage and the drugs that are used. Not all chemotherapies have severe side effects. And hair, mucous membranes, and blood production will recover after the treatment. Adverse effects of chemotherapy can sometimes occur later, particularly in young people. Because chemotherapy might damage semen or eggs, it is recommended to use reliable contraceptives during treatment.

It depends on the kind of therapy, the type of cancer and the treatment schedule, what side effects can occur during chemotherapy, and whether they are long-term or only occur during treatment. 

Sources

  • Andreae S. Lexikon der Krankheiten und Untersuchungen. Stuttgart: Thieme; 2008.
  • Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J. Harrison’s Principles of internal medicine. New York: McGraw-Hill Companies. 18th ed; 2011.
  • Pschyrembel W. Klinisches Wörterbuch. Berlin: De Gruyter; 2014.
  • IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

    Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. We do not offer individual consultations.

    Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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IQWiG (Institute for Quality and Efficiency in Health Care)

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