Lung Cancer

Lung cancer begins in cells of the lung. It is broadly divided into non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLC includes adenocarcinoma, squamous cell carcinoma, and several less common histologic types. SCLC generally grows and spreads more rapidly and is often treated differently from NSCLC.

Tobacco smoking is the most important preventable risk factor, but lung cancer also occurs in people who have never smoked. Some lung adenocarcinomas in never-smokers contain targetable driver alterations. Diagnosis usually requires imaging and tissue sampling. Treatment decisions depend on histologic type, stage, overall health, and molecular test results.

• A persistent or worsening cough
• Coughing up blood or blood-streaked sputum
• Chest pain, especially when breathing deeply or coughing
• Shortness of breath, wheezing, or hoarseness
• Repeated or difficult-to-resolve pneumonia or bronchitis
• Unexplained weight loss, reduced appetite, or fatigue
• Symptoms from spread to other organs, such as bone pain, headache, neurologic changes, or liver abnormalities

Early lung cancer may cause no symptoms. These findings can also result from infections or other noncancerous conditions and cannot confirm cancer on their own.

• Tobacco use, including cigarettes, cigars, and pipes
• Secondhand smoke exposure
• Radon exposure
• Occupational or environmental exposure to asbestos, arsenic, chromium, nickel, beryllium, silica, or diesel exhaust
• Previous radiation therapy to the chest
• Air pollution
• A family history of lung cancer or inherited susceptibility
• Certain chronic lung diseases
• Increasing age

Risk factors change population-level probability; they do not mean that a particular person will develop cancer. Lung cancer can also occur without a known risk factor.

• Low-dose computed tomography (LDCT) is the screening method supported by evidence for people who meet defined high-risk criteria. Age, smoking exposure, and years since quitting must follow the current guideline for the user's country or region.
• Chest radiography and sputum cytology should not be presented as substitutes for evidence-based LDCT screening.
• Prevention priorities include never smoking, quitting as early as possible, avoiding secondhand smoke, testing homes for radon where relevant, and reducing occupational exposure to carcinogens.
• Stopping smoking can provide health benefits at any age.

Diagnosis is discussed within the Overview, Screening, Staging, and Biomarkers sections above for this cancer type. Specific tests depend on presentation, site, and pathology.

NSCLC is usually staged with the TNM system. T describes the primary tumor, N describes regional lymph nodes, and M describes distant metastasis. These categories are combined into stages I through IV.

SCLC is often described clinically as limited-stage or extensive-stage disease, although TNM staging can also be used.

Tumor grade describes how abnormal the cells appear and how actively they divide, but histologic type, TNM stage, and molecular characteristics often have greater influence on treatment selection.

Clinical stage is estimated before surgery; pathologic stage may be refined after examination of surgically removed tissue.

Lung cancer develops after cells accumulate genetic and epigenetic changes that disrupt normal controls on growth, survival, and DNA repair. Common oncogenic drivers in lung adenocarcinoma include alterations in EGFR, ALK, ROS1, KRAS, BRAF, MET, RET, ERBB2/HER2, and NTRK. Squamous cancers have a different molecular landscape and are strongly associated with tobacco-related DNA damage.

SCLC commonly shows neuroendocrine features and disruption of TP53 and RB1 pathways. Tumor microenvironment, immune evasion, angiogenesis, and the evolution of resistant subclones all influence progression and treatment response.

• EGFR sensitizing and selected uncommon mutations
• ALK, ROS1, RET, and NTRK fusions
• BRAF V600E
• KRAS G12C
• MET exon 14 skipping
• ERBB2/HER2 activating mutations
• PD-L1 expression
• Broad tissue-based next-generation sequencing or plasma circulating tumor DNA testing when clinically appropriate

A negative result does not always prove that no driver alteration exists. Sample size, tumor content, prior treatment, and assay sensitivity can affect results.

