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Cancer health centre

How chemotherapy works

Chemotherapy is one of the most common treatments for cancer. It uses certain drugs to kill cancer cells or to stop them from growing and spreading to other parts of your body. Your doctor might prescribe chemo by itself or together with surgery, radiotherapy, hormone therapy or biological therapy (immunotherapy).

There are different types of drugs you can take, and each one destroys or shrinks cancer cells in a different way. You can take them as tablets, capsules or injections. You might go to hospital so you can get the drugs through a drip, also known as an IV (intravenous infusion).

To help your body regain strength and grow new, healthy cells, you might take the drugs over a few weeks. You might take doses every day, every week, or every month. It depends on the type of cancer you have and how severe it is.

Your cancer doctor, called an oncologist, may prescribe one drug or a mix of different ones, depending on:

Why you need chemotherapy

Even after surgery to remove a tumour, your body might still have living cancer cells. These cells can grow new tumours or spread the disease to other parts of your body.

Chemotherapy drugs help destroy, shrink or control those cells. It might also treat symptoms the cancer causes, like pain. You might also get chemo to shrink a tumour before your doctor removes it during surgery.

How it works

Chemotherapy drugs work in a few different ways. They can:

  • Kill both cancerous and healthy cells.
  • Fight only cancer cells.
  • Keep tumours from growing blood vessels, which help them thrive.
  • Attack the cancer cells’ genes so the cells die and can’t grow into new tumours.
  • Newer medicines use your body’s own immune system to find and destroy cancer cells.

Common chemotherapy drugs

Here are some different types of chemotherapy drugs that your doctor may use:

Drugs that kill cancer cells by damaging their DNA. These drugs, called alkylating agents, are the oldest type of chemotherapy. Some examples are cyclophosphamide, melphalan, and temozolomide. As they kill bad cells, though, they can also destroy your bone marrow in the process, which can cause leukaemia (a blood cancer) years later. To lower this risk, you can take the drugs in small doses. One type of alkylating agent, platinum drugs like carboplatin, cisplatin or oxaliplatin, has a lower risk of causing leukaemia.

Drugs that attack cancer cells during the middle of their growth. They replace their DNA and RNA, genetic codes inside cells, so they stop growing. Doctors call them antimetabolites. Drugs in this group include 5-fluorouracil, 6-mercaptopurine, cytarabine, gemcitabine and methotrexate, among many others.

A type of antibiotic that alters the DNA inside cancer cells (not like the antibiotics used to treat infections), called anti-tumour antibiotics, including actinomycin-D, bleomycin, daunorubicin, doxorubicin and more. They attack the enzymes inside cancer cells that help them divide and grow. High doses of these drugs can damage your heart or lungs. So your doctor will only have you take them for a short time.

Drugs that stop cancer cells from dividing. They can also stop your body from making the proteins that cancer cells need to grow. They’re called mitotic inhibitors, and they include docetaxel, estramustine, paclitaxel and vinblastine.

Another type of medicine, called topoisomerase inhibitors, also attack enzymes that help cancer cells divide and grow. This group includes etoposide, irinotecan, teniposide (which is not licensed in the UK), and topotecan. Some of them, though, may raise your risk of getting a second cancer a few years later.

WebMD Medical Reference

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