Extending Life But With Possibly Serious Side Effects
- Checkpoint inhibitors trigger the immune system to attack cancer cells.
- The body’s natural immune response involves inflammation.
- Major inflammation can cause minor or severe side effects from rash to organ damage.
View this post on InstagramRead More In the photo's caption, the reality TV star writes, "I don't understand how medicines that hurt u can help u." So, let's explain why that happens.Immunotherapy drugs called checkpoint inhibitors have dramatically improved prognoses for people facing many different types of metastatic cancers, including lung cancer, melanoma and colon cancer. They have given years of life to people who otherwise would have had no other options. But it's true that they can cause painful, and sometimes serious, side effects.
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"The risks of immune therapy depend a little on the drug, but often cause rashes," Heather Yeo, MD, tells SurvivorNet. "They can affect the GI tract, endocrine organs, the liver, lungs, and the kidneys. Often they are mild, but can be life threatening." Yeo is a surgical oncologist who treats colorectal cancers at Weill Cornell Medicine.
Skin rashes, like Anderson's, as well as hypothyroidism are among the most common side effects of checkpoint inhibitors.
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"But they are often relatively easy to manage [with medications]," Sandip Patel, MD, tells SurvivorNet. More serious adverse events, he adds, include inflammation of the lungs, colon or heart. "These are quite rare and depend on the specific regimen, but in general severe versions of these toxicities occur in less than one in 25 patients. But, they can be life-threatening, so early diagnosis and intervention with steroids are key." Patel is a medical oncologist at UC San Diego Health with expertise in immunotherapy for lung cancer.
Checkpoint inhibitors work by prompting your own immune system to attack cancer cells. But once the system is revved up, it can cause all kinds of immune-related side effects, too. Here's how your immune system works, how these drugs fight cancer, and why they can cause painful side effects, too.
How the Immune System Works
Your immune system's job is to recognize threats, such as infections and other illnesses, when they enter the body and fight them off. Immune cells fight off illness with inflammation, and you feel the effects of that inflammation the form of fever, rash, swelling, diarrhea and other signs of an immune response in action.
Lucky for you, the immune system has controls in place to make sure it doesn't launch a full-throttle attack on every unknown piece of dust that enters your body or worse, an attack on you. If not for these controls, everyone would get random fevers, rashes and diarrhea all the time.
That's why immune cells have receptors on them that match up with proteins on other healthy cells. When an immune cell encounters a cell with one of these matching proteins, the immune system allows the cell to pass through this so-called checkpoint unhindered. It's as if the cells have a secret handshake or password. If an unfamiliar cell does not bear one of these proteins, the immune cells know to attack it.
How Cancer Tricks the Immune System
Cancer cells know how to outsmart immune checkpoints. They often carry proteins on their surface that match up with receptors on immune cells. That allows them to sneak through these checkpoints and grow, multiply, and spread throughout the body without any interference.
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Immunotherapy drugs called checkpoint inhibitors disable this system. Some block the receptors on your immune cells; others block the matching proteins on cancer cells. Either way, the drugs make immune cells able to recognize cancer cells for what they are: an unwelcome invader and a threat.
How Drugs that Hurt You Can Help You
You might imagine that when these safeguards on the immune system have been disabled, your immune cells can unleash a pretty fierce attack. So, while it kills cancer cells, that mighty immune response can cause all sorts of inflammation, too. Sometimes it leads to a rash like the one on Anderson's back. In rarer cases, it can lead to inflammation of vital organs, including the lungs and heart.
But, the powerful drugs are life-giving as well.
"For people who are not candidates for targeted therapy, immunotherapy has been our most important advance in lung cancer," Patel says. "Efforts to develop new immunotherapies to help those patients that don't respond to the current FDA-approved ones is key in unlocking the promise of cancer immunotherapy for all our patients fighting this disease."
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