Understanding Immunotherapy in Small Cell Lung Cancer
April 14, 2026
Small cell lung cancer (SCLC) is 1 of the 2 main types of lung cancer and accounts for about 15 out of 100 (15%) cases. For decades, treatment for SCLC included chemotherapy, radiation therapy, or surgery if diagnosed in early stages.
It wasn’t until 2018 that the first immunotherapy for SCLC was approved by the Food and Drug Administration (FDA). This was an important advancement in treating SCLC, as immunotherapy works very differently from other treatment types. In October 2025, another breakthrough occurred in the field of immunotherapy when a new type of immunotherapy, a T-cell engager, was approved for SCLC.
These advancements bring hope and optimism to SCLC and expand treatment options. Understanding immunotherapy, how it works, and when it may be used helps you have informed conversations with your healthcare team and stay involved in decision-making. This is important because being knowledgeable allows you to advocate for what matters most to you.
What is immunotherapy?
Your immune system defends your body against germs and diseases that can cause illness. Most of the time, it can tell which cells are healthy and which are not. This enables the immune system to target disease and germ cells without harming healthy cells.
When your immune system detects cancer cells, it goes to work destroying them. Sometimes, it has trouble finding cancer cells because they can appear like healthy cells. Immunotherapy helps your immune system find and attack cancer cells.
Types of immunotherapy
Currently, there are 2 main types of immunotherapies used in SCLC: checkpoint inhibitors and T-cell engagers. They each work in very different ways and are used in different points in treatment.
Checkpoint inhibitors
How do they work?
Cancer cells can hide from the immune system by attaching themselves to immune cells. Cancer cells can attach to immune cells at an area called a checkpoint. This sends a signal to your immune system that the cancer cell is healthy, which prevents the immune system cell from attacking it. A checkpoint inhibitor works by blocking cancer cells from attaching to immune system cells, allowing the immune system to better attack the cancer.
When are they used to treat SCLC?
Imfinzi (durvalumab) and Tecentriq (atezolizumab); however, recent clinical trials have broadened their approved uses in different ways.
- Limited-stage SCLC (stages 1, 2, 3): Imfinzi (durvalumab) can be used after chemotherapy and radiation treatments are complete and may be continued for up to 2 years.
- Extensive-stage SCLC (stage 4): Imfinzi (durvalumab) or Tecentriq (atezolizumab) can be used in combination with chemotherapy. Imfinzi may be continued alone after chemotherapy is completed for as long as it is effective and well-tolerated. This is called maintenance therapy. Tecentriq (atezolizumab) may also be used as maintenance therapy either alone or combined with the chemotherapy drug Lurbinectedin.
T-cell engagers
How do they work?
T-cell engagers, such as Imdeltra (tarlatmab), work like a matchmaker. They attach to a T-cell (a type of immune cell that fights germs and diseases) and a cancer cell, bringing them close together. This connection helps your immune system find and attack cancer cells.
When are they used to treat SCLC?
T-cell engagers are FDA-approved for use in extensive-stage SCLC that has spread during or after chemotherapy.
Immunotherapy side effects
The side effects you may experience from immunotherapy will be unique to you. Some common side effects are mild, while others can be more severe. Immunotherapy boosts your immune system's activity, which can sometimes impact healthy cells and organs, leading to inflammation. This requires prompt medical attention.
Ask a member of your healthcare team what common and more serious side effects may occur with your specific type of immunotherapy and know when you should seek immediate medical care.
The future of immunotherapy in SCLC
Immunotherapy is not 1 single treatment; it’s a growing toolbox of therapies. In fact, there are many clinical trials currently underway that focus on:
- Expanding how the currently approved immunotherapies are used to improve outcomes, including using them in earlier stages or combined with other treatments
- Developing new immunotherapy treatments that work differently from the current options
- Exploring ways to boost the body’s immune system and impact the tumor to make it easier to target and attack Questions for your healthcare team
It’s important to talk to your healthcare team about all your treatment options, including immunotherapy. The following questions may be helpful to ask in your conversation:
- Is immunotherapy right for me?
- What side effects should I be aware of with the type of immunotherapy recommended for me?
- Are there any clinical trials that may be right for me?
To learn about our SCLC program or clinical trials, connect with our free HelpLine by calling 1-800-298-2436, emailing support@go2.org, or filling out our online form.
Lung cancer questions? Contact our free HelpLine at support@go2.org or 1-800-298-2436.