How Is Immunotherapy Different from Chemotherapy?

One of the biggest misconceptions oncologist Melissa Wilson hears from patients about immunotherapy for cancer treatment has to do with the side effects. They think immunotherapy’s side effects will be similar to those from chemotherapy, one of the most commonly used cancer treatments. But they’re mistaken.

The reason has to do with how immunotherapy drugs and chemotherapy drugs work in the body to attack and destroy cancer cells.

Immunotherapy is actually an umbrella term for a variety of treatments that aid the body’s immune system in fighting off cancer cells. (Learn more about the types of immunotherapy treatments here.) This FDA-approved cancer treatment has improved outcomes for various types of cancers and can be used after chemotherapy has failed or in conjunction with chemotherapy.

In comparison, chemotherapy attacks rapidly dividing cells indiscriminately, according to Dr. Wilson, MD, PhD, of the NYU Langone Medical Center in New York City. Rapid growth and division is a defining quality of cancer cells, so chemotherapy attempts to eliminate tumors by targeting any cells growing quickly.

Unfortunately, some normal and healthy cells, like those in your digestive tract, also divide rapidly, so chemotherapy targets these cells as well. This causes chemotherapy’s well-known side effects, such as hair loss, mouth sores, nausea, vomiting, diarrhea, constipation, and decreased blood counts. These side effects are a direct result of chemotherapy attacking healthy cells while targeting rapidly dividing cancer cells.

Immunotherapy, on the other hand, revs up the body’s natural immune system. Cancer cells find ways to masquerade as healthy cells, preventing the T cells of the immune system from recognizing them as foreign. Because the T cells do not notice the harmful cells, they do not target them, which allows the tumor to continue growing and spreading throughout the body.

With FDA-approved immunotherapy treatment, the activated T cells are better able to discriminate between cancer cells and healthy cells, and they can then shrink or kill off the cancer cells more effectively. Not only does this mean immunotherapy is more effective at recognizing and eliminating cancer cells, but it is also less likely to kill off healthy cells that are crucial to the overall well-being of the patient.

This does not mean immunotherapy is free of side effects, however. Side effects of immunotherapy stem from the way it revs up your immune system. These include rashes, diarrhea, liver inflammation, and hypothyroidism. Thankfully, doctors have ways to treat these side effects of immunotherapy and are prepared to counsel and support patients through the process.