How Chemotherapy Treats Cancer

Understanding the Aims, Benefits, Risks, and Side Effects

In This Article

Chemotherapy is a form of treatment that uses a combination of drugs to cure cancer or reduce cancer symptoms. Chemotherapy drugs are cytotoxic (meaning toxic to cells) and target fast-replicating cells in the body. Cancer cells are invariably fast-replicating but so, too, are hair, skin, and gastrointestinal cells. Because of this, chemotherapy drugs can harm both cancerous and normal cells and may cause symptoms like hair loss, skin problems, and nausea.


Chemotherapy is given at different points of cancer treatment and to achieve different goals. The desired outcome can be divided into these four categories:

  • To treat cancer by killing cancer cells: This includes cells in primary tumors and cancer cells that have spread to other parts of the body. Chemotherapy might be the only treatment given or it may be used with other treatments. 
  • To shrink a tumor before surgery: Neoadjuvant chemotherapy is given before surgery or radiation treatment to make the tumor smaller before it is removed surgically. Chemotherapy will then be used to kill any remaining cells.
  • To prevent cancer recurrence: Adjuvant chemotherapy is given to prevent the return of cancer after surgery or radiation therapy by killing any remaining cancer cells.
  •  To relieve symptoms: The goal of palliative chemotherapy is to reduce pain and other symptoms when cancer cannot be cured. It is given to either control or reverse the growth of tumors in people with terminal cancer.

The effectiveness of chemotherapy can vary by the type of cancer being treated. For example, in late-stage cases, chemotherapy tends to be more effective with childhood leukemia and testicular cancer (80% to 90%) and less effective with pancreatic, ovarian, and brain cancer (3% to 6%).

The effectiveness of therapy is referred to as the response rate. The expected outcome is known as the prognosis.


Chemotherapy is typically delivered using a combination of drugs. Most are referred to by acronyms such as CHOP (for the drugs cyclophosphamide, hydroxydaunorubicin, Oncovin, and prednisone) or BEACOPP (bleomycin sulfate, etoposide phosphate, Adriamycin, cyclophosphamide, Oncovin, procarbazine hydrochloride, and prednisone).

Chemotherapy drugs are typically given either intravenously (IV) or by mouth (orally). Other methods of administration are done, albeit less commonly. The frequency and duration of chemotherapy depend on many factors, including the type of cancer you have, the stage of cancer, and your current health.

The oncologist will develop a treatment plan that is based on the type of cancer, stage, other health factors, type of chemotherapy drugs prescribed, and other treatment methods also being used.

Side Effects

How your chemotherapy treatment affects you depends on many factors, such as how aggressive treatment is, overall general health, and what chemotherapy drug is being taken. Several medications can be prescribed to combat many of the side effects of treatment.

Common side effects of chemotherapy include:

The risk of side effects varies from person to person. Some people have minimal side effects, while others may experience moderate to intolerable side effects. Generally speaking, the risk of side effects is greater in people over 70, in those with multiple health concerns, and in cases where aggressive combination therapies are needed.

Keeping a symptom journal is an effective way to keep track of side effects. This can help your doctor decide on the appropriate interventions and whether a dose adjustment is needed. It also helps you remember details you may forget during your appointment.

Questions to Ask

To understand what chemotherapy involves and what to expect, do not hesitate to ask the following questions before treatment begins:

  • What chemotherapy drug is being prescribed?
  • Why was this chemotherapy regimen chosen over others?
  • What is the duration of treatment?
  • How many chemotherapy sessions will I need to undergo?
  • Should someone drive me home after each session?
  • What side effects can I expect?
  • Which side effects are serious and require immediate medical attention?
  • What can I do to manage symptoms?
  • What is the response rate for the recommended therapy?
  • What is my prognosis?
  • How will chemotherapy affect my daily life?
  • What medications do I need to avoid?
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  1. Ashdown ML, Robinson AP, Yatomi-Clarke SL, et al. Chemotherapy for late-stage cancer patients: meta-analysis of complete response rates. F1000Res. 2015;4:232. doi:10.12688/f1000research.6760.1

  2. Radwa L, Sanmugarajah J. The feasibility and tolerability of newer chemotherapy regimens in the adjuvant setting in older patients with breast cancer. J Clin Oncol. 2019;33(15 Suppl). doi:10.1200/jco.2015.33.15_suppl.e12019

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