What Is Chemotherapy? An Oncologist Explains

Here’s how this cancer-fighting treatment works.

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When you think of cancer treatment, the first thing that may come to mind is chemotherapy. That’s because chemotherapy has been a cancer-fighting mainstay since it was invented in the 1940s.

Chemotherapy, often called “chemo,” is an attractive option for treating cancer because it’s a systemic treatment, as opposed to a local treatment. A local treatment (such as surgery or radiation) removes, kills, or damages cancer cells in a certain area and doesn’t mess with the rest of the body. A systemic treatment targets cancer cells that are spread all over the body, according to the American Cancer Society.

Systemic treatments are effective—and necessary—in later stages of cancer treatment if the cancer has metastasized, or spread, beyond the original tumor site. As a systemic treatment for cancer, chemotherapy can help eliminate the traveling cancer cells throughout the body and help prevent cancer recurrence.

Even though there are newer therapies available today, the type of cancer treatment a patient gets is dependent on the type of cancer the patient has. Many times, chemo is still the best treatment option. Chemo is also often used in conjunction with the other therapies to boost their effectiveness.

How Chemotherapy Works

There are more than a hundred different types of chemo. These therapies differ in their chemical composition, how they are taken, their usefulness in treating specific forms of cancer, and their side effects.

As a class of drugs however, they all focus on one thing: killing rapidly dividing cells. Cancer cells tend to form new cells more quickly than normal cells, which makes them a better target for chemotherapy drugs. Chemo kills these rapidly dividing cancer cells in the body, allowing it to shrink and potentially eliminate tumors.

While chemo can be life-saving, there is one downfall of its cancer-fighting method: Cancer cells aren’t the only cells that divide quickly. Chemo drugs can’t tell the difference between healthy cells and cancer cells, so it knocks down some healthy cells as well.

This can cause many unpleasant side effects, such as:

  • Fatigue

  • Hair loss

  • Easy bruising/bleeding

  • Infections

  • Anemia

  • Nausea and vomiting

  • Mouth sores

  • Low appetite

  • Constipation and diarrhea

  • Nerve and muscle problems

  • Skin and nail changes

  • Bladder changes

  • Weight changes

  • “Chemo brain”

  • Mood changes

  • Libido changes

  • And fertility problems.

When doctors administer chemo, they aim to find a balance between killing the cancer cells (in order to cure or control the disease) and sparing the normal cells (to lessen side effects).

Although newer treatment types for cancer (namely immunotherapy and targeted therapy) do not create as many side effects, these therapies do not work against all cancer types.

Chemo may not be perfect, but there’s no denying how helpful it’s been in fighting such a difficult disease.