Lung Cancer: Types and Risk Factors

• Lung cancer is a malignant tumor that starts in the lungs, typically in the cells lining the air passages
• It is the leading cause of cancer death worldwide

Types of Lung Cancer

• Non-Small Cell Lung Cancer (NSCLC) is the most common type, accounting for about 80-85% of all lung cancers
• NSCLC subtypes include adenocarcinoma, squamous cell carcinoma, and large cell carcinoma
• Small Cell Lung Cancer (SCLC) accounts for about 10-15% of lung cancers
• SCLC is more aggressive and tends to spread more rapidly than NSCLC

Risk Factors

• Smoking is the leading risk factor for lung cancer, with the risk increasing with the number of cigarettes smoked and the duration of smoking
• Exposure to secondhand smoke also increases the risk of lung cancer
• Radon gas is a naturally occurring radioactive gas that can accumulate in homes and increase the risk of lung cancer
• Asbestos exposure, particularly when combined with smoking, significantly increases the risk of lung cancer, leading to mesothelioma and lung cancer
• Other risk factors include air pollution, certain occupational exposures (such as arsenic, chromium, and nickel), previous radiation therapy to the chest, and a family history of lung cancer

Symptoms

• Lung cancer may not cause symptoms in its early stages
• Common symptoms include a persistent cough, coughing up blood (hemoptysis), chest pain, hoarseness, unexplained weight loss, loss of appetite, shortness of breath, and recurrent respiratory infections (such as pneumonia or bronchitis)
• Advanced lung cancer can cause bone pain, neurological symptoms (such as seizures or weakness) if the cancer spreads to the brain, and jaundice if the cancer spreads to the liver

Diagnosis

• Imaging tests such as chest X-rays and CT scans can help detect lung tumors
• Sputum cytology involves examining mucus coughed up from the lungs under a microscope to look for cancer cells
• Bronchoscopy involves inserting a thin, flexible tube with a camera into the airways to visualize the lungs and collect tissue samples
• Biopsy involves removing a small tissue sample from the lung for examination under a microscope
• Types of biopsies include needle biopsy, surgical biopsy (thoracotomy or VATS), and lymph node biopsy

Staging

• Staging helps determine the extent of the cancer and guide treatment decisions
• The TNM staging system is commonly used, where T describes the size and extent of the primary tumor, N describes whether the cancer has spread to nearby lymph nodes, and M describes whether the cancer has metastasized to distant organs
• NSCLC staging ranges from Stage I (early stage, localized) to Stage IV (advanced stage, distant metastasis)
• SCLC is typically staged as either limited stage (cancer is confined to one side of the chest and nearby lymph nodes) or extensive stage (cancer has spread beyond the chest or to distant organs)

Treatment

• Treatment options for lung cancer depend on the type and stage of cancer, as well as the patient's overall health
• Surgery may be an option for early-stage NSCLC, involving removal of the tumor and nearby lymph nodes
• Types of surgery include wedge resection (removal of a small section of the lung), lobectomy (removal of an entire lobe of the lung), and pneumonectomy (removal of an entire lung)
• Radiation therapy involves using high-energy rays to kill cancer cells and can be used as the main treatment, before surgery, or after surgery
• Chemotherapy involves using drugs to kill cancer cells and can be used alone or in combination with other treatments
• Targeted therapy involves using drugs that target specific molecules involved in cancer cell growth and can be effective for some NSCLCs with specific genetic mutations or protein abnormalities
• Immunotherapy involves using drugs that help the body's immune system recognize and attack cancer cells
• Immunotherapy drugs called checkpoint inhibitors (e.g., pembrolizumab, nivolumab) have shown significant benefits in some patients with advanced NSCLC
• Palliative care focuses on relieving symptoms and improving quality of life for patients with advanced lung cancer

Screening

• Screening for lung cancer is recommended for individuals at high risk, such as heavy smokers and those with a history of smoking
• Low-dose CT (LDCT) scans are used to screen for lung cancer
• Screening can help detect lung cancer at an earlier stage when it is more treatable
• Guidelines vary, but generally include annual LDCT screening for individuals aged 50-80 who have a 20 pack-year smoking history and currently smoke or have quit within the past 15 years

