Small cell lung cancer (SCLC) is one of the two major categories of lung cancer along with non-small cell lung cancer (NSCLC).

SCLC makes up about 13 to 15 percent of all lung cancers. Smoking is thought to cause 85 percent of lung cancers and is strongly associated with SCLC.

Chemotherapy and radiation therapy are the most commonly used methods to treat SCLC.

But immunotherapy is a relatively new and promising treatment for SCLC and other cancers. It may also be combined with chemotherapy or radiation therapy as an initial treatment or used later if other therapies aren’t effective.

Read on to learn how immunotherapy works for treating SCLC and what the latest research says.

Immunotherapy involves taking medications that stimulate your immune system to identify and destroy cancer cells. Three primary classes of immunotherapy drugs are used to treat SCLC.

Immune checkpoint inhibitors

Your immune system undergoes a process called cancer immune surveillance. This means that your immune system searches for proteins called antigens produced by cancer cells. When it finds these antigens, your immune system targets the cancer cell and destroys it.

Your immune system uses certain proteins called checkpoints to turn your immune response on and off. These checkpoints help prevent your immune system from being too aggressive. But if checkpoints are overactive, they can prevent your immune system from identifying and targeting cancer cells.

Some tumors can go undetected by your immune system when these checkpoints are overactive, interfering with your T cells and natural killer cells’ ability to recognize cancer cells.

A class of immunotherapy drugs called immune checkpoint inhibitors block these checkpoints so your body can better recognize and kill cancer cells.

Tumor vaccines

Tumor vaccines are different from vaccines that target viruses. These vaccines bind to antigens produced in tumor cells, alerting your immune system to attack the cancer cells.

Monoclonal antibodies

Monoclonal antibodies are proteins made in a lab that act like your immune system’s antibodies. Antibodies are proteins produced by your immune system that bind to antigens attached to foreign substances in the body. This give your immune system the signal to attack them.

Cancer researchers can now design antibodies that target certain antigens found on cancer cells. This can help stimulate your immune system to kill cancer cells.

Chemotherapy and radiation therapy are the primary treatments for SCLC. But researchers are hopeful that immunotherapy can help improve the outlook for people with SCLC.

Little research is available on the effectiveness of immunotherapy as the sole, first-line treatment for SCLC. Since SCLC tends to be aggressive, the risk for complications is higher if chemotherapy isn’t administered as soon as possible.

Immunotherapy research is still relatively new, so there’s a lot that researchers don’t know. But dozens of clinical trials are currently examining the potential benefits of immunotherapy.

The majority of clinical trials have examined the combined effect of immunotherapy with chemotherapy. Studies have found mixed results about the effectiveness of immunotherapy:

  • In an older 2013 phase II clinical study, participants with extensive-stage SCLC were either given chemotherapy and a placebo or chemotherapy and a monoclonal antibody called ipilimumab. The researchers found only a minimal benefit of ipilimumab compared to a placebo.
  • A 2016 phase III clinical trial failed to find a benefit for overall survival with extensive-stage SCLC when combining ipilimumab with chemotherapy compared to chemotherapy and a placebo.
  • A 2018 phase III clinical trial examined the effect of the monoclonal antibody atezolizumab combined with chemotherapy in extensive-stage SCLC. The researchers found that atezolizumab increased overall survival compared to a placebo by 2 months.
  • A 2019 phase III clinical trial examined the potential benefit of the immunotherapy drug durvalumab plus chemotherapy as a first-line treatment for people with SCLC that had spread to other parts of their body. The researchers found a significant improvement in overall survival in participants who received durvalumab compared to participants in the control group.

You can find the latest list of clinical trials that are actively recruiting participants in the United States by visiting the U.S. National Library of Medicine website and searching for keywords like “immunotherapy” and “small cell lung cancer.” The exact number of trials can vary over time.

Most clinical trials are examining the effectiveness of immunotherapy in combination with chemotherapy. Some specific drugs being investigated are:

  • ipilimumab
  • nivolumab
  • durvalumab
  • atezolizumab
  • pembrolizumab
  • M7824

If you have SCLC, you may be able to find clinical trials in your area that you can participate in. Government agencies, universities, and drug companies all run clinical trials.

Researchers have yet to determine how best to use immunotherapy to treat SCLC.

It may be used for people in the early stages of the disease in combination with chemotherapy, but may also be used in later stages if you don’t respond to initial treatments.

It’s not entirely clear who makes the best candidate for SCLC. But in general, people with autoimmune conditions or chronic infections may not make good candidates due to the risk of making the immune system overly active.

According to the American Cancer Society, immunotherapy can lead to one or more of the following side effects:

You can also experience a reaction after receiving immunotherapy drugs that can include symptoms like:

Immunotherapy can also lead to autoimmune reactions. This happens when the immune system attacks parts of your own body. In some cases, autoimmune reactions can severely damage vital organs and be life threatening.

Talk with a healthcare professional as soon as possible if you experience any concerning symptoms like those listed above.

SCLC tends to be aggressive. About 70 percent of cases aren’t diagnosed until it has already spread throughout the body.

It’s not currently clear how effective immunotherapy is for treating SCLC. Most research has examined immunotherapy combined with chemotherapy, and results have been mixed.

Dozens of clinical trials are currently being run in the United States and worldwide to examine how immunotherapy may help people with SCLC. Many are accepting volunteers to help better understand the relationship between immunotherapy and the prognosis of SCLC.