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Understanding How Chemotherapy Treats Cancer

Published July 2, 2012

Written by Joann Jovinelly | Reviewed by George Krucik, MD

When a person has cancer, abnormal cells in his or her body develop rapidly and at a much faster rate than healthy cells. If your doctor detects cancer, he or she will recommend different treatment combinations that may include surgery, radiation, and/or chemotherapy. Treatment decisions depend on many factors, including the type of cancer you have, your age, and your overall health. Not all cancers are treated with chemotherapy, which can be administered intravenously, by injection, topically, or orally.

Chemotherapy is a drug treatment used to slow or completely stop the rapid growth of abnormal cancer cells. Unfortunately, traditional chemotherapy treatments also destroy the body's healthy cells in that process. That cell destruction causes many side effects, such as damage to the stomach and throat as well as those responsible for hair growth. Side effects vary and may be reduced or eliminated by switching to a different chemotherapy drug, using a lower dose of the same chemo drug, or combining chemo drugs with other medications. Most side effects disappear after chemotherapy treatments are stopped, though some, such as fatigue, may linger. Other lasting side effects from chemotherapy may include an elevated risk of heart disease.

According to Dr. Matthew M. Cooney, oncologist at the University of Ohio Seidman Cancer Center, chemotherapy is a treatment that's personalized for each patient. "The important thing to remember about chemotherapy is that there are many, many different types of cancer and likewise, literally dozens of different kinds of chemotherapy [drugs]. Sometimes patients think that their chemotherapy treatment will be exactly like a relative's experience who had chemo, but that's [typically] not true at all," he explains.

In some cases, chemotherapy cannot cure cancer completely; sometimes it is used to slow the growth of abnormal cancer cells throughout the body wherever they have spread, or it may be used to reduce symptoms, such as shrinking a cancerous tumor so it no longer causes pain.

Side Effects

Although traditional chemotherapy remains an excellent weapon in the fight against cancer, the treatments, which are given in cycles, can be very hard on the body. (A cycle of chemotherapy is a treatment period followed by a rest period to give the body time to recover. For example, a typical chemo cycle is one week on the chemo drugs followed by three weeks off.)

Chemotherapy can cause a vast array of side effects like nausea, vomiting, hair loss, exhaustion, constipation, bleeding problems, fluid retention, mouth sores, and the risk of infection. Fortunately, physicians are well aware of the side effects and can usually combine chemo drugs with other agents to reduce symptoms, switch to a lower (less toxic) dose, or change drugs altogether.

According to Dr. Cooney, one [lesser-known] side effect of chemotherapy is neuropathy, or numbness and tingling of the hands and feet. "Neuropathy can be quite disabling for many patients and it last a long time. Another side effect is persistent fatigue, not just during the chemotherapy itself, but many patients report fatigue for prolonged periods of time after treatment. In women, chemotherapy treatments may affect the ovaries and/or contribute to earlier menopause. In men, chemotherapy may affect the testicles, testosterone levels, and even cause erectile dysfunction. For younger men and women who undergo chemotherapy, there's also a risk of infertility."

Targeted Chemotherapy

Medical advancements in cancer treatment have improved vastly during the last decade. Today, traditional chemotherapy is rarely used on its own. Instead, traditional chemotherapy drugs are often combined with cytotoxic chemotherapy, a class of drugs that destroy cancerous growths while leaving healthy cells unharmed. These advanced treatments target individual types of cancer, and it rarely causes the same unwanted side effects that traditional chemotherapy does.

According to Dr. Cooney, "Many of the newer cytotoxic chemotherapy drugs are targeted agents that block a specific function of the cancer cells, but do not harm normal cells." Targeted chemotherapy drugs have been developed for specific types of lung cancers, breast cancers, colon and prostate cancers, and others. Still more are in development, awaiting approval through the U.S. Food and Drug Administration.

Some targeted chemotherapies are so specifically tailored to a patient's cancer type that they may only be used if that patient's tumor tests positive for specific gene mutation, as is the case for some forms of breast and lung cancers. Dr. Sylvia Adams, spokesperson for the American Society of Clinical Oncology (ASCO) and assistant professor in NYU's Langone Medical Center in New York City explains that the newest [cytotoxic] drugs offer "a more patient-focused approach that targets [chemotherapy] treatments to the genetic abnormality in cancers that drive cancer growth."

"There are certain cancers that we can examine molecularly to find a specific genetic abnormality to them," says Dr. Cooney, "so we can identify more exactly which genes are involved. There are also a handful of cancers that the genetic change makes a difference in what medications would be best at fighting them. For example, in certain types of lung or colon cancer, there are genetic changes that we can identify will likely respond better to targeted medications. In those cases, doctors are tailoring their treatment plan according to past results. [Targeted] treatments are becoming more common, but unfortunately we do not yet have genetic testing for every type of cancer."

Targeted chemotherapies are also helping those with advanced cancers live months and even years longer than before while maintaining a better quality of life. In those examples, the cancers may not be completely eliminated, but these drugs keep abnormal cell growth at bay by blocking one or more functions of the damaged cancer cells.

Other developments in targeted chemotherapy reported from the 2012 ASCO Conference include "dozens of smart-bomb medications" that combine cancer-cell bonding antibodies with toxins that can only be released after they attach to cancer cells. In this scenario, even healthy cells near the tumor site remain unharmed during treatment. However, only those who have undergone specific tests on their cancerous cells may benefit from targeted medications, as only genetic testing can determine if you have any of the cancer types for which they are suited. Your oncologist can explain if any targeted chemotherapy drugs are available to treat your cancer and how they might benefit you if used along with traditional chemotherapy.


  1. Informed Health Online. (2012). How Does Chemotherapy Work? http://www.ncbi.nlm.nih.gov/books/NBK91404/
  2. The American Cancer Society. (2012). Chemotherapy Principles: An In-Depth Discussion. http://www.cancer.org/Treatment/TreatmentsandSideEffects/TreatmentTypes/Chemotherapy/ChemotherapyPrinciplesAnIn-depthDiscussionoftheTechniquesanditsRoleinTreatment/chemotherapy-principles-how-does-chemo-work
  3. MayoClinic.com. (2012). Cancer: Can Chemotherapy Side Effects Increase the Risk of Heart Disease? http://www.mayoclinic.com/health/chemotherapy-side-effects/AN01407
  4. Dr. Cooney, Matthew M., Medical Director, Ambulatory-Based Programs, University of Ohio Seidman Cancer Center, Cleveland, Ohio. Personal interview. 7 June 2012.
  5. National Institute of Health staff writers. (2012). New Personalized Drugs Show Promise Against Melanoma, Lung Cancer. Medline Plus. http://www.nlm.nih.gov/medlineplus/news/fullstory_125877.html
  6. Marilynn Marchione/Associated Press (2012). Cancer Advances: New Drugs and ‘Smart Bombs' on the Horizon. Time Magazine. http://healthland.time.com/2012/06/04/cancer-advances-new-drugs-and-smart-bombs-on-the-horizon/
Content written and reviewed by Healthline

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