lung cancer

lung cancer
Field	Oncology, Pulmonology

lung cancer is a malignant tumor characterized by uncontrolled cell growth in tissues of the lung. It is a leading cause of cancer mortality globally, with the vast majority of cases linked to long-term tobacco smoking. The disease often presents with non-specific symptoms, leading to frequent diagnosis at advanced stages, though screening programs using low-dose computed tomography are improving early detection in high-risk populations.

Signs and symptoms

Early stages are frequently asymptomatic, but as the disease progresses, common manifestations include a persistent cough, hemoptysis, chest pain, and dyspnea. Systemic symptoms such as unintentional weight loss, fatigue, and fever may also occur. Tumors located at the lung apex can cause Pancoast syndrome, involving shoulder pain and Horner's syndrome. Paraneoplastic syndromes are associated with certain types, such as syndrome of inappropriate antidiuretic hormone secretion linked to small-cell lung carcinoma or hypercalcemia from parathyroid hormone-related protein secretion.

Causes and risk factors

The predominant cause is prolonged exposure to carcinogens found in tobacco smoke, with risk strongly correlated to pack-year history. Other significant risk factors include exposure to radon gas, asbestos, air pollution, and certain industrial agents like arsenic and chromium. Genetic predisposition plays a role, with familial clustering observed and specific susceptibility loci identified through studies like those from the International Agency for Research on Cancer. Pre-existing lung diseases, such as chronic obstructive pulmonary disease and pulmonary fibrosis, also elevate risk.

Diagnosis

Initial assessment often involves chest radiography, but definitive diagnosis typically requires computed tomography and positron emission tomography for localization and staging. Histopathology from a biopsy obtained via bronchoscopy, CT-guided needle biopsy, or mediastinoscopy is essential for confirming the diagnosis and classifying the tumor type. Sputum cytology can be used but has lower sensitivity. Molecular testing for genetic mutations in genes like EGFR, ALK, and KRAS is now standard to guide targeted therapy.

Types and staging

The two main broad categories are small-cell lung carcinoma and non-small-cell lung carcinoma, with the latter comprising subtypes including adenocarcinoma, squamous-cell carcinoma, and large-cell carcinoma. Staging follows the TNM staging system established by the American Joint Committee on Cancer and the Union for International Cancer Control. For non-small-cell lung carcinoma, stages range from I (localized) to IV (metastatic), while small-cell lung carcinoma is often classified using the Veterans Administration Lung Study Group system as either limited or extensive stage.

Treatment

Management is multidisciplinary and depends heavily on the cancer type, stage, and molecular profile. Surgical options include lobectomy, segmentectomy, or pneumonectomy, often performed with video-assisted thoracoscopic surgery. Radiation therapy, including advanced techniques like stereotactic body radiotherapy, is used for definitive treatment or palliation. Systemic therapy includes platinum-based chemotherapy, immunotherapy agents targeting PD-1 or PD-L1 like pembrolizumab, and tyrosine kinase inhibitors for tumors with specific driver mutations. Treatment plans are frequently guided by trials from cooperative groups like the Eastern Cooperative Oncology Group.

Prognosis and epidemiology

Overall prognosis remains poor, with a five-year survival rate heavily dependent on stage at diagnosis, ranging from high for localized disease to very low for metastatic disease. It is the most common cause of cancer death worldwide, with high incidence rates in regions like Eastern Europe and East Asia. Major public health initiatives, including the Framework Convention on Tobacco Control and screening recommendations from the United States Preventive Services Task Force, aim to reduce the global burden. Research efforts continue through organizations like the National Cancer Institute and Cancer Research UK.

Category:Respiratory diseases Category:Cancer types