Side Effects

Immunotherapy boosts the body’s immune system, and it typically results in fewer side effects that can be less severe than those associated with other forms of cancer treatment. However, not everyone experiences the same side effects, and, for some people, they may become more severe. Side effects of any cancer treatment can be physical as well as emotional, and some can be prevented while others may be managed. Knowing what to expect, and what to do if side effects do occur, will make your treatment experience more manageable. If you feel better, you are more likely to finish your treatment as planned by your treatment team. Ask your medical team about the side effects you can expect with immunotherapy, and when they are likely to occur.

Following are some side effects associated with immunotherapy.

Immune-mediated Adverse Reactions

Immune-mediated adverse reactions are not common but can occur and tend to be the most serious of the possible side effects. This type of reaction occurs when the immune system is overstimulated by the treatment and may cause inflammation, swelling or redness, which may be painful. Following are some of the systems affected by immune-mediated adverse reactions and common symptoms:

  • Endocrine (endocrinopathies): hyperthyroidism, hypothyroidism, extreme fatigue, persistent or unusual headaches
  • Gastrointestinal (colitis): diarrhea with or without bleeding, abdominal pain, bowel perforation
  • Neurologic (neuropathies): numbness or tingling, sensory overload or sensory deprivation
  • Pulmonary (pneumonitis): chest pain, shortness of breath
  • Renal (kidneys) (nephritis): Decrease in urine output, blood in urine, swelling in ankles, loss of appetite
  • Skin (dermatitis): Rash, skin changes

Since immunotherapy works differently than other cancer treatments, partnering with your doctor to monitor for complications is vital. To determine what is normal for you, your doctor likely will perform baseline assessments for monitoring purposes throughout treatment. You will play a key role in noticing what is abnormal for you and communicating that to your doctor immediately. It is important to understand how to recognize an immune-mediated adverse reaction, as some may not produce obvious symptoms.

Having the appropriate contact information handy is important. Before beginning immunotherapy, ask your health care team whom to call, day or night, if you think you may be having an immune-mediated adverse reaction. It is necessary to call that person immediately to avoid any life-threatening complications. Without treatment, an autoimmune response can be irreversible or even deadly. For the majority of reactions, early intervention can be reversed with steroids and by temporarily stopping immunotherapy.

These types of side effects can happen, sometimes occurring weeks or even months after treatment stops. Work with your doctor to determine a plan for how long to be vigilant about potential side effect symptoms.


Fatigue is the most common side effect reported in multiple immunotherapies, including checkpoint inhibitors, cytokines and oncolytic virus therapy. Fatigue associated with cancer is different than simply feeling tired and may cause you to feel physically, emotionally or mentally exhausted.

Flu-like Symptoms

Flu-like symptoms, such as fever, chills, aches, headache, drowsiness, nausea, vomiting, loss of appetite and low or high blood pressure, can occur with cytokines or oncolytic virus therapy.


Diarrhea is common with checkpoint inhibitors and can vary in severity and duration. Diarrhea can lead to severe dehydration and electrolyte imbalance, but also could be a symptom that your immune system is going into overdrive. Call your health care team if you experience symptoms that interfere with your daily activities, such as severe abdominal cramping or episodes that make you fearful of leaving your home.

Mild Skin Reactions

Mild skin reactions, such as bumpy or itchy red rashes, can occur. These reactions can be common with checkpoint inhibitors. Other skin problems include yellowing or changes in skin color, inflammation, blistering, hives, pale patches, dryness, cracking of the fingertips, sun sensitivity, and flushing or redness. Although rarely severe, these symptoms can be uncomfortable. Your doctor may recommend a corticosteroid or numbing medicine, antihistamine, medicated creams or antibiotics.


Depression can affect your mood, behavior and ability to think and concentrate, as well as be associated with fatigue, appetite loss, difficulty falling asleep or extreme tiredness. Depression can include suicidal thoughts or other psychiatric disorders. Call your doctor’s office if you notice these types of mood changes.

Mouth Sores

Mouth sores are small cuts or ulcers that can affect the gums, tongue, roof of the mouth or lips. Mouth sores sometimes begin as mild pain or burning, followed by white patches that may become large red lesions. Pain may range from mild to severe, making it difficult to talk, eat or swallow. Mouth sores are more easily managed when caught early. Talk to your doctor if you have symptoms.

Swelling of the Legs

Swelling of the legs (edema) is caused by fluid accumulation in the body’s tissues. The effects of edema may be reversed. Talk to your doctor if you notice swelling, stiffness, recent weight gain, puffiness or a heavy feeling in your legs.

Heart Palpitations

Heart palpitations may occur as a side effect of some immunotherapy treatments. If you notice an abnormal heart rhythm or feel dizzy or light-headed, contact your doctor immediately.


Because immunotherapy drugs work by altering the way that the immune system works, it is possible that the effect may cause the immune system to attack normal, healthy parts of the body, such as the intestines, liver, lungs, kidneys, hormone-making glands or others. Frequent communication with your health care team is important for monitoring your symptoms. Seek treatment immediately, regardless of time of day, for any medical emergencies, including high fever, inflammation, swelling, severe abdominal pain or shortness of breath.

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