Chemotherapy: How it works and its side effects

What is chemotherapy?

Chemotherapy is the use of drugs to treat any disease. However, most people solely associate the term with the use of drugs to destroy cancer cells.

Unlike surgery and radiotherapy, which remove, kill, or damage cancer cells in a localized area, chemo can work throughout the body. The treatment can, therefore, kill cancer cells that have metastasized from the primary tumor to other parts of the body.

What does chemotherapy do?

Doctors may recommend chemotherapy to:

• Cure cancer as the primary or sole treatment.
• Reduce the risk of metastasis by stopping or slowing cancer growth.
• Prevent cancer recurrence by killing any cancer cells that may remain after other treatment such as surgery.
• Shrink tumors before other treatments are applied to boost their outcome.
• Ease cancer symptoms by shrinking tumors that are causing pain and other problems.

How chemotherapy works

Chemotherapy drugs work by stopping or slowing the growth of cancer cells. They target the cells at different phases of the cell cycle, which is the process of producing new cells. Cancer cells tend to grow and divide rapidly, making them a better target for chemo drugs.

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The drugs, however, can’t tell healthy cells and cancer cells apart. As a result, healthy cells also get damaged during treatment, which causes side effects. Therefore, whenever doctors give chemo, they must try to cure or manage cancer with minimal side effects.

Types of chemotherapy

There are over a hundred different chemotherapy drugs. Certain factors can be used to group these drugs, including how they work and their chemical structure. Some drugs work in more than one way hence may belong to more than one group.

Knowing how each drug works is essential in predicting its side effects, which helps doctors decide which drugs are likely to work well together. And if more than one drug is used to treat cancer, the information also helps plan the order in which the drugs will be given and how often.

Alkylating agents

Alkylating agents prevent cells from reproducing by damaging their DNA. They work in all phases of the cell cycle and are used to treat various cancers, including:

• Lung, breast, and ovary cancers
• Leukemia
• Lymphoma
• Hodgkin disease
• Multiple myeloma
• Sarcoma

Examples of alkylating agents include:

• Busulfan (Myleran)
• Cyclophosphamide
• Chlorambucil
• Thiotepa
• Altretamine
• Temozolomide (Temodar)
• Carmustine
• Lomustine
• Carboplatin
• Cisplatin
• Oxaliplatin

Caution: Alkylating agents can affect the cells of the bone marrow, which can lead to leukemia. The risk of leukemia from these drugs is, however, dose-dependent, meaning it increases as the dosage gets higher.

Antimetabolites

Antimetabolites interfere with DNA and RNA synthesis by acting as false metabolites. They attack cells during the phase cells’ chromosomes are copied. Antimetabolites are used to treat:

• Leukemia
• Cancers of the breast, ovary, and intestinal tract

Examples of these agents include:

• Methotrexate
• 5-Fluorouracil (5-FU)
• Floxuridine
• Cytarabine (Ara-C)
• Capecitabine (Xeloda)
• Gemcitabine (Gemzar)
• 6-Mercaptopurine (6-MP)
• Fludarabine

Antitumor antibiotics

Antitumor antibiotics work by altering the DNA inside cancer cells to keep them from growing and multiplying. The medicines are used to treat many types of cancers. There are several types of antitumor antibiotics:

• Anthracycline: Doxorubicin (Adriamycin PFS, Adriamycin RDF), Daunorubicin (Cerubidine, Rubidomycin), Epirubicin, and Idarubicin
• Anthracenedione: Mitoxantrone
• Chromomycin: Dactinomycin (Cosmegen) and Plicamycin
• Miscellaneous: Mitomycin and Bleomycin

Caution: Anthracyclines can permanently damage the heart if given in high doses.

Topoisomerase inhibitors

Topoisomerase inhibitors interfere with the action of topoisomerase enzymes, which help separate DNA strands for replication. These drugs are used to treat:

• Leukemia
• Lung, ovarian, gastrointestinal, and other cancers

They are grouped based on which type of enzyme they affect. The two groups are:

• Topoisomerase I inhibitors: Irinotecan (Camptosar), Topotecan (Hycamtin)
• Topoisomerase II inhibitors: Etoposide (VP-16), Teniposide, Amsacrine, and Mitoxantrone.

Caution: Topoisomerase II inhibitors can increase the risk of a second cancer called acute myelogenous leukemia (AML) within 2 to 3 years.

Mitotic inhibitors

Mitotic inhibitors are drugs derived from natural plant products. They work by inhibiting mitosis (cell division) in the M phase of the cell cycle or, damaging cells in all stages by preventing enzymes from making proteins needed for cell reproduction. The drugs are used to treat a variety of cancers, including:

• Myelomas
• Lymphomas
• Leukemias
• Breast and lung cancers

Examples of mitotic inhibitors include:

• Docetaxel (Taxotere)
• Eribulin (Halaven)
• Estramustine
• Ixabepilone (Ixempra)
• Paclitaxel (Taxol)
• Vinblastine
• Vincristine

Caution: They are more likely than other types of chemotherapy to cause painful nerve damage.

