Systemic Therapy for Locally Advanced and Metastatic Non-Small Cell Lung Cancer: A Review

Non-small cell lung cancer remains the leading cause of cancer death in the United States. Until the last decade, the 5-year overall survival rate for patients with metastatic non-small cell lung cancer was less than 5%. Improved understanding of the biology of lung cancer has resulted in the development of new biomarker-targeted therapies and led to improvements in overall survival for patients with advanced or metastatic disease.

Systemic therapy for metastatic non-small cell lung cancer is selected according to the presence of specific biomarkers. Therefore, all patients with metastatic non-small cell lung cancer should undergo molecular testing for relevant mutations and expression of the protein PD-L1 (programmed death ligand 1). Molecular alterations that predict response to treatment (eg, EGFR mutations, ALK rearrangements, ROS1 rearrangements, and BRAF V600E mutations) are present in approximately 30% of patients with non-small cell lung cancer. Targeted therapy for these alterations improves progression-free survival compared with cytotoxic chemotherapy. For example, somatic activating mutations in the EGFR gene are present in approximately 20% of patients with advanced non-small cell lung cancer. Tyrosine kinase inhibitors such as gefitinib, erlotinib, and afatinib improve progression-free survival in patients with susceptible EGFR mutations. In patients with overexpression of ALK protein, the response rate was significantly better with crizotinib (a tyrosine kinase inhibitor) than with the combination of pemetrexed and either cisplatin or carboplatin (platinum-based chemotherapy) (74% vs 45%, respectively; P < .001) and progression-free survival (median, 10.9 months vs 7.0 months; P < .001). Subsequent generations of tyrosine kinase inhibitors have improved these agents. For patients without biomarkers indicating susceptibility to specific targeted treatments, immune checkpoint inhibitor-containing regimens either as monotherapy or in combination with chemotherapy are superior vs chemotherapy alone. These advances in biomarker-directed therapy have led to improvements in overall survival. For example, the 5-year overall survival rate currently exceeds 25% among patients whose tumors have high PD-L1 expression (tumor proportion score of ≥50%) and 40% among patients with ALK-positive tumors.

Improved understanding of the biology and molecular subtypes of non-small cell lung cancer have led to more biomarker-directed therapies for patients with metastatic disease. These biomarker-directed therapies and newer empirical treatment regimens have improved overall survival for patients with metastatic non-small cell lung cancer.