Definition of "Chemotherapy"

Last modified: 3 days

Chemotherapy (CTx) is Tx of cancer with cytotoxic chemotherapeutic agents. The objective can be either curative or to relieve suffering. It can either be used as a single-agent, or in combination. Chemoradiotherapy (CRT) is the combination of chemo and radio. It can also be used with hyperthermia, and surgery.

Patient information

What is chemotherapy?
They're drugs which are cytotoxic. This means they are toxic to cells.

  • Cancer
  • Other conditions, including:
    • AL amyloidosis
    • Ankylosing spondylitis
    • Multiple sclerosis
    • Crohn's disease
    • Psoriasis
    • Psoriatic arthritis
    • SLE
    • Rheumatoid arthritis
    • Scleroderma
  • Cytotoxic means that it kills cells that divide rapidly, as it is a main property of most cancer cells. This is also what causes the main side effects. Some newer drugs are more targeted (rather than indiscriminately cytotoxic), targetting proteins abnormally expressed in cancer cells and essential for their growth, known as targeted therapy or biologic therapy

Patient information

Wait. Toxic to all cells? Isn't this bad?
No. Only toxic to cells that divide rapidly. Because that's what cancers basically do. It's also what causes their main side effects.

  • Alkylating antineoplastic agents, which are an alkylating agent, that attaches an alkyl group (CnH2n+1) to DNA. Since cancer cells in general proliferate faster and with less error-correcting than healthy cells, cancer cells are more sensitive to DNA damage, e.g. being alkylated. It includes:
    • Nitrogen mustards, including mechlorethamine, cyclophosphamide, melphalan, chlorambucil, ifosfamide, busulfan
    • Nitrosoureas, including N-Nitroso-N-methylurea, carmustine, lomustine, semustine, fotemustine, streptozotocin
    • Tetrazines, including dacarbazine, mitozolomide, temozolomide
    • Aziridines, including thiotepa, mytomycin, diaziquone
    • Cisplatins and derivatives, including cisplatin, carboplatin, oxaliplatin
    • Non-classical alkylating agents, including procarbazine, hexamethylmelamine
  • Antimetabolites, which inhibit the use of a metabolite, which is another chemical that is apart of metabolism. It is often similar ins tructure ot the metabolite it interferes with, e.g. antifolates interfere with the use of folic acid. The presence of antimetabolites can have toxic effects on cells, e.g. halting cell growth and cell division. Examples include:
    • Azathioprine
    • Mercaptopurine
  • Anti-microtubule agents, which block cell growth by stopping mitosis (cell division). It interferes with microtubules (cellular structures that help move chromosomes during mitosis)
  • Topoisomerase inhibitors, which interfere with the action of topoisomerase enzymes (topoisomerase 1 and 2), which are enzymes that control the changes in DNA structure, by catalyzing the breaking and rejoining of the phosphodiester backbone of DNA strands during the normal cell cycle. It includes:
    • Topoisomerase 1 inhibitors, including irinotecan, topotecan, camptothecin, lamellarin D
    • Topoisomerase 2 inhibitors, including etoposide (VP-16), teniposide, doxorubicin (Adriamycin), daunorubicin, mitoxantrone, amsacrine, aurintricarboxylic acid, HU-331
  • Cytotoxic antibiotics, which are drugs that interrupt cell division. It includes:
    • Anthracycline, including doxorubicin, daunorubicin
    • Actinomycin
    • Bleomycin
    • Plicamycin
    • Mitomycin
Side effects
  • Harms rapidly dividing cells, including cells in the:
    • Bone marrow
    • Immune system, causing myelosuppression (decreased production of blood cells), causing immunosuppression
    • Digestive tract, causing mucositis (inflammation of GI lining)
    • Hair follicles, causing alopecia (hair loss)

Patient information

What are the main side effects of drugs that kill rapidly dividing cells?
They can kill cells OTHER than cancer, that rapidly divide. This includes bone marrow. The GI lining. And hair. They all have quick turnover, so they're also targets for these drugs. That's why during chemo treatment you lose all your hair. You can get lots of tummy problems. And have bone problems.

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Definition of Chemotherapy | Autoprac

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