Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. It originates in lung tissues and typically progresses slower than small cell lung cancer. Understanding NSCLC, its forms, and how it impacts the body is important for diagnosis and treatment.
Understanding Non-Small Cell Lung Cancer
Non-small cell lung cancer is categorized into subtypes based on how cancer cells appear under a microscope. This classification helps medical professionals understand the disease’s characteristics. NSCLC accounts for 80% to 85% of all lung cancer cases, making it the predominant form.
Small cell lung cancer (SCLC) cells appear small and round, and SCLC is generally more aggressive and spreads quickly. NSCLC cells are larger and less uniform under a microscope, distinguishing it from SCLC. This difference influences treatment strategies.
The three main subtypes of NSCLC are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Adenocarcinoma is the most common subtype (about 40% of NSCLC cases), often beginning in the outer lung parts within mucus-producing cells. It is also common in non-smokers. Squamous cell carcinoma, the second most prevalent, starts in flat cells lining the airways, typically in the central lungs, and is strongly linked to tobacco smoking. Large cell carcinoma is less common (10% to 15% of diagnoses), characterized by large, undifferentiated cells that can appear anywhere in the lung and often spread rapidly.
Recognizing Signs and Causes
Non-small cell lung cancer often presents with symptoms that can be mistaken for less severe conditions, especially in early stages. A persistent cough that worsens over time is a common indicator. Other symptoms include shortness of breath, chest pain or discomfort, and unexplained weight loss.
Individuals may also experience fatigue, hoarseness, loss of appetite, and coughing up mucus or blood. Recurring respiratory infections, such as pneumonia or bronchitis, can also be a sign. If the cancer has spread, symptoms like bone pain, headaches, or swelling in the face or neck veins may occur.
Smoking is the leading cause of NSCLC, responsible for 85% to 90% of all lung cancer cases. The risk correlates with the amount and duration of smoking. Secondhand smoke exposure significantly increases risk, accounting for over 7,300 lung cancer deaths annually.
Beyond tobacco, environmental and occupational exposures contribute to NSCLC. Radon exposure, a naturally occurring radioactive gas, is a cause, especially in non-smokers. Exposure to hazardous chemicals like asbestos, arsenic, chromium, beryllium, and nickel also elevates risk. Air pollution and a family history of lung cancer are additional factors.
Diagnosing and Staging NSCLC
Diagnosing non-small cell lung cancer involves tests to confirm cancer and determine its characteristics. Initial suspicion often arises from imaging tests like a chest X-ray, which can reveal unusual spots or masses. If an X-ray shows abnormalities, a computed tomography (CT) scan provides more detailed images of the lungs and surrounding structures.
Magnetic resonance imaging (MRI) may assess if a tumor has invaded the chest wall or diaphragm. A positron emission tomography (PET) scan identifies malignant tumor cells by detecting increased metabolic activity. While imaging can suggest cancer, a biopsy is required for a definitive diagnosis. During a biopsy, a tissue sample from the suspected tumor or lymph node is collected, often guided by CT or ultrasound, or through bronchoscopy. Pathologists then examine these samples under a microscope to identify cancer cells and determine the NSCLC type.
Staging NSCLC determines the cancer’s extent within the body. This information guides treatment planning and prognosis. The most widely used system is the TNM system, which assesses three factors: the size and extent of the primary tumor (T), whether cancer has spread to nearby lymph nodes (N), and if it has spread to distant parts of the body (M), known as metastasis.
Based on these factors, NSCLC is assigned a stage from 0 to IV. Stage 0 indicates abnormal cells confined to the airway’s top lining, without deeper spread or lymph node/distant site involvement. Stage I cancers are small and localized to the lung, without lymph node involvement. As the stage increases (Stage II, Stage III), it signifies larger tumors or spread to nearby tissues and lymph nodes. Stage IV, the most advanced stage, indicates metastasis to distant organs like the other lung, brain, bones, or liver. This system helps tailor treatment.
Treatment Approaches for NSCLC
Treatment for non-small cell lung cancer is individualized, with decisions made by a multidisciplinary team based on the cancer’s stage, subtype, patient health, and tumor’s genetic characteristics. A range of treatment modalities are available, often used alone or in combination.
Surgery is a primary treatment for early-stage NSCLC when the tumor is localized and can be removed. This may involve a lobectomy (removing an entire lung lobe), a segmentectomy (removing a portion of the lobe), or for very small tumors, a wedge resection (removing a small, wedge-shaped piece of lung). The goal is to remove all cancerous tissue and nearby lymph nodes to prevent recurrence.
Radiation therapy uses high-energy beams, such as X-rays, to destroy cancer cells or shrink tumors. It can be delivered externally (with a machine outside the body) or internally (by placing radioactive materials directly into or near the tumor). Radiation therapy may be used after surgery to eliminate remaining cancer cells, as a primary treatment for patients unable to undergo surgery, or to alleviate symptoms in advanced stages.
Chemotherapy uses powerful drugs to kill cancer cells throughout the body. These drugs can be administered intravenously or orally, interfering with cancer cells’ ability to grow and divide. Chemotherapy can be given before surgery to shrink tumors (neoadjuvant therapy), after surgery to destroy remaining cancer cells (adjuvant therapy), or as a primary treatment for advanced NSCLC, sometimes combined with radiation therapy.
Targeted therapy uses drugs designed to attack specific molecules within cancer cells involved in their growth and spread. This treatment is effective for NSCLC tumors with particular genetic mutations, such as changes in EGFR, ALK, BRAF, or KRAS genes. Before starting, molecular testing is performed on tumor tissue to identify these mutations. These drugs aim to stop cancer growth while minimizing harm to healthy cells, often leading to different side effects than traditional chemotherapy.
Immunotherapy harnesses the body’s own immune system to fight cancer. Cancer cells can sometimes evade detection, but immunotherapy drugs, particularly immune checkpoint inhibitors, help the immune system recognize and attack them. These drugs work by blocking “checkpoint” proteins on immune cells (like PD-1 or CTLA-4) or on cancer cells (like PD-L1), which normally prevent the immune system from attacking healthy cells. By blocking these checkpoints, the drugs unleash the immune response against the cancer. Immunotherapy can be used for various stages of NSCLC, sometimes as a first-line treatment or after other therapies.