Common Side Effects of Lung Cancer Immunotherapy: What Patients Should Know

Understanding Immunotherapy for Lung Cancer

Immunotherapy has revolutionized the treatment landscape for non-small cell lung cancer (NSCLC), offering new hope to patients with advanced disease. The most widely used immunotherapies target the PD-1 and PD-L1 pathways, which help cancer cells evade detection by the immune system. By blocking these checkpoints, drugs like pembrolizumab, nivolumab, and atezolizumab empower the body's immune system to recognize and attack tumor cells more effectively.

Frequent Immune-Related Adverse Events

While immunotherapy is generally better tolerated than traditional chemotherapy, it can trigger a range of immune-mediated side effects because it activates the immune system broadly. These adverse reactions—often referred to as immune-related adverse events (irAEs)—can affect nearly any organ system in the body. Most are mild to moderate, but early recognition and intervention are crucial to prevent complications.

Skin Reactions: Often the First Sign

Skin toxicities are among the most common side effects, typically appearing within weeks of starting treatment. Patients may experience rash, itching (pruritus), or dry skin. In rare cases, severe conditions such as bullous dermatitis, Stevens-Johnson syndrome, or toxic epidermal necrolysis can develop. These require immediate medical attention and often discontinuation of therapy. Early use of topical steroids or antihistamines can help manage milder symptoms.

Endocrine System Complications

Immune checkpoint inhibitors can disrupt hormone-producing glands, leading to endocrinopathies. The most frequently observed include:

• Hypothyroidism: Fatigue, weight gain, and cold intolerance are typical signs.
• Hyperthyroidism: May present with anxiety, palpitations, and unintended weight loss.
• Hypophysitis (pituitary inflammation): Can cause headaches, vision changes, and hormonal imbalances.
• Adrenal insufficiency: Symptoms include dizziness, low blood pressure, and nausea.
• Immune-mediated diabetes: Sudden onset hyperglycemia or diabetic ketoacidosis may occur, though rarely.

Regular monitoring of thyroid function and cortisol levels is recommended during treatment.

Liver Toxicity: Monitoring Liver Enzymes

Hepatitis associated with immunotherapy usually presents with elevated liver enzymes (ALT and AST) and sometimes increased bilirubin. Most cases are asymptomatic and detected through routine blood tests. However, jaundice, dark urine, or abdominal discomfort may signal more serious liver involvement. Corticosteroids are often prescribed if liver enzyme levels rise significantly.

Gastrointestinal Issues: Diarrhea and Colitis

Immune-related colitis can range from mild diarrhea to severe, life-threatening inflammation of the colon. Patients may also experience abdominal pain, cramping, or bloody stools. Mild cases may be managed with anti-diarrheal medications, while moderate to severe colitis typically requires corticosteroids and temporary or permanent discontinuation of immunotherapy.

Pulmonary and Muscular Side Effects

Immune checkpoint inhibitor pneumonitis is a potentially serious lung complication, occurring in approximately 3–5% of patients. Symptoms include cough, shortness of breath, and low oxygen levels. Imaging often reveals patchy infiltrates or ground-glass opacities. Prompt treatment with steroids improves outcomes.

Myositis, or muscle inflammation, is less common but can lead to muscle weakness, pain, and elevated creatine kinase (CK) levels. In rare instances, it may progress to rhabdomyolysis—a dangerous condition involving muscle breakdown.

When to Seek Medical Help

Although most immune-related side effects are manageable, some can escalate quickly and become life-threatening. Patients should report any new or worsening symptoms promptly, including fatigue, unexplained weight changes, breathing difficulties, persistent diarrhea, or skin changes. Early diagnosis through lab tests, imaging, and clinical evaluation allows for timely intervention and better long-term outcomes.

Conclusion: Balancing Efficacy and Safety

Immunotherapy represents a major advancement in lung cancer care, but its unique mechanism of action brings distinct safety considerations. Awareness of potential side effects empowers both patients and healthcare providers to act swiftly when issues arise. With proper monitoring and multidisciplinary management, the benefits of immunotherapy can be maximized while minimizing risks to quality of life.