Chemotherapy. If you or someone you know has been diagnosed with breast cancer, the chances are that you’ve heard this word spoken in conversation. You may even have an idea of what it entails, but what is it really? How does it work, and how will it affect you or your loved one?

The word chemotherapy means different things to different people. To health care professionals, it refers to any chemical or drug used to treat a symptom of an illness. However, the general public tends to associate the word chemotherapy with the drug treatment regimes specifically used for battling cancer.

While reading literature or talking to health care professionals about chemotherapy for cancer treatment you may also come across the terms antineoplastic and cytotoxic. These words describe the way that chemotherapy drugs act to stop cell replication or even lead to cell death. Additionally, adjuvant chemotherapy is chemotherapy applied after surgery has taken place in order to kill any cells that may have escaped the surgery and entered the bloodstream. Neoadjuvant chemotherapy refers to drug treatment used to reduce the size of a tumor prior to beginning other treatments.

Chemotherapy is a widely used method of cancer treatment primarily due to the fact that it is a systemic treatment. It will affect the entire body. Chemotherapy drugs are usually administered either orally or directly into a vein, which means that they eventually end up traveling through the bloodstream to all areas of the body. This is especially beneficial if cancer has spread from its point of initiation, or metastasized.

Drugs used in chemotherapy are effective primarily because they stop cells from dividing. A normal, healthy cell goes through a replication cycle that includes an internal growth phase in which a second set of proteins, DNA and RNA are made, and a division phase where via a process called mitosis the cell splits in two. This cell division cycle continues until internal controls make the cell stop replicating itself. These controls are damaged or turned off in cancerous cells, so cancerous cells continue dividing indefinitely. Anticancer drugs affect cells at various points in their division cycle, and block cellular instructions for cell division. Research has led to the development of over 100 chemotherapy drugs that affect different stages of the cell division cycle.

One group of drugs work as alkylating agents, and bind directly to DNA at any stage in the cell cycle stopping it from being replicated. Examples of some alkylating drugs used are busulfan, cisplatin, carboplatin, chlorambucil, cyclophosphamide, ifosfamide, dacarbazine (DTIC), mechlorethamine (nitrogen mustard), and melphalan.

Nitrosoureas, like alkylating agents, block DNA replication, but do so by affecting the enzymes involved instead of by attaching to the DNA. These drugs are important due to their ability to gain access to the brain’s blood supply. Two of these drugs are called carmustine (BCNU) and lomustine (CCNU).

5-fluorouracil, capecitabine, methotrexate, gemcitabine, cytarabine (ara-C), and fludarabine are members of a group of drugs known as anti-metabolites. These drugs block DNA and RNA replication during the growth phase of the cell cycle.

Some examples of drugs that stop mitosis directly or indirectly through the inhibition of crucial reproduction enzymes are paclitaxel, docetaxel, etoposide (VP-16), vinblastine, vincristine, and vinorelbine. Interestingly, these drugs come from natural sources and many are actually plant products.

There is also a class of antibiotics that works against tumor growth. These drugs stop replication enzymes and mitosis, and many affect the cell membrane itself to make cell division impossible. Examples of these drugs include dactinomycin, daunorubicin, doxorubicin (Adriamycin), idarubicin, and mitoxantrone.

Sex hormones such as anti-estrogens (tamoxifen, fulvestrant), aromatase inhibitors (anastrozole, letrozole), progestins (megestrol acetate), anti-androgens (bicalutamide, flutamide), and LHRH agonists (leuprolide, goserelin) change the release of male or female hormones in the body, and can affect the growth and development of tumors, which are often hormone responsive. Corticosteroid hormones like prednisone and dexamethasone are sometimes also used to slow the growth rate of some cancers.

Immunotherapy drugs are widely used to stimulate the body’s immune system to attack cancerous cells. There are several compounds like L-asparaginase and tretinoin that do not fit into any of the described categories, but have been shown quite efficacious in treating some cancers. Doctors are able to determine which drugs to use and in what combination based upon the developmental stage of the cancer and personal factors of the patient.

Most of the drugs named above are used in combination with other drugs allowing a multifaceted attack that is specific to the cancer and person being treated. In this way cancerous cells can be stopped, however it is also at the expense of any healthy cells that happen to be dividing as well. Unfortunately, chemotherapy drugs are not specific to only cancerous cells, but to any dividing cells. The death of healthy cells is what leads to the undesirable side effects of chemotherapy such as hair loss, nausea, vomiting, diarrhea, dry mouth, fatigue, and reduced immune function.

Chemotherapy is one of many current treatments for most forms of cancer. It is useful since it can be fine-tuned for each independent patient, and new research is making more drugs and therefore treatment possibilities available. If you have been diagnosed with cancer, use the information that has been included here to assist you in talking to your doctor about determining the best treatment regimen for you.