Prevention

• Quitting smoking is the most important way to prevent lung cancer
• Avoiding secondhand smoke and exposure to radon and asbestos can also reduce the risk
• A diet rich in fruits and vegetables may help lower the risk of lung cancer
• Regular exercise and maintaining a healthy weight are also recommended

Adenocarcinoma

• Adenocarcinoma is a subtype of NSCLC that begins in the mucus-producing gland cells of the lungs
• It is the most common type of lung cancer in non-smokers and women
• Adenocarcinoma often occurs in the outer regions of the lungs

Squamous Cell Carcinoma

• Squamous cell carcinoma is a subtype of NSCLC that arises from the squamous cells lining the airways
• It is strongly associated with smoking
• Squamous cell carcinoma typically occurs in the central part of the lungs

Large Cell Carcinoma

• Large cell carcinoma is a subtype of NSCLC that is a fast-growing cancer with large, abnormal cells
• It can occur anywhere in the lungs
• Large cell carcinoma tends to spread quickly

Small Cell Lung Cancer

• Small cell lung cancer (SCLC) is a highly aggressive type of lung cancer that is strongly associated with smoking
• It is characterized by small, oval-shaped cells
• SCLC typically starts in the central part of the lungs and spreads rapidly to other parts of the body
• SCLC is often treated with chemotherapy and radiation therapy

Mesothelioma

• Mesothelioma is a cancer that develops from the lining of the lungs, abdomen, or heart
• It is strongly associated with asbestos exposure
• Symptoms of mesothelioma include chest pain, shortness of breath, and fluid buildup in the chest or abdomen

Pleural Effusion

• Pleural effusion is the accumulation of fluid in the pleural space, the area between the lungs and the chest wall
• It can be caused by lung cancer, infections, heart failure, and other conditions
• Symptoms of pleural effusion include shortness of breath, chest pain, and cough
• Diagnosis involves chest X-ray, CT scan, and thoracentesis (removal of fluid from the pleural space for analysis)
• Treatment may involve draining the fluid, treating the underlying cause, or pleurodesis (sealing the pleural space to prevent fluid buildup)

Paraneoplastic Syndromes

• Paraneoplastic syndromes are conditions caused by substances produced by cancer cells that affect distant organs or tissues
• Common paraneoplastic syndromes in lung cancer include SIADH (syndrome of inappropriate antidiuretic hormone secretion), hypercalcemia (high calcium levels), and Cushing's syndrome (excess cortisol)
• Treatment involves managing the underlying cancer and addressing the specific paraneoplastic syndrome

Superior Vena Cava Syndrome

• Superior vena cava (SVC) syndrome occurs when the SVC, a major vein that carries blood from the upper body to the heart, is blocked or compressed by a tumor
• It can be caused by lung cancer, lymphoma, and other cancers
• Symptoms include swelling of the face, neck, and arms, shortness of breath, and cough
• Treatment may involve radiation therapy, chemotherapy, or placement of a stent in the SVC

Pancoast Tumors

• Pancoast tumors are lung cancers that occur in the apex (top) of the lung and can invade nearby structures such as the ribs, nerves, and blood vessels
• They can cause severe shoulder pain, Horner's syndrome (drooping eyelid, constricted pupil, and decreased sweating on one side of the face), and weakness or numbness in the arm and hand
• Treatment may involve surgery, radiation therapy, and chemotherapy

Targeted Therapies

• EGFR inhibitors (e.g., gefitinib, erlotinib, osimertinib) target the epidermal growth factor receptor (EGFR) protein, which is often mutated in NSCLC
• ALK inhibitors (e.g., crizotinib, alectinib, brigatinib) target the anaplastic lymphoma kinase (ALK) protein, which is rearranged in some NSCLCs
• BRAF inhibitors (e.g., vemurafenib, dabrafenib) target the BRAF protein, which is mutated in some NSCLCs
• ROS1 inhibitors (e.g., crizotinib, entrectinib) target the ROS1 protein, which is rearranged in some NSCLCs
• These targeted therapies are often used in patients with advanced NSCLC whose tumors have specific genetic mutations or protein abnormalities

Immunotherapies

• Checkpoint inhibitors (e.g., pembrolizumab, nivolumab, atezolizumab) block proteins such as PD-1 and PD-L1 that prevent the immune system from attacking cancer cells
• They can be used alone or in combination with chemotherapy
• Immunotherapy has shown significant benefits in some patients with advanced NSCLC, improving survival rates