Immunotherapy Side Effects: When to Call

This page is for people getting immunotherapy and the people who care for them. It covers which side effects to watch for and when to call.

Immunotherapy helps your immune system act against cancer. It can also trigger inflammation in normal, healthy tissue. You do not need to memorize every possible side effect. What matters most is having a clear plan for which symptoms your team wants to hear about right away, and which need emergency care.

Many cancer treatments mainly damage fast-growing cells. That is why hair loss and mouth sores are common with chemotherapy. Immunotherapy side effects work differently. Your activated immune system can start affecting a healthy organ, not just the cancer. That organ can be your skin, lungs, colon, liver, hormone glands, kidneys, nerves, or another part of the body. Doctors call these immune-related adverse events.

Immunotherapy side effects can start at almost any point. The National Cancer Institute notes they can occur during treatment or after it has ended. A new symptom weeks or months after your last dose can still be related to immunotherapy. Read new symptoms with your treatment history in mind, not just how you feel today.

NCI sets these out organ by organ.

• Digestive system. Colitis brings stomach or belly pain, diarrhea, and black, tarry or bloody stools. Black or tarry stool is an emergency. Some people have mild hepatitis, picked up only on a blood test.
• Hormone glands. Inflammation of the pituitary gland can cause headaches and fatigue. Adrenal inflammation causes fatigue, muscle weakness, appetite loss, weight loss and belly pain. An underactive thyroid brings weakness, constipation, dry skin, weight gain and feeling cold; an overactive one brings diarrhea, weight loss, sweating and heat sensitivity.
• Pancreas. Severe belly pain with nausea and vomiting.
• Lungs. Pneumonitis makes you short of breath and gives you a bad cough.
• Skin. Rashes, itching, blisters and sores.
• Liver. Hepatitis yellows the skin and eyes, and can bring dark urine, nausea, stomach pain and easy bleeding.
• Kidneys. Nephritis can cut how much urine you make, or put blood in it.
• Heart, eyes and nerves. Heart inflammation, called myocarditis, can lower your blood pressure and, in rare cases, weaken the heart's pumping, disrupt your heartbeat, or cause a heart attack. MedlinePlus lists chest pain, shortness of breath, a fast heartbeat, fainting and leg swelling among the symptoms of myocarditis. Uveitis or episcleritis can change vision or cause eye pain. Nerve inflammation causes tingling, numbness or weakness in the hands, feet and sometimes the face.

NCI notes that your doctor will check your hormone levels regularly to find these gland problems.

Some symptoms need contact with your team right away, not a wait for your next visit. Do not wait for a stool count or for the symptom to get worse first. These include new or worsening diarrhea, blood or mucus in your stool, a new cough or breathlessness, a widespread or blistering rash, yellowing skin or eyes, eye pain or blurred vision, passing much less urine than usual, and new tiredness, weakness, fast heartbeat, feeling cold, or a change in weight or sweating (possible hormone gland problems). Use the 24-hour number your team gave you, and follow the emergency instructions on your treatment card. MedlinePlus says to contact your doctor immediately about these with pembrolizumab.

A few symptoms mean you should call 911 or go to the nearest emergency department straight away, rather than phoning your team first. Black, tarry or sticky stools, heavy bleeding, and sudden confusion belong here too. Severe shortness of breath, chest pain or pressure, a racing or irregular heartbeat with dizziness, fainting, and signs of a severe allergic reaction such as swelling of the face or throat all belong in that group. So does the picture NCI describes for encephalitis, inflammation of the brain: a sudden high fever with confusion, hallucinations, seizures or vomiting. Do not drive yourself.

NCI is explicit that this split is personal. Your oncologist may want to be called first about inflammatory symptoms, or may tell you to go straight to emergency care. Ask which, and write the answer down. For the emergency signs above, do not wait for a call back: call 911.

NCI names three things to write down and keep handy: the drug name or names, your doctor's contact information, and your hospital's contact information. That note is for the emergency room, where nobody knows your treatment history.

Ask your team for a written list to go with it. It should cover which symptoms need a call right away, the number to use after hours, and what to tell urgent-care clinicians about your immunotherapy. Immune-related inflammation is managed differently from an ordinary infection, often with steroids that calm the immune response, so the clinician treating you needs to know what you are on.

Do not assume a new symptom is harmless just because it seems unrelated to your cancer. Do not assume every new symptom is immune-related either. Infections and medicine side effects still happen during immunotherapy. Sorting this out is your care team's job. Reporting the symptom promptly is yours.

How a side effect is managed depends on which organ is involved and how severe it is. Your team weighs the benefit of continuing immunotherapy against the risk of the side effect. This is part of why prompt reporting matters: catching a problem early, while it is mild, generally gives your team more ways to manage it well.

• Which symptoms should I report right away?
• Which symptoms should lead to urgent or emergency care if I cannot reach you?
• Do I need to carry an immunotherapy wallet card or medication list?
• If I develop a side effect, what does treatment for it usually involve, and would it change my immunotherapy schedule?

• National Cancer Institute — Immunotherapy Side Effects
• National Cancer Institute — Organ-Related Inflammation and Immunotherapy
• MedlinePlus — Myocarditis
• MedlinePlus — Chest pain