Lung Cancer is a malignant disease arising in tissues of the lungs or associated respiratory structures and is a heterogeneous group of diseases rather than one uniform tumour. The two broad pathological categories are non-small cell lung cancer and small cell lung cancer, with non-small cell disease accounting for roughly 85% of cases. Lung cancers differ in histology, molecular alterations, growth rate, metastatic behaviour and treatment sensitivity. In 2024, IARC estimated almost 2.65 million new lung cancer cases worldwide and more than 1.8 million deaths, making lung cancer the most commonly diagnosed cancer globally and the leading cause of cancer death.
Tobacco smoking is the principal preventable cause of Lung Cancer, although smoking status does not fully determine individual risk and lung cancer can occur in people who have never smoked. Other established or important risk factors include second-hand smoke, radon, outdoor and household air pollution, occupational exposure to asbestos, silica and diesel exhaust, and certain chronic lung conditions. Genetic susceptibility also contributes to risk. WHO reports that smoking accounts for a majority of preventable lung cancer cases, while IARC identifies smoking as responsible for approximately 85% of all cases and also highlights environmental and occupational exposures.
Symptoms of Lung Cancer can include persistent cough, chest pain, breathlessness, haemoptysis, fatigue, unexplained weight loss and recurrent respiratory infections. Early disease may produce few or nonspecific symptoms, which contributes to delayed diagnosis. Diagnostic assessment can involve chest imaging, particularly computed tomography, bronchoscopy, biopsy and histopathological examination. Molecular testing has become increasingly important in non-small cell lung cancer because certain genomic alterations can determine eligibility for targeted therapies. Diagnosis therefore combines anatomical imaging, tissue pathology and, when appropriate, molecular characterisation.
Lung Cancer staging assesses the extent of the primary tumour, regional lymph-node involvement and distant metastases. Accurate staging is essential because localised disease can have fundamentally different treatment objectives and options from metastatic disease. Depending on tumour type and stage, treatment can include surgery, radiation therapy, chemotherapy, targeted therapy and immunotherapy, used individually or in combinations. For non-small cell disease, molecular testing may identify alterations that make particular targeted treatments appropriate. For small cell lung cancer, treatment strategies differ because of its distinct biology, typical growth pattern and sensitivity to systemic treatment and radiation.
Targeted treatment has become particularly important in molecularly defined Lung Cancer. Alterations involving pathways or genes such as EGFR, ALK, ROS1, BRAF, RET, MET, NTRK, KRAS and other biomarkers can identify subgroups for which specific systemic treatments may be considered, depending on the exact alteration and approved indication. NCI describes EGFR-directed treatment as an example of precision medicine in a subset of lung cancers with activating EGFR alterations. This illustrates why molecular testing can be clinically consequential: two tumours with similar histology and stage can have substantially different therapeutic options because their molecular drivers differ.
Prevention is a major component of Lung Cancer control because a large proportion of cases are attributable to modifiable or avoidable exposures. Tobacco control, smoking cessation, smoke-free environments, reduction of occupational exposures and mitigation of relevant air-pollution risks can reduce incidence. Radon mitigation can also be important in areas where exposure is significant. Prevention is complemented by early detection, but screening is not intended for every person indiscriminately. WHO describes screening of defined high-risk individuals, particularly heavy current or former smokers, as capable of reducing lung-cancer mortality when implemented with appropriate quality assurance and follow-up.
Advanced Lung Cancer may involve spread to lymph nodes, bones, liver, brain, adrenal glands or other organs. Treatment of metastatic disease depends on histology, molecular profile, distribution of metastases, overall health, previous therapy and individual preferences. Systemic treatments such as chemotherapy, targeted therapy and immunotherapy are central for many patients, while radiation or surgery may be used for selected local complications or symptomatic metastases. WHO emphasises that treatment goals in metastatic disease include prolonging survival and alleviating symptoms while maintaining quality of life. Clinical trials are also an important route for evaluating new therapies and treatment strategies.
Lung Cancer has particular significance in public health because its burden combines a high global mortality rate with substantial preventability. IARC estimates that tobacco smoking is responsible for approximately 85% of cases, but the remaining burden demonstrates that lung cancer cannot be treated as exclusively a smoking-related disease. Never-smokers can develop lung cancer through other environmental, occupational or biological mechanisms, and they may also develop tumours with actionable molecular alterations. Effective control therefore requires both population-level prevention and sophisticated diagnostic and therapeutic services. The disease illustrates the interaction between epidemiology, environmental exposure, molecular genetics, precision treatment, early detection and health-system capacity.
