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Non-Small Cell Lung Cancer (C34.90)

Non–small cell lung cancer (NSCLC) is the most common form of lung cancer, accounting for roughly 85% of cases, and is defined less by histology than by its molecular diversity. Modern management is driven by the identification of oncogenic drivers—such as EGFR, ALK, KRAS, MET, and RET—and by immune features like PD-L1 expression, which together determine therapy selection. Treatment has shifted from uniform chemotherapy to precision strategies that include targeted tyrosine kinase inhibitors, immune checkpoint inhibitors, antibody–drug conjugates, and rational combinations. Despite major advances and improved survival, resistance and disease evolution remain central challenges, making NSCLC a dynamic testbed for next-generation precision oncology.

Causes

The etiology of non–small cell lung cancer (NSCLC) reflects a multistep process of cumulative genomic injury interacting with host susceptibility and microenvironmental pressures. The dominant causal exposure remains tobacco smoke, which delivers polycyclic aromatic hydrocarbons and nitrosamines that generate bulky DNA adducts and characteristic mutational signatures (notably C>A transversions) in key oncogenes and tumor suppressors. However, a substantial and rising subset of NSCLC—particularly adenocarcinoma—occurs in never-smokers, where alternative drivers such as activating mutations in EGFR or rearrangements involving ALK and ROS1 predominate. Environmental contributors including radon exposure, asbestos, air pollution (PM2.5), and occupational carcinogens induce chronic epithelial injury, oxidative stress, and inflammation, fostering genomic instability and aberrant repair. Loss of tumor suppressors such as TP53 and STK11 further compromises genomic surveillance and metabolic control, enabling clonal expansion. Increasingly, NSCLC is viewed not as a single-cause malignancy but as the evolutionary consequence of repeated epithelial damage, mutational selection, immune editing, and microenvironmental adaptation—an interplay that defines both its origin and its biologically diverse therapeutic vulnerabilities.

Pathophysiology

The pathophysiology of non–small cell lung cancer (NSCLC) is defined by dysregulated signal transduction, impaired genomic control, and dynamic tumor–microenvironment co-evolution. Activating mutations in oncogenic drivers such as EGFR, KRAS, and rearrangements involving ALK or ROS1 constitutively engage downstream MAPK and PI3K–AKT–mTOR cascades, promoting unchecked proliferation, survival signaling, metabolic reprogramming, and resistance to apoptosis. Concurrent loss of tumor suppressors such as TP53 and RB1 disrupts cell-cycle checkpoints and genomic integrity, accelerating clonal evolution. At the tissue level, malignant epithelial cells remodel their microenvironment through angiogenic signaling (e.g., VEGF upregulation), extracellular matrix degradation, and immune modulation—often via PD-L1 expression that engages PDCD1 on T cells to induce functional exhaustion. Tumor heterogeneity emerges through branching evolutionary dynamics, with subclones acquiring secondary resistance mutations (e.g., EGFR T790M, MET amplification) under therapeutic pressure. Thus, NSCLC pathophysiology reflects a systems-level disruption of signaling topology, immune surveillance, and temporal control of cellular growth, rather than a single linear oncogenic event.

Clinical features

The clinical presentation of non–small cell lung cancer (NSCLC) is often insidious, with symptoms emerging only after significant local invasion or metastatic spread. Early-stage disease may be asymptomatic or manifest with nonspecific complaints such as persistent cough, mild dyspnea, fatigue, or unexplained weight loss. As the primary tumor enlarges, patients may develop hemoptysis, pleuritic chest pain, or recurrent pneumonia due to airway obstruction. Locally advanced disease can produce hoarseness (recurrent laryngeal nerve involvement), superior vena cava syndrome, or chest wall pain. Metastatic dissemination commonly involves brain (headache, seizures, focal neurologic deficits), bone (pain, pathologic fractures), liver (hepatomegaly, abnormal liver enzymes), and adrenal glands. Paraneoplastic phenomena—including hypercalcemia (often in squamous histology), SIADH, or digital clubbing—reflect systemic biologic activity of the tumor. Importantly, symptom profile may vary by molecular subtype and metastatic pattern, underscoring the need for high clinical suspicion and early imaging in at-risk populations.

