Knowledge of the long-term impact of cancer immunotherapies on the body is still incomplete. Nevertheless, immunotherapy is increasingly becoming the standard of care for many types of cancer—melanoma, non–small cell lung cancer, and bladder cancer, for example—meaning that the number of patients exposed to these treatments is growing, as is the chance of developing toxicities from these drugs.^[1]

Commonly regarded as “kinder” on the body than chemotherapy, immunotherapy drugs still have side effects and toxicities. Awareness about the specific toxicities of immunotherapy drugs is crucial. Physicians and patients alike need to understand and manage the side effects of these treatments.

The European Society for Medical Oncology (ESMO) recently published clinical practice guidelines on the management of toxicities from immunotherapy^[2]and has just launched a patient guide on the management of immunotherapy side effects.^[3] It contains information on how immunotherapy works, the most common toxicities associated with checkpoint inhibitors, how the oncology team can manage these symptoms, and a few strategies that patients can use to minimize side effects. ESMO’s guide provides this information in clear and easy-to-understand language, including helpful illustrations, tables, and a glossary so that patients and caregivers can identify potential side effects.

Chemotherapy Versus Immunotherapy: ‘What’s the Difference?’

Unlike chemotherapy, which “kills” cancer cells by damaging them so that they cannot reproduce and spread, immune checkpoint inhibitors, a type of immunotherapy, work differently, by enhancing the body’s own immune response. T cells, a type of white blood cell, are immune cells that turn the immune response on or off, which is typically used to protect us from disease—by killing viruses, for example. However, some cancer cells make proteins that turn off T cells so that they don’t attack cancer. Checkpoint inhibitors target and activate T cells, enabling them to recognize, attack, and destroy cancer cells.

Because immunotherapy with checkpoint inhibitors blocks the body’s natural safeguards that prevent immune overactivation, it can also affect healthy cells and normal tissues and cause autoimmune side effects. These are different from those associated with chemotherapy and tumor-targeting drugs, and require different management strategies.

Common Side Effects and Toxicities for Immunotherapies

Checkpoint inhibitors are among the most promising treatments for cancer, but like any other medicine, they are associated with toxicities. Because immune checkpoint molecules play an important role in maintaining the balance between an effective immune response and autoimmune disease, blocking them may lead to severe autoimmune reactions such as diarrhea or hepatitis, or milder reactions such as rashes or thyroid gland disorders.

Depending on the immune checkpoint that is targeted, the type and severity of toxicities vary. Most frequently, they affect the skin, colon, endocrine organs, liver, and lungs. Others are infrequent but may be very serious—even lethal—such as neurologic disorders and myocarditis.

The ESMO Clinical Practice Guidelines on the Management of Toxicities from Immunotherapy contain lists of immuno-oncology drugs approved in Europe and the United States and provide an overview of the main immune-related adverse events, including the grading of symptoms and recommendations for their management.