How Does Chemotherapy Work?

Chemotherapy is a cancer treatment that uses drugs or a combination of drugs to treat cancer.

Chemotherapy works by stopping or slowing the growth of cancer cells, which grow and divide quickly, by damaging the part of the cell that makes it divide. It is considered a systemic therapy because the chemotherapy process treats the whole body to kill any cancer that may be spread throughout the body or to kill any microscopic or small cells that could be separate from the origin of the cancer.

With cancer, cells keep dividing rapidly until there is a mass of them. This mass of cells is a tumor. Since cancer cells divide at a higher rate than most normal cells; chemotherapy targets these rapidly dividing cells causing a tumor to stop growing and even dying.


The most common side effect is fatigue. Chemotherapy not only kills fast-growing cancer cells, but also affects the growth of healthy cells that grow and divide quickly. An example are the cells that cause your hair to grow. Damage to healthy cells may cause side effects, such as nausea, and hair loss. Side effects often get better or go away after you have finished chemotherapy.

Chemotherapy may be given in many ways, and our cancer specialist will guide you through your cancer treatment. Some common ways include:

  • Oral: The chemotherapy comes in pills, capsules, or liquids that you swallow.
  • Intravenous (IV): The chemotherapy goes directly into a vein. This is the most common form of chemotherapy treatment, and IV chemotherapy may also be given through catheters or ports, sometimes with the help of a pump to avoid repeated needle sticks into the patient.
  • Injection: The chemotherapy is given by a shot in a muscle in your arm, thigh, or hip, or right under the skin in the fatty part of your arm, leg, or belly.
  • Intrathecal: The chemotherapy is injected into the space between the layers of tissue that cover the brain and spinal cord.
  • Intraperitoneal (IP): The chemotherapy goes directly into the peritoneal cavity, which is the area in your body that contains organs such as your intestines, stomach, and liver.
  • Intra-arterial (IA): The chemotherapy is injected directly into the artery that leads to the cancer.
  • Topical: The chemotherapy comes in a cream that you rub onto your skin. THis is most often used for skin cancer.