Diagnosis

Diagnosis of non–small cell lung cancer (NSCLC) begins with imaging—typically chest radiography followed by high-resolution CT scanning—to characterize pulmonary masses, nodal involvement, and potential metastatic disease. PET–CT is frequently used for metabolic staging, while brain MRI evaluates central nervous system spread in appropriate patients. Definitive diagnosis requires tissue acquisition via bronchoscopy, endobronchial ultrasound–guided biopsy, CT-guided percutaneous biopsy, or surgical sampling, enabling histologic classification (adenocarcinoma, squamous, large cell). Critically, contemporary diagnosis extends beyond morphology to comprehensive molecular profiling: next-generation sequencing panels assess actionable alterations such as mutations in EGFR and KRAS, fusions involving ALK, and other driver events, while immunohistochemistry evaluates PD-L1 expression via CD274 to guide immunotherapy selection. Staging is completed using the TNM system, integrating tumor size, nodal status, and distant metastasis. Thus, NSCLC diagnosis is now a multidisciplinary, molecularly informed process that directly determines therapeutic strategy and prognostic stratification.

Mechanism of action videos

Biological pathways

  • Phosphatidylinositol signaling system
  • PI3K-Akt signaling pathway
  • Non-small cell lung cancer
  • Signaling by Receptor Tyrosine Kinases
  • MAPK signaling pathway
  • ErbB signaling pathway
  • Cell cycle
  • Calcium signaling pathway
  • Apoptosis
  • Gap junction assembly
  • Post NMDA receptor activation events
  • Activation of NMDA receptors and postsynaptic events
  • Diseases of signal transduction by growth factor receptors and second messengers
  • Signaling by ERBB2 KD Mutants
  • Signaling by LTK in cancer
  • GRB2 events in ERBB2 signaling
  • RHO GTPases activate IQGAPs
  • Microtubule-dependent trafficking of connexons from Golgi to the plasma membrane
  • Transport of connexons to the plasma membrane
  • Signaling by ERBB2
  • Kinesins
  • ERBB2 Activates PTK6 Signaling
  • ERBB2 Regulates Cell Motility
  • Activation of AMPK downstream of NMDARs
  • Neurotransmitter receptors and postsynaptic signal transmission
  • Sealing of the nuclear envelope (NE) by ESCRT-III
  • PKR-mediated signaling
  • Post-chaperonin tubulin folding pathway
  • The role of GTSE1 in G2/M progression after G2 checkpoint
  • Signaling by PTK6
  • MHC class II antigen presentation
  • Aggrephagy
  • Constitutive Signaling by Aberrant PI3K in Cancer
  • Prefoldin mediated transfer of substrate to CCT/TriC
  • Assembly and cell surface presentation of NMDA receptors
  • Signal Transduction
  • Formation of tubulin folding intermediates by CCT/TriC
  • COPI-dependent Golgi-to-ER retrograde traffic
  • Gap junction trafficking
  • Developmental Biology

