What Are Common Side Effects of Immunotherapy?

By: David Grew MD MPH

"Immunotherapy side effects can be different because they may come from the immune system attacking healthy tissue.."

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Immunotherapy is a type of cancer treatment that helps the body’s immune system find and fight cancer. One common kind is called an immune checkpoint inhibitor. These medicines can be very effective for some cancers, but they can also cause side effects that look different from the side effects people may expect from chemotherapy.

A big reason is that immunotherapy can make the immune system more active. Sometimes that helps it attack cancer. But sometimes it can also cause the immune system to attack healthy parts of the body, leading to inflammation in different organs.

Common side effects patients may notice

Some of the more common side effects reported with immunotherapy include:

• fatigue
• rash or itching
• diarrhea
• nausea
• cough
• loss of appetite
• joint or muscle aches
• fever or chills in some settings

Not every patient has the same experience. Some people have only mild symptoms, while others may develop more serious problems that need prompt treatment.

Why immunotherapy side effects can be different

Unlike some other cancer treatments, immunotherapy side effects are often related to inflammation caused by an overactive immune system. This means side effects can affect many different organs, including the:

• skin
• intestines
• lungs
• liver
• thyroid and other hormone-producing glands
• joints and muscles
• kidneys
• heart
• eyes
• nervous system

That is one reason doctors often tell patients to report new symptoms early, even if they seem minor at first. Early treatment can matter.

Skin side effects

Skin changes are among the most common side effects of checkpoint inhibitors. Patients may notice:

• rash
• itching
• dry skin
• skin color changes in some cases

These problems are often manageable, but patients should still tell their care team if a rash is spreading, painful, or interfering with daily life.

Digestive side effects

Immunotherapy can affect the digestive system. Patients may develop:

• diarrhea
• nausea
• belly pain
• inflammation of the colon in more serious cases 

Diarrhea is especially important to report, because it can sometimes be a sign of a more serious immune-related side effect rather than just a routine upset stomach. 

Lung side effects

A less common but important side effect is pneumonitis, which means inflammation in the lungs. Symptoms can include:

• shortness of breath
• cough
• chest discomfort in some cases

Because breathing symptoms can become serious, patients should contact their care team right away if they develop new or worsening shortness of breath or cough during immunotherapy. 

Hormone and gland side effects

Immunotherapy can also affect glands that make hormones, especially the thyroid. Some patients may develop thyroid inflammation or low thyroid hormone levels. This can lead to symptoms such as:

• fatigue
• feeling cold
• constipation
• weight changes
• dry skin

These problems may be harder to notice because they can look like general treatment fatigue, which is why blood tests and regular follow-up matter. 

Rare but serious side effects

Most patients do not develop severe side effects, but serious immune-related problems can happen. Public patient resources from NCI and NCCN note that immunotherapy can sometimes affect organs such as the lungs, liver, kidneys, heart, eyes, or nervous system.

These side effects may need steroids, treatment delays, or stopping immunotherapy altogether, depending on how severe they are. 

When should patients call their care team?

Patients should let their oncology team know promptly about new or worsening symptoms during immunotherapy, especially:

• diarrhea that is more than mild
• new rash
• worsening fatigue
• cough or shortness of breath
• fever
• severe belly pain
• dizziness
• new weakness
• vision changes
• any symptom that feels unusual or rapidly worse

It is better to ask early than wait and hope a symptom goes away. With immunotherapy, early recognition is an important part of staying safe. 

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Immunotherapy can be an important part of cancer treatment, and many side effects are manageable. But its side effects can be different from what patients expect because they may come from the immune system attacking healthy tissue as well as cancer. 

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To learn more about immunotherapy for cancer, watch this video we created to explain the topic.

To learn more, browse our library of general cancer-related topics.

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FAQs:

Can immunotherapy side effects start a while after treatment begins, instead of right away?
Yes. NCCN’s patient resource notes that side effects from checkpoint inhibitor immunotherapy can happen days, weeks, or even months after treatment starts, and some can happen after treatment stops. That is one reason patients should keep reporting new symptoms to their care team, even if the timing seems unexpected.

Are immunotherapy side effects always worse than chemotherapy side effects?
No. They are often different, not necessarily worse across the board. NCI explains that immunotherapy side effects can look different because they may come from immune-related inflammation rather than the more familiar side effects patients may associate with chemotherapy. Patients should ask their care team what side effects are most likely with their specific treatment.

Can immunotherapy cause hormone problems like thyroid issues?
Yes. NCI reports that thyroid inflammation and low thyroid hormone levels can happen with immune checkpoint inhibitors. Sometimes these symptoms are easy to miss because they can look like fatigue or general illness, so patients should tell their care team about changes in energy, weight, bowel habits, or temperature sensitivity.

Should I call my care team for mild diarrhea or a mild rash?
Yes. Public patient guidance from NCCN emphasizes reporting symptoms when they start because early recognition can help find the cause and trigger treatment sooner if needed. Even symptoms that seem minor at first can become more important in the setting of immunotherapy.

Can immunotherapy side effects usually be treated?
Yes, often they can. NCCN notes that many immune-related side effects are manageable, but treatment depends on the organ involved and how severe the problem is. Some patients may need close monitoring, medicines such as steroids, or a pause in immunotherapy. Patients should contact their care team promptly if symptoms are getting worse.