Chemotherapy is the use of chemical agents to kill cells. In conversational usage, the term chemotherapy refers to the chemical treatment of cancer. But chemical agents are also used to treat multiple sclerosis (MS), various autoimmune diseases, and even arthritis.
Most people associate chemotherapy with a myriad of horrible side effects, such as hair loss and nausea. While these side effects do often accompany chemo regimens, millions of cancer patients have been able to enjoy long, vibrant lives because of this treatment option. Furthermore, chemotherapy side-effect management has progressed significantly over the past few decades. Many of chemo’s distressing side effects can be prevented completely, or controlled using today’s advanced treatment strategies.
More than 50% of people diagnosed with cancer are treated with chemotherapy. For some patients, chemo serves as their only treatment, whereas other patients are prescribed chemotherapeutic drugs alongside other treatment options.
How Does Chemo Work?
Chemotherapeutic drugs inhibit the process of mitosis, or cell division. Since malignant (cancer) cells divide without control or order, these drugs effectively target cancerous growths. Some chemo drugs cause cancer cells to die altogether by stimulating a process known as apoptosis (programmed cell-death).
Although chemotherapeutic drugs are designed to target fast-dividing cancer cells, they inadvertently damage healthy cells. The faster a healthy cell divides, the more likely it is to be affected by chemo. This is why your hair may fall out during a chemo regimen. The cells that compose the hair follicles divide quickly.
Researchers have yet to determine all of the features unique to malignant cells and healthy cells. Identifying these specific features may someday open the door to chemotherapeutic drugs that target malignant cells exclusively, resulting in little to no side effects.
Chemotherapeutic drugs have been developed to target various rates of mitosis (cell division), but the slower the rate of division, the greater the risk of healthy cell damage. It is easier to differentiate aggressive malignancies from normal tissues, than it is to target a slow-growing malignancy in an environment of similarly slow-growing healthy cells. This makes aggressive cancers the best candidates for successful chemo treatment.
The Focus of Chemotherapy Treatment
Depending on the type, size, and location of your cancer, as well as your overall health, a doctor may focus chemotherapy to achieve any of the following goals:
- Curative: Curative chemotherapy is intended to kill all the cancer cells in the body, curing the patient of cancer.
- Palliative: This approach involves prolonging the patient’s life by controlling cancer growth, spread, and invasion into other tissues. Palliative treatments are also used to help relieve cancer-related symptoms, improving the patient’s quality of life.
- Adjuvant: This treatment strategy involves using chemotherapy alongside other cancer treatment options. Adjuvant chemotherapy is usually administered after surgery or radiotherapy to kill any remaining cancer cells in the body.
- Neoadjuvant Chemotherapy: The focus of neoadjuvant chemotherapy is to reduce the size of a tumor preceding surgery or other treatment options.
Types of Chemotherapy
Chemotherapy drugs include:
ALKYLATING AGENTS
These chemical agents utilize the cellular property of electronegativity to add alkyl groups to cells. Electronegativity is a cell’s ability to attract electrons. When a cell inadvertently attracts alkyl groups, the alkyl alters the cell’s DNA, resulting in cell death or impaired mitosis.
The following chemotherapeutic drugs are alkylating agents:
- Cisplatin
- Carboplatin
- Oxaloplatin
- Mechlorethamine
- Cyclophosphamide
- Chlorambucil
ANTI-METABOLITES
These chemical agents mask themselves as purine (one of the building blocks of DNA). When a cell accepts the masked anti-metabolites, it becomes unable to incorporate genuine purine into its DNA. This results in cellular DNA damage. Anti-metabolites are among the most widely used chemotherapeutic drugs.
PLANT ALKALOIDS
These chemical agents are derived from plant cells. They inhibit microtubule function in a cell. Microtubules are the structural components of a cell that are responsible for mitosis, among other cellular functions.