Clinical trials

  • A Randomized, Double-blind Study to Compare the Pharmacokinetics Between ABP 234 and Keytruda® (Pembrolizumab) in Participants With Early-stage Non-squamous Non-small Cell Lung Cancer as Adjuvant Treatment Following Resection and Platinum-based Chemotherapy
  • A Randomized Phase III Trial of Induction/Consolidation Atezolizumab (NSC #783608) + SBRT Versus SBRT Alone in High Risk, Early Stage NSCLC
  • A Phase 1 Trial of the ATR Inhibitor BAY 1895344 in Combination With Cisplatin and With Cisplatin Plus Gemcitabine in Advanced Solid Tumors With an Emphasis on Urothelial Carcinoma
  • Randomized Phase III Trial INcorporating Pathologic Complete ReSponse in Participants With Early StaGe Non Small Cell Lung Cancer to Optimize ImmunotHerapy in The AdjuvanT Setting (INSIGHT)
  • MATCH Treatment Subprotocol H: Phase II Study of Dabrafenib and Trametinib in Patients With Tumors With BRAF V600E or V600K Mutations (Excluding Melanoma, Thyroid Cancer, Colorectal Adenocarcinoma, and Non-Small Cell Lung Cancer)
  • A Phase Ia/Ib Dose-Escalation and Dose-Expansion Study Evaluating the Safety, Pharmacokinetics, and Activity of GDC-6036 as a Single Agent and in Combination With Other Anti-cancer Therapies in Patients With Advanced or Metastatic Solid Tumors With a KRAS G12C Mutation
  • A Phase II Study of Ivonescimab as Monotherapy or in Combination With Platinum/Pemetrexed Chemotherapy in Patients With Advanced Non-small Cell Lung Cancer (NSCLC) Harboring Actionable Genomic Alterations (AGAs)
  • A Phase 1 Trial of MLN0128 (TAK-228) in Combination With Osimertinib (AZD9291) in Advanced EGFR Mutation Positive Non-Small Cell Lung Cancer (NSCLC) After Progression on a Previous EGFR Tyrosine Kinase Inhibitor
  • The Effect of Preoperative Structured Exercise Programme on Postoperative Pain Severity, Recovery Level, Discharge Time and Quality of Life in Patients With Non-Small Cell Lung Cancer: Randomised Controlled Study
  • Phase I Study to Evaluate Safety, Tolerability, Pharmacokinetics and Anti-Tumor Activity of WSD0922-FU
  • Randomized Phase III Study of Combination Osimertinib (AZD9291) and Bevacizumab Versus Osimertinib (AZD9291) Alone as First-Line Treatment for Patients With Metastatic EGFR-Mutant Non-Small Cell Lung Cancer (NSCLC)
  • A Phase III Randomized, Open-Label, Multi-Center, Global Study of MEDI4736 in Combination With Tremelimumab Therapy Versus Standard of Care Platinum-Based Chemotherapy in First-Line Treatment of Patients With Advanced or Metastatic Non Small-Cell Lung Cancer (NSCLC).
  • A Phase I Clinical Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of AST2303 Tablets (ABK3376 Tablets) in Patients With Advanced or Metastatic Non-Small Cell Lung Cancer
  • ATOM2: A Randomized Phase II Trial on Ablative Therapy to Oligoresidual Metastasis in EGFR Mutated Non-small Cell Lung Cancer After Osimertinib Treatment
  • Knight Cancer Institute Study of Histology-Agnostic Immunotherapy With Focus on Timing: - Knight SHIFT - A Prospective, Multi-Histology Pragmatic Study
  • PHILUCA: The Development of Muscle Mass, Muscle Strength, and Muscle Function in Patients With Lung Cancer During Cancer Treatment
  • DART: Dual Anti-CTLA-4 and Anti-PD-1 Blockade in Rare Tumors
  • A Phase III, Randomized, Multicentre, Open Label Study to Assess the Efficacy and Safety of Firmonertinib Versus Platinum Based Chemotherapy as First-line Treatment for Locally Advanced or Metastatic Non-small Cell Lung Cancer Patients With EGFR PACC Mutation or EGFR l861q Mutation
  • A Randomized Phase III Trial of Chemo-Immunotherapy vs Immunotherapy Alone for the Vulnerable Older Adult With Advanced Non-Small Cell Lung Cancer: The ACHIEVE Study
  • Cancer Moonshot Biobank Research Protocol
