Chemotherapy is cancer treatment with medicines that kill cancer cells or stop them growing; these medicines travel in the blood and reach cancer cells anywhere in the body [1, 3]. It is usually given through a drip (into a vein) or as tablets, in "cycles": a period of treatment followed by a period of rest so the body can recover [1]. Depending on the type and stage of the cancer, the aim is to cure it, to shrink a tumour before surgery (neoadjuvant), to lower the chance of the cancer coming back after surgery (adjuvant), or to control the disease and ease symptoms [1, 2].
Key points
- Chemotherapy cures some cancers even after they have spread: in testicular cancer that has spread, only 1 in 20 people survived before today's medicines; now, with chemotherapy (and sometimes surgery), 8 in 10 survive [7].
- In acute lymphoblastic leukaemia in children, a large study found that about 9 in 10 children were alive 5 years later [8].
- After surgery for breast cancer, suitable chemotherapy lowered the risk of dying from breast cancer by about a third on average [9].
- How bad the side effects are does not show how well the treatment is working; that is shown by examinations, blood tests and scans [1].
How does chemotherapy work, and what does it do to your body?
Cancer cells grow and divide quickly. Chemotherapy medicines kill fast-growing cells or stop them growing [1, 2]. When a medicine is swallowed or injected into a vein or muscle, it enters the bloodstream and reaches cancer cells anywhere in the body [3]. That is why chemotherapy can also destroy cells that are left behind after surgery or that have travelled to other parts of the body [1].
But some healthy cells also divide quickly: the cells lining the mouth and gut, the cells in the bone marrow that make blood, and the cells that make hair grow [2]. Damage to these cells causes side effects such as mouth sores, nausea, hair loss and low blood counts [2]. The rest between cycles gives the body time to build new healthy cells [1], and most side effects get better or go away after treatment ends [2].
Chemotherapy may be the only treatment, but it is more often given together with surgery, radiotherapy, targeted therapy or immunotherapy [2]. To learn how it differs from radiotherapy, read: Chemotherapy or radiotherapy: what is the difference?
What are adjuvant and neoadjuvant chemotherapy? The aims of chemotherapy
| Aim | What it means | Example |
|---|---|---|
| Cure | Destroying cancer cells to the point where they can no longer be found in the body and do not come back [2] | Testicular cancer, Hodgkin lymphoma and acute lymphoblastic leukaemia in children [3, 7, 8] |
| Before surgery (neoadjuvant) | Shrinking a tumour before surgery or radiotherapy [1] | In breast cancer, more women were able to have only the tumour removed instead of the whole breast [10] |
| After surgery (adjuvant) | Destroying cancer cells that may be left in the body after surgery or radiotherapy [1] | In breast cancer, it lowered the risk of dying from the cancer by about a third [9] |
| Controlling cancer that has spread | Stopping further spread, slowing growth or destroying cancer cells that have travelled to other parts of the body [2] | In advanced lung cancer, it helped people live longer [11] |
| Palliative | Shrinking tumours that are causing pain or pressure, to ease symptoms [1, 2] | A tumour that presses on an organ and causes pain [2] |
| Maintenance | Continuing one medicine after the first cycles so that cancer that is under control takes longer to grow again [12] | In one type of lung cancer that had spread, continuing one of the medicines helped people live longer [12] |
One course of chemotherapy can have more than one aim; ask your doctor what the aim of your treatment is.
Neoadjuvant vs adjuvant chemotherapy: before or after surgery?
In some cancers, such as breast cancer, the same chemotherapy can be given before or after surgery. In a large review of 10 studies of nearly 5,000 women, the long-term results of the two approaches were the same: the risk of the cancer spreading and the risk of death were almost equal [10].
Chemotherapy before surgery shrank or removed the tumour in more than 2 out of 3 women, and more women were able to keep their breast [10]. On the other hand, the cancer came back in the same area slightly more often; that is why the researchers stressed marking the exact site of the tumour, careful examination of the tissue removed and appropriate radiotherapy after surgery [10].
Chemotherapy is sometimes given at the same time as radiotherapy to help the radiotherapy work better [2]. Whether chemotherapy comes before or after surgery depends on the type and stage of the cancer; read more: What are cancer stages?
How is chemotherapy given?
Chemotherapy can be given in several ways [1]:
- Drip (into a vein): the most common way. At the start of each session a nurse puts a thin needle into a vein in your hand or lower arm and removes it at the end [1].