Corticosteroids

Corticosteroids, often known as steroids, are synthetic hormone-like drugs used in the treatment of various cancers and other illnesses. When prescribed as part of your cancer treatment, corticosteroids are considered chemotherapy drugs. They help to:

• Control and prevent nausea and vomiting caused by chemo
• Reduce swelling and pain caused by cancer
• Prevent severe allergic reactions to chemo

Example of the drugs include:

• Prednisone
• Methylprednisolone (Solumedrol)
• Dexamethasone (Decadron)

Miscellaneous chemotherapy drugs

Some chemotherapy drugs are unique and do not fit well into any of the other categories. These include:

• Ribonucleotide reductase inhibitor: Hydroxyurea
• Adrenocortical steroid inhibitor: Mitotane
• Enzymes: Asparaginase and Pegaspargase
• Antimicrotubule agent: Estramustine
• Retinoids: Bexarotene, Isotretinoin, Tretinoin (ATRA)
• Proteasome inhibitor: Bortezomib (Velcade)

How is chemotherapy given?

You may be given chemotherapy in various ways, which include:

• Oral: the chemotherapy comes in pills, capsule, or liquids which you swallow.
• Intravenous (IV): the chemo drug is put right into your bloodstream through a catheter inserted into a vein in your forearm or hand.
• Intrathecal (IT): the chemotherapy is put into the spinal canal and goes into the fluid that surrounds the brain and spinal cord.
• Intra-arterial: chemo drugs are injected directly into the artery that supplies blood to the tumor.
• Intracavitary: the chemo drug goes directly into an enclosed area of the body, such as the abdomen (intraperitoneal chemo) or chest (intrapleural chemo).
• Intramuscular (IM): the chemotherapy is injected right into a muscle.
• Intralesional: a needle is used to put the chemo directly into a tumor.
• Intravesical: chemo drugs are put right into the bladder through a catheter.
• Topical: the chemotherapy comes in a cream, gel, or ointment that you rub onto your skin.

Where do you go for chemotherapy?

Where you get your treatment depends on which chemo drugs you’re getting, the dosage, your hospital’s policies, your insurance coverage, what your doctor recommends, and your preferences. You may receive chemotherapy:

• At home
• In a hospital
• In a clinic
• In a doctor’s office
• In a hospital’s outpatient infusion center

Depending on individual facilities, some may have private treating rooms, while others treat patients in one large area. Consult your doctor on the matter ahead of time, so that you know what to expect on the first day.

Which chemotherapy drugs will you receive?

As we discussed earlier, there are many different chemotherapy drugs. Your doctor will decide which ones to include in your treatment plan depending on:

• The type of cancer you have and how advanced it is
• Whether you have had chemo or other cancer treatments before
• Your overall health
• The treatment goal
• Your preferences

How often will you receive chemotherapy and for how long?

How often you get chemo and how long your treatment lasts depends on:

• The type of cancer you have
• The stage of the cancer
• The goal of the treatment
• The type of chemotherapy you’re receiving
• How your body responds to the chemo

You may receive chemotherapy daily, weekly, or monthly, but it’s usually in on-and-off cycles. For example, you may get treatment every day for one week and then have three weeks off. In this scenario, four weeks make up one cycle. The time off allows your body to recover and build new cells.

Your cancer team should have the details on the number of cycles planned for your treatment and how long it’s expected to last.

As for how long chemo drugs remain in the body, It takes about 48 hours for your kidneys and liver to break down and or get rid of most chemo drugs. But ensure to confirm with your doctor since the body takes longer to excrete some drugs.

Chemotherapy side effects

Chemotherapy not only kills fast-growing cancer cells but also kills or slows the growth of fast-growing healthy cells. Normal cells likely to be damaged by chemo are:

• Cells that line your mouth and intestines
• Blood-forming cells in the bone marrow
• Hair follicles

Damage to healthy cells causes side effects, such as mouth sores and nausea. Many side effects go away fairly quickly, but some might take months or years to go away completely.

Some side effects can also last a lifetime, such as infertility and long-term heart or lung damage. Additionally, some chemo drugs can cause delayed effects such as a second cancer years later.

Common side effects of chemotherapy drugs include:

• Fatigue
• Hair loss
• Nausea and vomiting
• Diarrhea
• Infections
• Easy bruising and bleeding
• Anemia
• Mouth, tongue, and throat problems, such as sores and pain when swallowing
• Skin and nail changes, such as dry skin and color change
• Loss of appetite
• Chemo brain, which is characterized by memory or concentration problems
• Fertility problems

Side effects vary from person to person, even among those receiving the same type of chemotherapy. Moreover, some people experience few to no side effects.

Ask your cancer care team about the most common side effects of the chemo you’ll receive, how long they might last, their severity, and when to contact your doctor. Your cancer care team will also help you manage any side effects you experience.

What is the cost of chemotherapy?

The cost of your chemotherapy will depend on:

• The type and dosage of chemo you receive
• How often and how long you’ll receive chemo
• Whether you’ll get chemo at home or in a hospital, clinic, or doctor’s office
• Where you live

Most insurance plans pay for chemotherapy. But talk with your health insurance provider to find out the specific details about their chemotherapy medical coverage.