Lung cancer is a malignant neoplasm arising from the respiratory epithelium and is broadly classified into non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). It remains a leading cause of cancer mortality worldwide due to frequently late presentation, aggressive biology in certain subtypes, and metastatic potential. Clinically, lung cancer may present with cough, hemoptysis, dyspnea, chest pain, recurrent pneumonia, or systemic manifestations such as weight loss and fatigue; however, asymptomatic cases are increasingly detected via imaging.
From a pathobiological standpoint, carcinogenesis involves cumulative genetic and epigenetic alterations driven by chronic exposure to carcinogens and replication stress. Tobacco smoke is the dominant risk factor, containing polycyclic aromatic hydrocarbons and nitrosamines that induce DNA adducts and mutations. In NSCLC, common oncogenic drivers include EGFR mutations, ALK rearrangements, ROS1 rearrangements, KRAS mutations, and MET alterations; these molecular events promote uncontrolled proliferation and survival signaling through pathways such as MAPK/ERK and PI3K/AKT. Tumor microenvironment effects—including immune evasion, angiogenesis, and fibroblast-mediated remodeling—contribute to progression. SCLC is characterized by neuroendocrine differentiation, rapid growth, and frequent inactivation of TP53 and RB1, leading to high proliferative rates.
Risk assessment integrates both exposure history and host factors. Tobacco exposure (including pack-years), secondhand smoke, occupational exposures (e.g., asbestos, silica, diesel exhaust), and radon gas increase risk. Additional contributors include prior radiation to the chest and genetic predisposition syndromes. Screening with low-dose computed tomography (LDCT) is recommended for eligible individuals with substantial smoking histories, aiming to detect disease at earlier, more curable stages.
Diagnosis typically begins with imaging abnormalities on chest radiography or CT, followed by tissue confirmation. A diagnostic pathway may include CT, PET-CT for metabolic staging, and brain imaging for selected clinical scenarios. Tissue acquisition can be accomplished through bronchoscopy with transbronchial biopsy, endobronchial ultrasound-guided sampling, CT-guided percutaneous biopsy, or surgical biopsy. Cytology and histology determine subtype, while molecular testing is essential for NSCLC because it directly affects treatment selection. For example, actionable alterations may guide targeted therapy using EGFR, ALK, ROS1, or other inhibitors, whereas SCLC relies more heavily on chemotherapy and immunotherapy.
Staging is based on TNM criteria and determines prognosis and therapeutic strategy. Localized disease may be treated with curative intent using surgical resection and/or radiotherapy. Stage III disease often involves multimodality therapy (chemoradiation plus consolidation or additional systemic therapy, depending on molecular context and clinical factors). Metastatic disease is managed with systemic approaches, including chemotherapy, targeted agents, immunotherapy, and, in some cases, palliative radiation for symptom control.
Treatment selection is increasingly personalized. NSCLC management can incorporate immune checkpoint inhibitors that target PD-1/PD-L1 and CTLA-4, especially in tumors with PD-L1 expression or after appropriate molecular profiling. Targeted therapies exploit specific driver mutations and can yield substantial response rates and progression-free survival improvements compared with conventional chemotherapy. SCLC is generally treated with platinum-based chemotherapy combined with etoposide, and immunotherapy is frequently incorporated in modern regimens; the goal is disease control in a biologically fast-growing malignancy.
Supportive care is a critical component of lung cancer treatment. Symptom-directed interventions include management of cough and dyspnea, control of pain, treatment of cancer-related cachexia when present, nutritional support, and psychosocial care. Rehabilitation and palliative services can improve quality of life and align care with patient goals. Monitoring includes surveillance imaging schedules for treated patients and evaluation for treatment-related toxicities such as immune-related adverse events (e.g., pneumonitis, colitis, endocrinopathies) with immunotherapy.
Prognosis varies widely by stage, histology, molecular profile, and performance status. Early-stage disease has significantly better outcomes after curative therapy, while advanced metastatic disease requires ongoing systemic control. Smoking cessation is strongly recommended for all patients and can improve treatment tolerance and long-term survival.
In summary, lung cancer is a complex, genetically driven respiratory malignancy with major subdivisions (NSCLC and SCLC) that differ in biology, diagnostic testing priorities, and therapeutic approaches. Evidence-based care depends on timely detection, accurate histologic and molecular characterization, appropriate staging, and integration of surgery, radiotherapy, systemic therapy, and comprehensive supportive services. Source: @ENERGY
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— @ENERGY May 1, 2026
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