Understanding immunotherapy in small cell lung cancer

If you or a loved one has been diagnosed with extensive-stage small cell lung cancer (SCLC), you may hear about immunotherapy as part of your treatment plan. While chemotherapy has “been in place since the 1990s,” according to Memorial Sloan Kettering Cancer Center’s Dr. Charles Rudin, immunotherapy is changing what longer-term outcomes can look like for some patients. 

Here’s what experts want you to know about when it’s used, who it’s for, and what side effects to watch for.

How immunotherapy fits into SCLC treatment

SCLC is known to be highly responsive to chemotherapy. Dr. Rudin explains, “This disease is very chemotherapy responsive. We see pretty dramatic shrinkage of tumors with chemotherapy.”

Today, the standard first-line approach for extensive-stage SCLC typically combines chemotherapy with immunotherapy. Where immunotherapy becomes especially important is over time. After the initial treatment period, patients often continue on maintenance immunotherapy alone.

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Before immunotherapy was part of treatment, outcomes tended to decline quickly after chemotherapy stopped. Now, doctors are seeing a different pattern. Dr. Rudin says, “There’s a tail on that curve, meaning there are patients who are long-term survivors.” For patients who remain free of disease progression months later, he adds, “That’s where immunotherapy is clearly benefiting them, because historically, they would not have made it.”

Who is immunotherapy for?

For most people with SCLC, immunotherapy is considered a standard part of care. Dr. Rudin emphasizes that “the large majority of patients with small cell lung cancer are eligible to get immunotherapy, and frankly, should get immunotherapy, if at all possible.”

However, there are some exceptions. Immunotherapy may not be appropriate for people with significant autoimmune conditions, such as lupus, because it can worsen an already overactive immune system. 

Even with these considerations, experts continue to recommend immunotherapy broadly. Massachusetts General Hospital’s Dr. Catherine Meador shares, “There’s a small percentage of patients that are actually benefiting [from immunotherapy] more than the rest.” She adds, “We don’t understand that enough scientifically or biologically to remove immunotherapy from any patient, because there’s been just enough of a signal that for all patients, we should treat them with immunotherapy.”

Understanding immunotherapy side effects

Immunotherapy has its own set of side effects. Since immunotherapy activates the immune system, side effects often happen when the immune system starts attacking healthy tissues. “We’re actually taking the brakes off the immune system,” Dr. Rudin explains, “so the immune system is active not only against the cancer, but it can become active against normal tissues of the body.”

Some of the more common or notable side effects include:

• Colitis, which can cause diarrhea
• Thyroid problems, including loss of thyroid function
• Skin reactions, like rashes (dermatitis)
• Other inflammatory conditions throughout the body

In rare but serious cases, patients may develop pneumonitis, or inflammation in the lungs. “That can actually be fatal,” Dr. Rudin notes, which is why treatment is stopped immediately if it occurs.

Managing side effects

Many immunotherapy side effects can be managed and even reversed if caught early. Dr. Rudin shares, “Many [side effects] are treatable, so if we stop therapy and give a course of steroids, we sort of cool down the immune system. We can often reverse some of these autoimmune side effects, and even in some patients, resume immunotherapy.”

What if immunotherapy needs to be stopped?

If side effects become severe, some patients may need to stop immunotherapy. Even then, Dr. Rudin acknowledges there may still be a benefit if the treatment is discontinued because “they may still have had the benefit of activating the immune system.”

Looking ahead

New research is looking to understand why some patients respond better to immunotherapy than others. Dr. Meador also adds, “I think there will be more data coming. Other types of immunotherapies that were approved in the second-line layers are now being tested in multiple first-line settings, suggesting maybe it makes sense to look at [including immunotherapy] earlier, but we’ll have to see what the FDA says.”

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