How Is Immunotherapy Different from Chemotherapy?
These two cancer treatments work very differently to destroy cancer cells and have very different side effects.
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.
Dr. Wilson is an assistant professor of medicine at NYU Langone’s Perlmutter Cancer Center, focusing on melanoma.
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There are a number of different
ways that we can treat cancer.
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I think one of the most
confusing things for
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patients is this realization
that immunotherapy isn't
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like standard treatment like
they've received in the past.
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So a lot of patients feel
that immunotherapy is
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very similar to chemotherapy.
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But chemotherapy actually attacks
rapidly dividing cells indiscriminately.
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So It's not specific for
a tumor cell versus a non-tumor cell.
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It really does attack
rapidly developing cells.
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And so this is actually why patients
develop some of the side effects they do
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with chemotherapy because we see rapidly
dividing cells in the body be affected.
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So hair loss, problems with GI tract,
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so some mouth sores, nausea,
vomiting, diarrhea, constipation,
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as well as decrease in blood counts
because the blood cells get affected.
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With immunotherapy, we're actually
revving up the body's immune system.
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Meaning, we've revved up the body's T
cells that are fighting the cancer cells,
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but sometimes they get confused on those
T cells then attack other normal organs,
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normal systems.
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So you can get a rash or
itchiness, you can have them,
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have attacks in the colon, so
you can get a diarrhea with that.
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They attack the liver.
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You get inflammation in the liver, and
you can have abnormal liver numbers or
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an immune hepatitis.
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We also have issues with the thyroid gland
where it attacks the thyroid gland and
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causes hypothyroidism.
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So immunotherapy certainly has a lot of
side effects that we counsel patients on,
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and it certainly sounds really
scary to patients when we tell
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them about everything and anything
that could possibly happen to them.
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And it's pretty overwhelming at times.
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But one of the things that
we really do try to stress
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to the patient is that we're here
to help them through all of it.
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And while it sounds scary,
we have ways to treat the side effects.
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And so that they really should feel
comfortable talking to us about
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everything that's going on so
that we can help them.
Immunotherapy by cancer type. New York, NY: Cancer Research Institute. (Accessed on June 29, 2017 at https://www.cancerresearch.org/we-are-cri/home/cancer-types.)
What are the side effects of immunotherapy? Boston, MA: Dana-Farber Cancer Institute, 2017. (Accessed on July 6, 2017 at http://blog.dana-farber.org/insight/2016/02/what-are-the-side-effects-of-immunotherapy/.)
What is cancer immunotherapy? Atlanta, GA: American Cancer Society, 2016. (Accessed on June 29, 2017 at https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/immunotherapy/what-is-immunotherapy.html.)