  • Adjuvant Lung Cancer Enrichment Marker Identification and Sequencing Trial (ALCHEMIST)
  • A Randomised Phase III Trial of Adjuvant Cemiplimab in Patients With Resected Stage II-IIIA NSCLC Who Have Not Received Prior Adjuvant Chemotherapy
  • Pilot Trial of Nivolumab Plus Cabozantinib for Advanced Solid Tumors in Patients With HIV Infection
  • Neoadjuvant Platform Trial in Patients With Surgically Resectable Non-Small Cell Lung Cancer (NSCLC)
  • Evaluating Adjuvant Atezolizumab or Atezolizumab and Hyaluronidase-TQJS to Prevent Recurrence in Stage I Non-Small Cell Lung Cancer (NSCLC): A Randomized Phase III Trial (AASI-NSCLC)
  • A Phase 3, Multicenter, Randomized, Open-label Study Evaluating Efficacy of Sotorasib Platinum Doublet Combination Versus Pembrolizumab Platinum Doublet Combination as a Front-Line Therapy in Subjects With Stage IV or Advanced Stage IIIB/C Nonsquamous Non-Small Cell Lung Cancers, Negative for PD-L1, and Positive for KRAS p.G12C (CodeBreaK 202)
  • A Dose-Escalation and Expansion Study of the Safety and Efficacy of XL092 in Combination With Immuno-Oncology Agents in Subjects With Unresectable Advanced or Metastatic Solid Tumors
  • A Phase 2 Study to Investigate Ubamatamab With and Without REGN7075 in Treatment-Experienced Participants With Advanced/Metastatic Non-Small Cell Lung Cancer (NSCLC)
  • A Phase 1/1b Study Evaluating the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Efficacy of AMG 410 Alone and in Combination With Other Agents in Participants With KRAS Altered Advanced or Metastatic Solid Tumors
  • Open-label Phase II Efficacy Study of Repotrectinib in Frail (PS ≥2) and/or Elderly Patients With ROS1-rearranged Advanced NSCLC
  • Adjuvant Nivolumab in Resected Lung Cancers (ANVIL)-A Randomized Phase III Study of Nivolumab After Surgical Resection and Adjuvant Chemotherapy in Non-Small Cell Lung Cancers
  • A Phase III, Randomized, Double-blind, Multicenter, Global Study of Rilvegostomig or Pembrolizumab in Combination With Platinum-based Chemotherapy for the First-line Treatment of Patients With Metastatic Non-squamous Non-small Cell Lung Cancer Whose Tumors Express PD-L1 (ARTEMIDE-Lung03)
  • Phase II Study of Osimertinib (AZD9291) in Advanced NSCLC Patients With Exon 20 Insertion Mutations in EGFR
  • Randomized Study of Erlotinib Vs Observation in Patients With Completely Resected Epidermal Growth Factor Receptor (EGFR) Mutant Non-Small Cell Lung Cancer (NSCLC)
  • A Phase 2 Single-Arm Study of Neoadjuvant Chemo-Immunotherapy and Surgical Resection in Locally Advance Non-Small Cell Lung Cancer (NSCLC) With N3 Lymph Node Involvement
  • A Phase III, International, Multicenter, Randomized, Controlled, Open-label Clinical Study Evaluating Furmonertinib Plus Platinum-based Doublet Chemotherapy Versus Osimertinib in Patients With Epidermal Growth Factor Receptor (EGFR) Sensitizing Mutation-Positive Non-squamous Non-Small Cell Lung Cancer (NSCLC) and Brain Metastases
  • A Phase 2, Open-Label, Randomized, Global Study of Three Telisotuzumab Vedotin Regimens in Subjects With Previously Treated c-Met Overexpressing, EGFR Wildtype, Locally Advanced/Metastatic Non-Squamous Non-Small Cell Lung Cancer
  • A Randomized Phase 2 Platform Study to Evaluate Cemiplimab Plus Chemotherapy Versus Cemiplimab Plus Chemotherapy Plus Other Cancer Treatments for the Perioperative Treatment of Patients With Resectable Non-Small Cell Lung Cancer
  • A Biomarker Study of Low-Dose IL-2 Plus Pembrolizumab in Patients With Stage IV Non-Small Cell Lung Cancer (NSCLC)
  • Phase I Study of the CDK4/6 Inhibitor Palbociclib (PD-0332991) in Combination With the MEK Inhibitor Binimetinib (MEK162) for Patients With Advanced KRAS Mutant Non-Small Cell Lung Cancer

Therapeutic area: Oncology