Lung cancer treatment has shifted dramatically in the last 20 years. For decades, the standard of care was cytotoxic chemotherapy, but today immune checkpoint inhibitors anchor regimens across nearly every disease stage, according to a 20-year perspective published in The Journal of Thoracic Oncology.
From Poison to Immune Activation
Therapies that harness a patient’s immune system have transformed the biology and prognosis of lung cancer. The field moved from conventional cytotoxic chemotherapy toward immune activation after deepening understanding of tumor immunology and antigen presentation. Checkpoint inhibition began as monotherapy before evolving into combination regimens for non–small cell lung cancer (NSCLC) and small cell lung cancer (SCLC).
This progression built on the 2015 FDA approval of nivolumab for previously treated squamous NSCLC. That milestone opened the door to a wave of indications spanning first-line metastatic disease, perioperative treatment, and limited-stage SCLC. The cumulative effect has meaningfully prolonged survival for a disease once defined by uniformly poor outcomes.
Reviewing the history reveals a synthesis of clinical and translational progress. The analysis traces the biological rationale for checkpoint inhibition and its integration across disease stages with agents including pembrolizumab, nivolumab, atezolizumab, durvalumab, and cemiplimab. Combination strategies with chemotherapy and antibody-drug conjugates followed these initial monotherapy successes.
Biomarkers and Survival Gains
Checkpoint inhibition is now visible on Kaplan-Meier curves for some patients with NSCLC, creating a long-term survival “tail.” In the key KEYNOTE-001 trial (NCT01295827), 5-year overall survival reached 23.2% among treatment-naive patients and 15.5% among previously treated patients. In KEYNOTE-024 (NCT02142738), survival reached 31.9%. These figures compare with the historical 5-year survival of roughly 5% for metastatic NSCLC in the chemotherapy era.
Patients with high PD-L1 expression or high tumor mutational burden often respond better to these treatments, though neither marker reliably predicts benefit on its own. The science of biomarkers has evolved alongside the drugs, shaping patient selection over time. This shift is particularly meaningful for people who would have faced a very short prognosis with older treatments.
Resistance and Toxicity Challenges
Not every disease setting has benefited equally. In extensive-stage SCLC, survival curves across treatment arms tend to converge over time, reflecting a lack of sustained immunologic disease control. Tumors with low neoantigen burden or proficient DNA-repair capacity often show primary resistance. Acquired resistance mechanisms include T-cell exhaustion and upregulation of alternative checkpoints like TIM-3.
Immune-related adverse events remain a significant consideration. Dermatologic toxicity affects 20% to 40% of patients, mostly low grade. Gastrointestinal issues like diarrhea and colitis occur in 10% to 30% of cases. Less common but more severe effects include pneumonitis (3% to 5%), hepatic toxicity (5% to 10%), endocrine issues (5% to 15%), and myocarditis (less than 1%). These risks climb further with dual-checkpoint-inhibitor combinations.
