Chemotherapy: How does it work and how is it given?

What is it?

Chemotherapy is drug treatment that aims to disrupt the growth and division of cancer cells. Because the drugs can enter the bloodstream, they can reach tumour cells in different parts of the body; this is why it is called systemic treatment.

The goal is not the same for every patient. In some cases the aim is to shrink the tumour, in others to reduce cells that may remain after surgery or radiotherapy, and in others to keep the disease under control and relieve symptoms.

How does it work?

Cancer cells divide more often than healthy cells. Chemotherapy drugs disrupt this process by affecting DNA synthesis, the cell skeleton or the stages of cell division. Platinum compounds such as cisplatin and carboplatin, taxanes such as paclitaxel and docetaxel, antimetabolites such as fluorouracil, capecitabine and gemcitabine, and anthracyclines such as doxorubicin are examples that act at different points.

Healthy but rapidly dividing tissues can also be affected. Blood cells, the lining of the mouth and gut, and hair roots are therefore common sites of side effects. The choice of drug, its dose and the interval are adjusted according to guidelines and the person’s organ function.

In which cancers is it used?

Chemotherapy can be part of the treatment plan in lung, breast, colorectal, stomach, pancreatic and ovarian cancer, in many lymphomas and in other tumours. In some cancers it is used alone, in others together with targeted drugs or immunotherapy.

Which treatment is appropriate is discussed at the tumour board, with the relevant specialties taking part, by considering the type, stage and molecular features of the cancer and the person’s general condition together.

How is it given?

Many protocols are given intravenously in a day-treatment unit. Some drugs are tablets or capsules taken by mouth. A break is taken between courses for recovery; the total duration can be weeks or months.

Before each administration, the blood count and kidney and liver tests are reviewed. Supportive steps such as nausea prophylaxis and, when needed, a growth factor are written into the plan from the start. The dose may be postponed or reduced according to side effects or laboratory results.

During follow-up, blood tests, imaging and symptom review are read together. The dose or date may be changed according to side effects and organ function. The list of medicines used at home is updated at every visit. Sudden fever, shortness of breath, uncontrolled diarrhoea or bleeding should be reported the same day.

Possible side effects

Nausea, fatigue, changes in appetite, hair loss, constipation or diarrhoea, mouth sores and susceptibility to infection may occur. Some drugs have their own specific effects: for example, some platinum compounds can affect nerve endings and some anthracyclines the heart. These effects do not occur in everyone and most are managed with supportive treatment.

Symptoms such as fever, shortness of breath, uncontrolled diarrhoea, bleeding or chest pain should be assessed the same day. Where to go for which symptom is discussed before treatment starts.