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How Chemotherapy Works

written by: Rose Kivi • edited by: Emma Lloyd • updated: 3/28/2011

A common question people with cancer have is, "How does chemotherapy work?" Find out how chemotherapy works, how it is administered and the role chemotherapy has in cancer treatment

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    What are Cancer Cells

    To understand how chemotherapy works you need to understand what cancer cells are and how they function. Cancer cells are normal cells that have mutated and act abnormally. Normal cells follow a controlled system of division and death. Old and damaged cells die and are replaced by new healthy ones. The normal cells only divide and create new cells when they are needed by the body. Cancer cells have damaged genetic material that cause mutations which affect division and death. The mutated cells do not die when they should and they rapidly divide, creating numerous copies of damaged cells in the body.

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    How Does Chemotherapy Work

    Most chemotherapy drugs work by stopping rapidly dividing cells from multiplying. The drugs do this by interrupting the cells ability to create DNA during division. Without DNA formation, the cells are not viable. Chemotherapy drugs only work against cells that are newly forming. Cells that are in a resting stage and not dividing, are not affected. Basically, chemotherapy does not technically kill cells, it stops new cells from correctly forming.

    Because chemotherapy only affects dividing cells, leaving resting cells unaffected, multiple chemotherapy treatment sessions are required. The idea is that continuing chemotherapy treatments will catch previous resting cells during the division stage.

    There are over 100 types of chemotherapy drugs. Some affect different cells than others and some interrupt cell division in different ways. Doctors sometimes administer multiple types of chemotherapy drugs to a patient in an attempt to better attack cancer cells.

    Side-effects from chemotherapy occur because chemotherapy does not differentiate between normal cells and cancer cells. Normal rapidly dividing cells are affected as well. Examples of rapidly dividing cells are hair follicles, cells that line the inside of the mouth and cells that line the inside of the intestines, are affected. This is why chemotherapy treatment can cause side-effects of hair loss, mouth ulcers and intestinal upset.

    How chemotherapy is administered and how often depends on the type of cancer and its severity. Chemotherapy is usually administered intravenously, but it is sometimes given through an injection or orally. Treatments may be administered daily, weekly or monthly. Usually, chemotherapy is given in treatment cycles, allowing for breaks between treatment to allow normal cells in the body to recover. For example, chemotherapy may be given once a day for three weeks, with a two week break, followed by another three weeks of treatment.

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    The Role of Chemotherapy Treatment

    The purpose of chemotherapy treatment is dependant on the type and stage of cancer. Chemotherapy may be used as a sole treatment for cancer or it may be combined with radiation, other types of drugs, or surgery. Depending on the patient, the role of chemotherapy treatment may be to shrink cancerous tumors before surgery, to kill remaining cancer cells after surgery or to slow the growth of advance stage cancerous tumors to make the patient more comfortable and to extend life.

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    References

    Oncology Nursing Secrets; Rose A. Gates RN MSN CNS NP PhD(c) and Regina M. Fink RN PhD FAAN AOCN; Aug 6, 2007

    National Cancer Institute: Defining Cancer - http://www.cancer.gov/cancertopics/cancerlibrary/what-is-cancer

    American Cancer Society: Chemo - What It Is, How It Helps - http://www.cancer.org/Treatment/TreatmentsandSideEffects/TreatmentTypes/Chemotherapy/WhatItIsHowItHelps/chemo-what-it-is-questions-about-chemo