- Port or catheter: a thin tube placed in a large vein, often in the chest, so that a new needle in the arm is not needed each time; sometimes a small portable pump continues the medicine outside the hospital [1]. Read: Caring for a port or PICC line.
- Tablets, capsules or liquids: some chemotherapy medicines are taken by mouth at home [1].
- Injection into a muscle or under the skin [1].
- Special routes: into the fluid around the brain and spinal cord, into the abdomen, into the artery that feeds the tumour, or as a cream rubbed onto the skin [1].
Where? Chemotherapy may be given as an outpatient (without staying overnight), during a hospital stay or at home [1].
How often? Chemotherapy is given in cycles: for example, one week of treatment followed by three weeks of rest, which together make one 4-week cycle. The rest gives the body time to recover and build new healthy cells [1]. The number of cycles depends on the type and stage of the cancer and the aim of treatment [1]: How many chemotherapy sessions will I need? To work out your treatment dates: Chemotherapy calendar.
How are the medicines chosen? According to the type of cancer and how far it has grown, any chemotherapy you have had before, and other illnesses such as diabetes or heart disease [1]. Before your first session, read: Your first chemotherapy session: what to expect
Can chemo cure cancer?
It depends on the type of cancer and its stage [2]. When we say chemotherapy has "cured" a cancer, we mean the cancer cells have been destroyed to the point where the doctor can no longer find them in the body and they do not come back [2].
- Cancers that chemotherapy often cures, even after they have spread: in testicular cancer that has spread, 8 in 10 people now survive, and in those with lower-risk disease more than 9 in 10 are cured [7]. In acute lymphoblastic leukaemia in children, about 9 in 10 children were alive 5 years later [8]. Hodgkin lymphoma can also usually be cured if it is found and treated early [3].
- After surgery: chemotherapy destroys cancer cells that are left behind [1]; for example, in breast cancer it lowered the risk of dying from the cancer by about a third [9].
- In many cancers that have spread, the aim of chemotherapy is to control the disease: to stop it spreading further, slow its growth and ease symptoms [2]; for example, in advanced lung cancer chemotherapy helped people live longer [11]. Read more: What is metastasis, and can it be treated?
Ask your doctor: "Is the aim of this chemotherapy to cure the cancer, to control it or to ease symptoms?" [2]
How is chemotherapy different from targeted therapy, immunotherapy and hormone therapy?
| Treatment | How it works | When it is used |
|---|---|---|
| Chemotherapy | Kills fast-growing and dividing cells, including cancer cells, or stops them growing [1] | In many types of cancer, alone or with other treatments [1] |
| Targeted therapy | Targets particular proteins in cancer cells that control how they grow and spread; chemotherapy, by contrast, often kills all fast-dividing cells [4] | Mostly when a test of the tumour shows that it has a target for the medicine [4] |
| Immunotherapy | Helps the body's immune system fight cancer [5] | In some cancers, alone or together with chemotherapy [2, 5] |
| Hormone therapy | Slows or stops the growth of cancers that need hormones to grow [6] | Breast and prostate cancers that use hormones to grow [6] |
These treatments are often combined [2]. Read more: What is targeted therapy for cancer?, What is cancer immunotherapy? and Chemotherapy or targeted therapy?
Chemotherapy side effects in brief
The most common side effect is tiredness (fatigue) [1]. Other common side effects are nausea and vomiting, low blood counts, hair loss, mouth sores and pain [2]. You may have many side effects, a few or none at all; this depends on the type and amount of medicine and how your body reacts [2]. Most side effects go away after chemotherapy ends, but sometimes this takes months or even years, and some, such as damage to the nerves, the heart or fertility, may be permanent [2].
Read more: What are the side effects of chemotherapy?, When do chemotherapy side effects start, and how long do they last?, Nausea and vomiting, Hair loss, Low blood counts and preventing infection and Fatigue.
When should I call my doctor?
During chemotherapy, call your treatment team straight away in these situations, even at night or at the weekend [2]:
- A temperature of 38°C or higher (or whatever temperature your team has told you), chills or sweats; talk to your team before taking any medicine that lowers fever, even paracetamol (acetaminophen) or ibuprofen [2]
- Cough, burning or frequent urination, earache, headache or a stiff neck [2]
- Redness, swelling, pain or discharge around a port or catheter [2]
- Vomiting for more than a day, or bringing up everything you drink [2]
- Diarrhoea for more than 24 hours, or diarrhoea with pain and cramps [2]
- Pain or burning where the needle goes in during an infusion: tell the nurse at once [2]
If you suddenly feel very unwell, for example with severe breathlessness or confusion, call your local emergency number. Read more: Fever and warning signs during chemotherapy.
