What is Chemotherapy?

A medical oncologist shares how chemotherapy is used in cancer treatment, the different ways it's used, and what to know about side effects.

In 2024, there will be about 2 million new cancer cases in the United States, according to estimates from the American Cancer Society (ACS). Cancer treatment depends on a variety of factors, but many patients may undergo chemotherapy — medications used to destroy malignant cells in the body — as one way to treat or ease symptoms of cancer, explains Dr. Evelyn Taiwo, a medical oncologist at NewYork-Presbyterian Brooklyn Methodist Hospital and an associate professor of clinical medicine at Weill Cornell Medicine.

“Depending on the cancer type and presentation, a patient will only need to be on chemotherapy, or it may be given in addition to radiation therapy and/or surgery,” she says.

Health Matters spoke with Dr. Taiwo on what to know about this common therapy, including how it works and its side effects.

Dr. Evelyn Taiwo

What is chemotherapy?
Dr. Taiwo: Chemotherapy is a cytotoxic treatment, which are drugs that are given to destroy cancer cells. Cancer cells are easier to destroy because they divide quickly. Chemotherapy drugs have different toxicities and adverse effects. Because they are not targeted drugs, they destroy all cells, including healthy ones. And that is why we see some of the side effects. Generally, we recommend chemotherapy to cure, control, or manage the cancer.

At what point does a patient start chemotherapy?
Once cancer is diagnosed, a patient and their care team engage in shared decision making to decide on next steps and we identify with them what the goal of treatment is. Deciding on the course of treatment depends on the type of cancer the patient has, where the cancer is in the body, size of the tumor, and the patient’s overall health.

How Chemotherapy is Used

A patient receives chemotherapy for different purposes and at varying points, depending on their cancer presentation.

Curative therapy. If a patient has early-stage disease, meaning that the cancer is in the organ, sometimes in the surrounding lymph nodes and has not spread to other organs, they may get chemotherapy with the intent to cure.

Neoadjuvant and adjuvant therapy. When a patient receives chemotherapy before surgery with the purpose of shrinking a tumor and destroying cancer cells, this is referred to as neoadjuvant therapy. Post-surgery, a patient may get adjuvant therapy with the intent of removing any remaining cancer cells.

Maintenance chemotherapy. Maintenance chemotherapy is given when a patient has responded to the first recommended treatment and is considered cured. Research has shown that with certain diseases, continuing treatment for a prolonged period is beneficial to preventing the cancer’s return or delaying the growth of advanced cancer after the initial treatment.

Palliative chemotherapy. If cancer has spread to other organs, patients may get chemotherapy to manage the disease. In these situations, it may help control the cancer, prevent further spread, or shrink the tumor. While it won’t eliminate the cancer, patients can be on this treatment for years.

What are some of the short-term side effects of chemotherapy?
When we are making decisions with patients on potentially putting them on active and often times toxic drugs like chemotherapy, we have conversations with them about the benefits and risks.

There are common side effects patients experience when on chemotherapy. Fatigue is one of them. Nausea and vomiting are also very common. A lot of that has to do with disruption of the lining of the gastrointestinal tract. Those cells are also affected, irritated, and sometimes destroyed by chemotherapy, which is why we sometimes see diarrhea. It is all tied together in terms of nausea, vomiting and diarrhea.

But these are all side effects that we know how to manage. For example, a lot of patients will get nausea medicine before they experience symptoms and have these medications at home to take as needed.

Hair loss is a symptom that many, but not all, chemotherapy drugs cause. We know that hair is very important to patients, so there are ways to mitigate hair loss, such as utilizing scalp cooling devices, which are available at many cancer centers. The goal of that is to shrink the blood vessels in that area to make it difficult for chemotherapy to get to the follicles and cause problems leading to hair loss.

Another symptom is bone marrow suppression. The bone marrow is like the factory where the white cells, red cells, and platelets are made. Because they are very sensitive, they tend to be affected by chemotherapy. To manage that, patients on chemotherapy who have very low white blood count can get injections to boost their white blood cells.

What should patients know about any long-term complications?
Not everyone who undergoes chemotherapy will experience long-term complications but there are some potential ones we discuss with patients. Heart disease occurs in a small number of patients who get a drug called Adriamycin. It is one of the most common chemotherapy drugs that can cause cardiotoxicity. The way we try to minimize this is having a patient’s heart function checked before they start treatment. For those who already have compromised heart function, their care team may choose not to give them this category of chemotherapy drugs. There will be some patients who will still develop heart issues after their treatment. In those cases, patients are referred to and managed by a cardiologist who can monitor their heart.

Infertility is becoming less of an issue now thanks to the growth of fertility medicine. For many of our young patients, if they are going to be getting a treatment that can lower their fertility or cause infertility, we make sure they are seen by a fertility specialist. If desired, there is sperm banking for men. Women can get egg or embryo freezing done before they start treatment. Sometimes we give medications that can help boost their ovarian function at the end of treatment.

How is chemotherapy administered? What is the duration and frequency of treatment?
Chemotherapy can be administered intravenously (IV), orally, or subcutaneously and deciding on which options is based on the best form of how that drug gets into the body. There are some drugs that if they are given orally, they are not able to be broken down to the actual metabolite, which is the active drug. Most of our drugs are still IV but many of the targeted agents tend to be oral. Anti-hormone treatments that are used in breast cancer and prostate cancer have oral forms as well.

How often and how long a patient is on chemotherapy depends on the patient and type of drug.

What should patients keep in mind as they begin their cancer treatment journey?
Ask questions — no question is too simple. Patients should have a sense of, we are doing this together with the physician, who are here to make recommendations and give directions, but the patient is driving the car.

It is important for patients to feel empowered in the decision-making process and to be connected to a mental health expert. Many centers have psychotherapists, psychologists, and social workers where part of the initial consultation is getting a mental wellness assessment to get a sense of what support the patient needs, and if they have spouses or children, to also assess what support their family members need. A lot of people are affected by a cancer diagnosis, not just the patient on their own.

There is a lot of loss of control patients feel when they get a diagnosis. Suddenly, there is a doctor in charge of your life and health decisions for the next few months. So having questions and feeling like you are a team with the doctor is also a way of getting some control back.

Evelyn Taiwo, M.D., is a physician at NewYork-Presbyterian Brooklyn Methodist Hospital specializing in oncology and hematology. She is also an associate professor of clinical medicine at Weill Cornell Medicine.

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