• EGFR
  Epidermal Growth Factor Receptor
• PD-L1
  Programmed Death-Ligand 1
• KRAS
  Kirsten Rat Sarcoma viral oncogene

• Early-stage NSCLC: surgery is the main curative treatment for some patients. Stereotactic body radiation therapy may be used when surgery is not appropriate. Depending on stage, lymph nodes, margins, molecular findings, and PD-L1 status, chemotherapy, immunotherapy, or targeted therapy may be considered before or after surgery.
• Locally advanced NSCLC: concurrent or sequential chemoradiation is common. Some patients receive consolidation immunotherapy after definitive chemoradiation.
• Advanced NSCLC: a targetable driver alteration may lead to targeted therapy. Without an actionable alteration, treatment may include immunotherapy, chemotherapy, or a combination based on histology, PD-L1, symptoms, and overall health.
• SCLC: platinum-based chemotherapy plus etoposide is a common foundation. Extensive-stage disease often includes immunotherapy. Radiation may be used for the chest, brain, or symptom control.
• Palliative and supportive care can be introduced at any stage to reduce symptoms and support quality of life.

• Chemotherapy: cisplatin, carboplatin, pemetrexed, paclitaxel, albumin-bound paclitaxel, docetaxel, gemcitabine, and etoposide
• Immune checkpoint inhibitors: pembrolizumab, nivolumab, atezolizumab, durvalumab, and ipilimumab
• EGFR-directed therapy: osimertinib and other agents for specific EGFR alterations
• ALK-directed therapy: alectinib, lorlatinib, and other approved ALK inhibitors
• ROS1-directed therapy: entrectinib, repotrectinib, taletrectinib, and other regionally approved agents
• KRAS G12C-directed therapy: sotorasib or adagrasib in defined settings
• RET-directed therapy: selpercatinib or pralsetinib
• MET exon 14-directed therapy: capmatinib or tepotinib
• BRAF V600E: a BRAF inhibitor combined with a MEK inhibitor
• HER2/ERBB2-directed approaches: selected kinase inhibitors or antibody-drug conjugates, depending on mutation, prior treatment, and regulatory approval

• Osimertinib
  Irreversible EGFR tyrosine kinase inhibitor · Targeted therapy
• Pembrolizumab
  Anti–PD-1 humanized monoclonal antibody · Immunotherapy

• Surgery: pain, reduced pulmonary function, pneumonia, blood clots, and cardiopulmonary complications
• Radiation: fatigue, skin reaction, esophagitis, cough, and radiation pneumonitis
• Chemotherapy: nausea, hair loss, bone marrow suppression, infection, neuropathy, kidney injury, or hearing damage, depending on the regimen
• Immunotherapy: immune-related pneumonitis, colitis, hepatitis, thyroid or other endocrine disorders, and less common inflammation of other organs
• Targeted therapy: rash, diarrhea, liver abnormalities, interstitial lung disease, cardiac effects, or ocular effects, depending on the drug
• Supportive care may include antiemetics, nutrition, pain treatment, smoking-cessation support, pulmonary rehabilitation, oxygen when indicated, psychosocial care, and early palliative care.

Fever during treatment, sudden shortness of breath, chest pain, confusion, or major hemoptysis requires prompt medical assessment according to local guidance.

• Current research is moving immunotherapy into neoadjuvant, perioperative, and adjuvant treatment for resectable NSCLC.
• Circulating tumor DNA is being studied for molecular residual disease, recurrence risk, and treatment monitoring.
• More selective and brain-penetrant drugs are being developed for HER2, ROS1, MET, KRAS, and other molecular subtypes.
• SCLC research includes molecular subtyping, antibody-drug conjugates, and new immune combinations.
• Repeat tissue or liquid biopsy is being evaluated to define mechanisms of acquired resistance.
• Recent U.S. regulatory examples include FDA approval of taletrectinib for adults with locally advanced or metastatic ROS1-positive NSCLC on June 11, 2025, and accelerated approval of zongertinib for an expanded HER2/ERBB2-mutated non-squamous NSCLC indication on February 26, 2026. These are U.S.-specific decisions and do not establish approval in other regions.

• What is the exact histologic type of my lung cancer?
• What are my clinical and, if applicable, pathologic stages?
• Is there enough tissue for broad molecular testing and PD-L1 testing?
• Do I need brain MRI, PET/CT, or invasive mediastinal lymph-node assessment?
• Is the goal to cure the cancer, reduce recurrence risk, or control disease?
• Am I a candidate for surgery, radiation, targeted therapy, or immunotherapy?
• What benefits, risks, and alternatives apply to the proposed plan?
• Which symptoms should prompt an urgent call to the care team?
• Are there clinical trials relevant to my tumor subtype and stage?
• Would pulmonary rehabilitation, smoking-cessation support, or nutrition services help me?