Frequently asked questions
Is there chemotherapy in tablet form?
Yes. Some chemotherapy medicines are tablets, capsules or liquids taken at home [1]. It is best not to miss any doses; if side effects make it necessary, your doctor will change the schedule [1]. Read more: Chemotherapy tablets at home: how they compare with drips, and staying safe
What does palliative chemotherapy mean? Does it mean there is no hope?
Palliative chemotherapy is given to ease symptoms, for example by shrinking a tumour that is causing pain or pressure [2]. It does not mean giving up on treatment. In many cancers that have spread, chemotherapy controls the disease and slows its growth [2]; for example, in advanced lung cancer it helped people live longer [11].
What is maintenance chemotherapy?
Sometimes, after the first cycles, if the cancer is under control, one of the medicines is continued so that the cancer takes longer to grow again. In a study of one type of lung cancer that had spread, continuing the medicine pemetrexed after the first 4 cycles delayed the growth of the cancer and helped people live longer [12].
If I have no side effects, does that mean the chemotherapy is not working?
No. Side effects have nothing to do with how well chemotherapy is fighting the cancer; severe side effects do not mean it is working better, and having none does not mean it is not working [1].
Can chemotherapy be given at home?
Sometimes, yes: tablets are taken at home, and sometimes a small portable pump continues the medicine at home after the session [1]. After each chemotherapy treatment, you and your family need to avoid contact with your body fluids (urine, stools, vomit, blood) for a while; ask your team how long [2]. Read more: Is chemotherapy dangerous for the people around me?
Are chemo and radiation the same?
No. Chemotherapy uses medicines [1], which travel in the blood to the whole body [3]; radiotherapy uses radiation. To learn how they differ and which is used for which cancer, read: Chemotherapy or radiotherapy: what is the difference?
Evidence on the aims of chemotherapy (for doctors)
For physicians
- Adjuvant chemotherapy in breast cancer (EBCTCG 2012): individual-patient-data meta-analysis of 123 trials and about 100,000 women. Compared with no chemotherapy, the breast cancer mortality rate ratio (RR) was 0.64 with CAF, 0.78 with standard 4AC and 0.76 with standard CMF; adding 4 cycles of a taxane to a fixed anthracycline-based regimen gave an RR of 0.86. Taxane-plus-anthracycline or higher-cumulative-dose anthracycline regimens reduced breast cancer mortality by about one third on average, with proportional reductions little affected by age (up to at least 70 years), nodal status, tumour size, oestrogen receptor status or tamoxifen use; the absolute benefit depends on the baseline risk [9].
- Neoadjuvant vs adjuvant (EBCTCG 2018): 4,756 women in 10 trials (81% anthracycline-based, median follow-up 9 years). Complete or partial clinical response 69%; breast-conserving therapy 65% vs 49%. 15-year local recurrence 21.4% vs 15.9% (rate ratio 1.37; 95% CI 1.17–1.61), with no difference in distant recurrence (38.2% vs 38.0%), breast cancer mortality (34.4% vs 33.7%) or death from any cause (40.9% vs 41.2%) [10].
- Advanced disease (NSCLC): in an individual-patient-data meta-analysis of 16 trials (2,714 patients), adding chemotherapy to supportive care gave a hazard ratio for death of 0.77 (95% CI 0.71–0.83) and increased 12-month survival from 20% to 29%; the effect did not clearly depend on the drugs used or on single-agent versus combination treatment [11].
- Maintenance (PARAMOUNT): 939 patients with advanced non-squamous NSCLC received 4 cycles of pemetrexed–cisplatin; 539 without progression and with ECOG 0–1 were randomised 2:1 to pemetrexed 500 mg/m² on day 1 every 21 days or placebo. HR for progression 0.62 and HR for death 0.78 (95% CI 0.64–0.96); median overall survival 13.9 vs 11.0 months [12].
- Cure in disseminated disease: in metastatic testicular cancer, cisplatin, vinblastine and bleomycin raised the cure rate from 5% to 60%; in good-prognosis disease, 3 cycles of BEP or 4 cycles of EP cure more than 90% of patients, and about half of those not cured by initial BEP are cured by high-dose salvage chemotherapy with tandem stem cell transplant [7]. In acute lymphoblastic leukaemia in children and adolescents (21,626 patients in COG trials), 5-year survival rose from 83.7% in 1990–1994 to 90.4% in 2000–2005 [8].
References
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Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
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