Side effects of small cell lung cancer treatment

Side effects are a common part of treatment for small cell lung cancer (SCLC). Many are short-lived and improve soon after treatment ends. Some treatments can cause longer-term effects, but this is less common.¹

The side effects that people with small cell lung cancer experience depend on the treatments they receive. This page outlines some of the side effects linked with common treatments for small cell lung cancer.

Keeping a record of any symptoms you notice can help your healthcare team manage side effects early – there is a lot of support available.

Chemotherapy

Chemotherapy works by killing cells that grow and divide quickly. This includes cancer cells but also some healthy cells, such as hair follicles, cells in the bone marrow, and cells that line the mouth and digestive system.

Some common side effects of chemotherapy for lung cancer are listed below. Different people will experience side effects differently, depending on the specific drugs used, the doses given, and how your body reacts to the treatment. Most side effects go away after chemotherapy is finished. Your physician will monitor you for side effects and can recommend supportive treatments.

Common side effects of chemotherapy for lung cancer include:

Anemia
Bleeding and bruising easily.
Constipation or diarrhea.
Fatigue.
Hair loss.
Loss of appetite or weight loss.
Nausea.

People who have chemotherapy are at increased risk of getting an infection. Infections can become serious quickly, so it is important to contact your healthcare team if you have symptoms of infection, including a high temperature or feeling generally unwell.

Immunotherapy

Immunotherapy works by helping the immune system recognize and attack cancer cells. Sometimes, it can cause immune cells to attack healthy cells in the body, causing side effects.

Side effects of immunotherapy can affect any part of the body, but it is most common to notice effects on the skin, the gut, the joints, the hormone-producing glands (such as the thyroid), and the lungs.

One of the most common side effects of immunotherapy is fatigue, but you may also notice things like:

Breathlessness.
Diarrhea.
Skin rashes or itching.
Sore or weak muscles.
Stiff, sore, or swollen joints.

Some side effects of immunotherapy can become serious if they are not treated quickly. They can start during treatment or sometimes months after treatment has finished. Your healthcare team will tell you what to look out for. It is important to keep a record of your symptoms and speak to your healthcare team about how you are feeling.

Some newer types of immunotherapy, such as T-cell engaging therapies, can also cause a reaction called cytokine release syndrome (CRS). This is caused by a very strong immune response and may lead to fever, chills, or dizziness – usually only after first few doses. These therapies are usually given using ‘step-up’ dosing (where a small dose is given to start with, and this is increased over the next doses, up to the full-strength dose) to reduce the risk of severe CRS. You will be monitored closely during the first few doses, with other medication given if needed to manage these effects. Some patients might also experience a change in taste (dysgeusia) – your healthcare team will be able to discuss oral care, dietary changes, and supplements that can help.

Less commonly, these treatments may also cause immune effector cell-associated neurotoxicity syndrome (ICANS), which can affect the brain and may cause confusion, sleepiness, headache, or difficulty speaking. Your healthcare team will monitor you closely during early treatment and can treat these symptoms quickly if they occur. Many people are able to continue treatment with monitoring and support.

Radiotherapy

Radiotherapy is not painful, and most people feel no effects during treatment itself. Side effects usually begin about a week or so after therapy starts and gradually worsen during the course of treatment. Side effects usually improve between 2 and 4 weeks after treatment finishes.

Common side effects of radiotherapy for lung cancer include:

Breathlessness or cough.
Chest pain or discomfort.
Difficulty swallowing.
Hair loss around the treated area.
Loss of appetite.
Nausea or vomiting.
Skin changes in the treated area – often similar to sunburn.
Fatigue.

Rarely, radiotherapy for lung cancer can cause pneumonitis. This is where the lung becomes inflamed, causing sudden breathlessness or a cough. Contact your healthcare team straightaway if you have these symptoms, so they can support you.

Combining radiotherapy with chemotherapy often leads to more side effects.

Surgery (used only in a small number of early-stage cases)

Surgery is less commonly used in small cell lung cancer compared with other types of lung cancer. The most common side effects of surgery for lung cancer are pain, swelling, and scars. Pain and swelling are usually worst in the first week or so after surgery and then gradually improve. Your healthcare team will give you painkillers and work with you to find the right dose based on how you are feeling.

Breathlessness can be normal after surgery for lung cancer. How breathless someone feels depends on the type of surgery performed and how well they were before surgery.

Breathlessness should get better over time as the remaining lung adapts and compensates for the removed tissue. You should tell your healthcare team if your breathlessness is getting worse, is not improving, or if breathing becomes very difficult.

People who have surgery for lung cancer can also be at risk of infection after surgery. Tell your healthcare team if you notice symptoms such as fever, redness or discharge around the wound, or if you feel generally unwell.

References

National Comprehensive Cancer Network® (NCCN®). NCCN guidelines for patients: Small cell lung cancer, 2024. https://www.nccn.org/patients/guidelines/content/PDF/SCLC-patient-guideline.pdf. Accessed Mar 31, 2026.
National Cancer Institute. Chemotherapy to treat cancer. https://www.cancer.gov/about-cancer/treatment/types/chemotherapy. Updated May 15, 2025. Accessed Mar 31, 2026.
Cancer Research UK. Chemotherapy for lung cancer. https://www.cancerresearchuk.org/about-cancer/lung-cancer/treatment/chemotherapy-treatment. Updated Jan 14, 2026. Accessed Mar 31, 2026.
Cancer Research UK. Immunotherapy and its side effects. https://www.cancerresearchuk.org/health-professional/treatment-and-other-post-diagnosis-issues/immunotherapy-and-its-side-effects. Accessed Mar 31, 2026.
Macmillan Cancer Support. Immunotherapy. https://www.macmillan.org.uk/cancer-information-and-support/treatment/types-of-treatment/immunotherapy. Updated May 1, 2024. Accessed Mar 31, 2026.
MedlinePlus. Tarlatamab injection. https://medlineplus.gov/druginfo/meds/a624037.html. Accessed Mar 31, 2026.
Tarlatamab. Prescribing Information (FDA). 2024.
Cancer Research UK. Side effects of lung cancer radiotherapy. https://www.cancerresearchuk.org/about-cancer/lung-cancer/treatment/radiotherapy/side-effects. Updated Oct 10, 2025. Accessed Mar 31, 2026.
Cancer Research UK. After lung cancer surgery. https://www.cancerresearchuk.org/about-cancer/lung-cancer/treatment/surgery/after-surgery. Updated Oct 8, 2025. Accessed Mar 31, 2026.
Cancer Research UK. Problems after lung cancer surgery. https://www.cancerresearchuk.org/about-cancer/lung-cancer/treatment/surgery/possible-problems. Updated Oct 8, 2025. Accessed Mar 31, 2026.