How does chemotherapy work?
February 3, 2026
Chemotherapy follows a clear procedure. Even though each treatment is individualised, there are fixed steps that provide orientation. This overview shows how the treatment basically works and what all the different approaches have in common.
Chemotherapy involves the use of drugs that directly kill cancer cells and inhibit their growth (cytostatics). It is used for many types of cancer, often in combination with surgery and/or radiotherapy.
Before chemotherapy
Treatment planning begins after the cancer has been diagnosed. Oncologists will discuss which therapy makes sense. Among other things, this takes into account
- Type and spread of the tumour
- Characteristics of the cancer cells
- General state of health
In order to obtain this information, various preliminary examinations and tests, such as biopsies, CT and/or MRI examinations, are carried out. The appropriate medication is then selected on this basis. These decisions are made at a so-called tumour board, a committee of various experts (oncologists, radiation oncologists, radiologists, gastroenterologists and pathologists).
The dosage is then determined individually based on the calculated body surface area. In addition, concomitant medication is determined to prevent side effects such as nausea.
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Chemotherapy
Chemotherapy usually affects the whole body and takes place in so-called cycles. Treatment phases alternate with breaks to allow the body to recover. These cycles can last from weeks to months.
Important points about the process:
- Treatment usually takes place on an outpatient basis in specialised oncology outpatient clinics.
- However, inpatient treatment may be necessary for very intensive therapies, short treatment intervals or for older people.
- The therapies can be administered intravenously (directly into the vein), subcutaneously (as an injection into fatty tissue) or orally (as a tablet)
- Therapy is often administered as an infusion into the vein over a specified period of time. A port is sometimes used for this, a small access under the skin that protects the veins and can be removed again after treatment as part of a minor operation.
Blood values are checked before each session. Depending on the medication, it may be necessary to monitor vital signs such as blood pressure, pulse, temperature and oxygen saturation during treatment.
Specialised nursing staff are present during the treatment and monitor the progress. A session often lasts several hours. During this time, patients can read, sleep or listen to music.
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After the treatment
After every chemotherapy treatment, the body reacts to the therapy. The side effects usually occur on the second or third day after the therapy and usually last for five to six days or even longer. After that, the therapy-related stresses subside until the start of the next therapy.
Side effects can vary greatly from person to person and occur with a time delay and are also highly dependent on the therapy. Common side effects can be, for example
- Tiredness
- Nausea
- Increased susceptibility to infections
- Hair loss
- Changes in skin, nails or taste
Many of these side effects are now easily treatable and subside once treatment is complete.
Regular check-ups take place between treatment cycles. This is to check how well the body is tolerating the therapy. Psychological and emotional aspects are also taken into account.
Read the issue of our magazine kompass on the subject of cancer:
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