That makes you vulnerable to illness and infection.
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How Does Cancer Treatment Affect the Immune System?
Chemotherapy (chemo) and radiation therapy (also called radiotherapy) kill cancer cells.
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The problem is, they also kill rapidly dividing healthy cells.
Each treatment has its own effects.
Chemotherapy
Chemotherapy is a systemic treatment, meaning it affects your whole body.
Many types of chemo are given as injections or infusions.
It can also be given by mouth, in pill form.
Cancer cells grow and divide quickly.
Chemo is designed to go after fast-growing cells like cancer.
However, it cant tell one fast-growing cell from another.
That means it kills many types of cells in your body.
One of their jobs is to produce white blood cells for the immune system.
White blood cells are responsible for attacking and killing viruses, bacteria, and other pathogens.
The most common chemo-related problem isneutropenia.
This is a decrease inneutrophils(white blood cells), which are important for immunity.
Recap
Chemotherapy kills fast-growing cells, including cancer and bone marrow cells.
Damage to bone marrow means it can’t produce disease-fighting immune-system cells.
Low white blood cell counts (neutropenia) can result.
Radiation
Radiation works differently than chemo.
This means cells either die or become unable to divide, which is how cells reproduce.
This shrinks tumors or slows their growth.
That’s because radiation isn’t systemic.
Rather, it is targeted right at your tumor.
Metastatic Disease
When cancer spreads, called metastasis ormetastatic disease, the whole body may need radiation.
It may also cause other conditions that harm the immune system.
For example, radiation near the underarm can damagelymph nodes, which are part of the immune system.
The damage can lead to an increased risk of infection in the arm.
Radiation can deal a lot of damage when its aimed at bones.
The effect on bone marrow is similar to that of chemo.
Radiation damages cellular DNA.
This kills cancer but can impair immune-system cells.
Effects are usually milder than with chemo but are also less predictable.
Immune system damage may be direct or resulting from complications of radiation.
How Strong Is Your Immune System After Cancer Treatment?
After chemo and radiation, your immune system can stay suppressed for several months.
Several types of immune-system cells were depleted.
In people who smoked, some immune cells were only at 50% of normal levels after nine months.
Thats compared to an 80% rate in nonsmokers.
Researchers say the immune-system damage could leave you vulnerable to some illnesses even if youve been vaccinated.
Specific chemo drugs have different effects.
Those who took anthracycline plustaxane,a more traditional chemo drug, recovered much more slowly.
It can take months for the immune system to rebound after chemo and radiation.
The specific drug(s) can make a difference in recovery time.
Smokers tend to recover more slowly.
This will help them understand the seriousness of the situation.
Lasting Side Effect
Healthy cells damaged by chemotherapy generally heal well once treatment ends.
An exception is nerve cells in your hands and feet.
They can have permanent damage that leads to a painful condition calledperipheral neuropathy.
Summary
Chemotherapy kills fast-growing cells, which includes many healthy cells, along with cancer cells.
Bone marrow cells are frequently damaged and unable to produce white blood cells.
This hampers your immune system.
Radiation damages the genetic material of cells.
This kills both cancer and immune-system cells.
Effects tend to be less than with chemo.
Radiation may directly damage the immune system or may cause other conditions that impair your immunity.
Much of this depends on where the cancer is.
Your immune system may take months to rebound after chemo and radiation.
Be sure to take steps to protect yourself from infection.
If you notice symptoms of infection, get medical attention right away.
A Word From Verywell
More people are surviving and thriving after cancer all the time.
Once you beat the disease, though, you cant let up your guard.
Impaired immunity can pose a real threat.
Just being aware of the problem is a start.
Frequently Asked Questions
No, effects aren’t permanent.
It takes time, but the immune system does recover.
The amount of time that takes varies by treatment jot down, duration, and other factors.
One study found normal or near-normal immune function within nine months of ending chemo.
Research suggests cancer and its treatments may shorten life expectancy by 30%.
Most people recover a large amount of immune function within nine months of chemo.
It may take longer for smokers.
Radiation’s effects are less predictable.
American Cancer Society.Why are people with cancer more likely to get infections?
Cancer Treatment Centers of America.How do cancer treatments damage the immune system?
National Institutes of Health, National Cancer Institute.Radiation therapy to treat cancer.
BreastCancer.org.How radiation therapy affects the immune system.
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Published 2016 Jan 26. doi:10.1186/s13058-015-0669-x
Centers for Disease Control and Prevention.Know the signs and symptoms of infection.
BreastCancer.org.How chemotherapy affects the immune system.
Cupit-Link MC, Kirkland JL, Ness KK, et al.Biology of premature ageing in survivors of cancer.ESMO Open.
2017;2(5):e000250.
Published 2017 Dec 18. doi:10.1136/esmoopen-2017-000250