ANTITUMOR ANTIBIOTICS
These chemical agents involve the patient’s own immune system in the inhibition of mitosis. Examples of these chemotherapeutic drugs include:
- Trastuzumab (Herceptin)
- Cetuximab
- Rituximab
Side Effects of Chemotherapy
Although side effect management has come along way in recent years, chemotherapy drugs still affect healthy cells. Sometimes the effects of cell damage are temporary, but sometimes they are long-term or even permanent. Talk to your doctor about what to expect from your chemotherapeutic drugs.
SHORT-TERM SIDE EFFECTS
- Hair Loss
- Bleeding
- Fatigue
- Infertility
- Cognitive Impairment
- Sensory Abnormalities: Food tastes different, odors are perceived differently, etc.
- Lung Damage
- Nervous Tissue Damage
- Liver Damage
- Gastrointestinal Damage: Damage to the fast-dividing cells of your gastrointestinal tract (stomach, intestines, esophagus, and other digestive components) may result in a myriad of side effects, such as:
Temporary effects may include:
- Nausea
- Vomiting
- Diarrhea
- Dry Mouth
- Constipation
- Mouth Sores
- Difficulty Swallowing
- Loss of Appetite
The onset of these symptoms may also be the result of cellular damage elsewhere in the body.
Most of these side effects will diminish or disappear completely after you stop your chemo treatments. There are medications available to accompany your chemo treatments that may help reduce the negative effects of chemotherapy.
LONG-TERM SIDE EFFECTS
Long-term Chemo effects are rare. As cancer patients live longer and longer lives, doctors are uncovering side effects that don’t show until many years after treatment ends. Discuss the possibility off long-term effects with your doctor before beginning any treatment.
Long-term effects may include:
- Nervous Tissue Damage: This may result in sensory abnormalities and impaired cognitive function. This is rare.
- Hematuria: Blood in the urine.
- Organ Damage: This typically involves heart, lung, or kidney impairment.
- The Onset of Another Cancer: Studies have suggested a link between chemotherapy and the onset of Hodgkin’s disease, non-Hodgkin’s lymphoma, and leukemia. This link has not been properly identified, but it is probably due to the cellular DNA damage caused by chemotherapy.
History of Chemotherapy
In the 1940s, the United States Department of Defense recruited two pharmacologists, Louis S. Goodman and Alfred Gilman, to research the therapeutic properties of chemical warfare agents. Autopsy findings involving people exposed to nitrogen mustard (mustard gas) unveiled conditions in the body conducive to tumor suppression.
Goodman and Gilman first began testing the effects of nitrogen mustard on mice. These tests allowed them to officially demonstrate the antitumor properties of nitrogen mustard. After the mice tests, Goodman and Gilman collaborated with thoracic surgeon Gustav Linskog to inject mustine (a molecular variation of nitrogen mustard) into a human with non-Hodgkin’s lymphoma. This caused the patient’s malignant masses to decrease in size. The patient was not cured, but this was a major stepping-stone in the treatment of cancer with chemical agents.
After World War II, the scientific community embarked on a number of cancer treatment research projects. These projects included the groundbreaking use of folate analogues to treat Indian children with leukemia in 1948. Folate anologues antagonize folic acid in cells. Folic acid is a vital component of cellular metabolism. When cellular metabolism is impaired, cellular division is disrupted, or the cell dies. Using folate analogues was the first demonstration of remission in all patients that were given the chemical agent.
In the 1950’s, the U.S. government began incentivizing pharmaceutical companies to develop anticancer drugs. Since this initial “push” to support cancer research and drug development, cancer has been receiving an enormous amount of political and social attention around the world. This much-needed attention has led to many breakthrough tests and treatment options.
The Future of Chemotherapy
The future of chemotherapy involves the development of chemical agents that can target malignant cells more precisely. This will reduce or eliminate healthy cell damage, resulting in fewer side effects. Researchers are also hard at work developing chemotherapy drugs aimed at treating slow-growing malignancies that are currently less sensitive to chemical agents.
