non-small cell lung carcinoma

non-small cell lung carcinoma
Name	Non-small cell lung carcinoma
Synonyms	NSCLC
Caption	Diagram of the human lungs
Field	Oncology, Pulmonology
Symptoms	Cough, hemoptysis, chest pain, dyspnea
Complications	Superior vena cava syndrome, Pancoast tumor, paraneoplastic syndrome
Risks	Tobacco smoking, radon, asbestos, air pollution
Diagnosis	Chest radiograph, CT scan, biopsy
Treatment	Surgery, radiation therapy, chemotherapy, immunotherapy, targeted therapy
Prognosis	Varies by stage; 5-year survival ~25%
Frequency	~85% of all lung cancer cases

non-small cell lung carcinoma is the most prevalent form of lung cancer, accounting for approximately 85% of all cases. It encompasses several distinct histological subtypes that share similar treatment approaches and prognoses, contrasting with the more aggressive small-cell lung carcinoma. The disease is a major cause of cancer-related mortality worldwide, with its management evolving rapidly due to advances in molecular biology and immuno-oncology.

Signs and symptoms

Early-stage disease is often asymptomatic, with many cases discovered incidentally during imaging for other conditions. Common presenting symptoms include a persistent cough, hemoptysis (coughing up blood), chest pain, and worsening dyspnea (shortness of breath). As the tumor progresses locally, it may cause hoarseness from involvement of the recurrent laryngeal nerve or lead to pleural effusion. Advanced disease can manifest with constitutional symptoms like weight loss and fatigue, or complications such as superior vena cava syndrome and Pancoast tumor syndromes affecting the brachial plexus. Paraneoplastic phenomena, like hypercalcemia from parathyroid hormone-related protein secretion or hypertrophic osteoarthropathy, are also associated.

Classification and subtypes

The World Health Organization classification system, updated in 2021, defines several major subtypes based on histological appearance under light microscopy. The most common is adenocarcinoma, which often arises in the lung periphery and is frequently associated with mutations in genes like EGFR and ALK. Squamous cell carcinoma typically originates in the central airways near the carina and is strongly linked to a history of tobacco smoking. Large-cell carcinoma is a less common, undifferentiated subtype that often presents as a large peripheral mass. Other rarer variants include pleomorphic carcinoma and sarcomatoid carcinoma, which have poorer prognoses. Accurate subtyping is critical for guiding molecular testing and selecting appropriate targeted therapy.

Causes and risk factors

The predominant cause is chronic exposure to carcinogens found in tobacco smoke, with the risk correlating strongly with pack-year history. Environmental exposures are also significant, including inhalation of radon gas, asbestos fibers (which can also cause mesothelioma), and various occupational agents like arsenic, chromium, and nickel. Outdoor air pollution, particularly particulate matter, is recognized as a contributing factor by agencies like the International Agency for Research on Cancer. Genetic predisposition plays a role, with certain polymorphisms in genes involved in carcinogen metabolism, such as those in the CYP1A1 family, increasing susceptibility. A history of chronic obstructive pulmonary disease or prior radiation therapy to the thorax also elevates risk.

Diagnosis

Initial evaluation often involves imaging, starting with a chest radiograph which may show a mass, atelectasis, or hilar enlargement. Definitive characterization requires a CT scan of the thorax and abdomen, which assesses tumor size, location, and involvement of mediastinal lymph nodes. Tissue diagnosis is obtained via biopsy, which can be performed through bronchoscopy, CT-guided needle biopsy, or procedures like endobronchial ultrasound. Pathological examination confirms the diagnosis and subtype. Positron emission tomography is used for staging to detect distant metastasis. Molecular testing of the tumor tissue for driver mutations in genes like EGFR, ALK, ROS1, BRAF, and KRAS, as well as for PD-L1 expression, is now a standard part of the diagnostic workup to inform therapy selection.

Treatment

Management is highly dependent on the stage at diagnosis, determined by the TNM staging system. For early-stage disease (Stages I and II), curative-intent surgery, such as lobectomy or segmentectomy, is the cornerstone, often followed by adjuvant chemotherapy. Radiation therapy, including stereotactic body radiotherapy, is an option for patients who are not surgical candidates. For locally advanced disease (Stage III), a multimodal approach combining chemotherapy and radiation therapy is standard, sometimes followed by consolidation immunotherapy with agents like durvalumab. For metastatic disease (Stage IV), treatment is primarily systemic. First-line therapy is guided by molecular markers, using tyrosine kinase inhibitors for tumors with EGFR or ALK alterations, or immunotherapy (e.g., pembrolizumab, nivolumab) often combined with chemotherapy for tumors expressing PD-L1.

Prognosis

Prognosis is directly tied to the stage of disease at diagnosis, with significantly better outcomes for localized tumors. The overall 5-year survival rate is approximately 25%, but this ranges from over 60% for Stage IA disease to less than 10% for Stage IV. The presence of specific molecular alterations, such as EGFR mutations, is generally associated with a more favorable response to targeted agents and improved survival compared to tumors without these drivers. Performance status, as measured by scales like the Eastern Cooperative Oncology Group system, is a strong independent prognostic factor. Despite advances, the disease frequently recurs, and research into mechanisms of therapy resistance, such as the T790M mutation in EGFR, is ongoing to improve long-term outcomes.

Category:Lung cancer Category:Carcinoma