What is Lung Cancer?
Lung cancer is a type of cancer that occurs due to the uncontrolled growth and multiplication of cells in the lungs. The primary function of the lungs is to take in oxygen necessary for the body's vital functions and to remove carbon dioxide produced during this process. Cancerous cells that proliferate uncontrollably grow in their environment and spread to surrounding tissues, causing damage.
It is the most diagnosed and the leading cause of death from cancer both globally and in Turkey. It accounts for about 19.4% of all cancer-related deaths, which is higher than the combined number of patients lost annually to breast, colon, and prostate cancer.
Lung cancer is generally categorized into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).
- Small Cell Lung Cancer (SCLC): SCLC accounts for approximately 15% of lung cancers. It tends to spread rapidly and often progresses more aggressively. However, it shows a better response to chemotherapy and radiation therapy.
- Non-Small Cell Lung Cancer (NSCLC): NSCLC constitutes around 85% of all lung cancers. It can progress without showing any symptoms.
Stage I and stage II NSCLC are considered early stages. However, since it often progresses without symptoms, most diagnosed patients are in stage III or stage IV.
Lung Cancer Types
Lung cancer can be classified into various types based on the structure and characteristics of the cancer cells. Some types include:
- Squamous cell carcinoma
- Large cell carcinoma
- Adenosquamous carcinoma
Lung Cancer Causes
The primary cause of lung cancer is cigarette smoking due to carcinogenic substances found in cigarette smoke. However, lung cancer can also occur in non-smokers. Apart from smoking, passive smoking, genetic factors, aging, air pollution, occupational exposure, and radiation exposure are contributing factors to lung cancer.
- Smoking: Smoking is the fundamental risk factor for lung cancer. The number of cigarettes smoked per day, duration of smoking, early age of starting smoking, depth of inhalation, and tar content increase the risk of developing cancer. There are over 4000 chemicals and more than 70 carcinogenic substances found in cigarette smoke. Long-term smokers are at 20 to 30 times higher risk compared to non-smokers. The use of 'light' cigarettes hasn't been proven to reduce cancer risk. Cigar smokers have a 3 times higher risk, and pipe users have an 8 times higher risk.
- Passive smoking: Approximately 17% of individuals diagnosed with lung cancer without a history of smoking are believed to have been exposed to smoke during their youth or childhood.
- Occupational exposure: Occupational exposure is responsible for about 5 to 10% of lung cancers. Asbestos exposure is the most known, but other occupational carcinogens include arsenic, chromium, formaldehyde, silica, heavy metals, and polycyclic aromatic hydrocarbons.
- Radiation exposure: Exposure to radiation through radiotherapy, atomic bombs, radon gas, and imaging tests increases the risk of lung cancer. The level and duration of exposure correlate with increased risk.
- Air pollution: A cohort analysis involving 300,000 individuals in nine European countries revealed that air pollution increases the risk of lung cancer. It's estimated that 1 to 3.6% of diagnosed lung cancers in Europe are related to air pollution.
- Alcohol: Alcohol consumption can weaken the immune system, reducing the body's ability to control cancer cells. This can increase the overall risk of cancer, though this effect is not specifically limited to lung cancer.
- Genetic factors: Genetic predisposition is also a significant risk factor for lung cancer. Individuals with a family history of lung cancer have twice the risk of developing it.
- Aging: Aging is a fundamental risk factor for many cancers. As individuals age, the risk of developing cancer increases.
Lung Cancer Symptoms
Lung cancer progresses silently and often shows symptoms in advanced stages. Persistent cough is the primary lung cancer symptom, followed by shortness of breath, chest pain, and coughing up blood. Compression or involvement of the vocal cord nerve can cause hoarseness. Phrenic nerve involvement may lead to diaphragm paralysis. Tumors located in the upper right lobe can cause swelling and redness in the neck and face due to compression on the superior vena cava. Tumors in the apex of the lung can cause Pancoast syndrome, leading to shoulder pain, weakness in the arm, and Horner's syndrome (drooping eyelid, smaller pupil, and decreased sweating on the same side of the face). Approximately 30% of diagnosed lung cancer patients can develop pleural effusion (fluid buildup in the lungs). Additionally, other general symptoms seen in many other cancer types, such as loss of appetite, weight loss, and fatigue, can also be symptoms of lung cancer.
Consulting a healthcare professional is crucial if any of the following symptoms are experienced:
- Chest pain or discomfort
- Persistent or changing chronic cough
- Difficulty breathing
- Coughing up blood
- Recurrent pneumonia or bronchitis
- Loss of appetite
- Unexplained weight loss
- Excessive fatigue
- Difficulty swallowing
- Swelling in the neck and face
Lung Cancer Diagnosed
Lung cancer diagnosis typically involves a patient's medical history, physical examination, complete blood count, and laboratory tests, followed by imaging and interventional procedures. Sputum cytology, which involves examining mucus samples taken from the lungs under a microscope, is a simple and cost-effective diagnostic method, particularly preferred for centrally located tumors.
Radiological diagnostic methods used for lung cancer diagnosis include:
- Chest X-ray: This is one of the initial methods used for diagnosing lung cancer. However, if the X-ray doesn't provide a definite answer, a computed tomography (CT) scan may be required.
- Chest CT scan: It's essential for evaluating suspicious or known lung masses and provides a more detailed view of lesions detected on an X-ray. It assists in staging cancer radiologically and provides information before other interventional procedures for diagnosis.
- Positron emission tomography (PET): It's the most accurate and sensitive imaging method for distinguishing between benign and malignant tumors. In lung cancer, it's highly effective in detecting mediastinal and hilar lymph node involvement and regional or distant metastases (except brain metastases).
Interventional diagnostic methods used for lung cancer include:
- Thoracentesis: This involves using a special needle to extract fluid from the space between the chest wall and lungs, which is then examined under a microscope for cancer cells.
- Fiberoptic bronchoscopy (FOB): It enables a detailed view of the trachea and bronchi to take biopsies, collect cytological and bacteriological material. Endobronchial lesions, external pressure, and exophytic submucosal lesions can be observed. Sampling methods like bronchoalveolar lavage, brushing, transbronchial fine needle aspiration (TBNA) can be used to obtain samples depending on the lesion's nature.
- Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA): In international guidelines, EBUS is recommended as the first-choice method for mediastinal staging in lung cancer. It's an effective, safe, repeatable, and minimally invasive method.
- Transthoracic fine needle aspiration/biopsy (TTNA/TTNB): This method is used for diagnosing peripherally located tumors. It is more effective in tumors inaccessible by FOB, and in such cases, a transthoracic approach with CT or ultrasound guidance is more beneficial.
- Thoracic surgical procedures: Surgical interventions might be necessary when sufficient material cannot be obtained through other procedures.
Lung Cancer Stages
Staging lung cancer is primarily based on imaging tests, bronchoscopy, biopsy, and other medical test results. The spread of cancer in the body occurs through a process called metastasis, where cancer cells break away from the original tumor, enter the bloodstream or lymphatic system, and spread to other areas or directly invade tissues and organs. Lung cancer most commonly metastasizes to lymph nodes, brain, liver, bones, adrenal glands, pleura, and other parts of the lungs.
The staging of non-small cell lung cancer (NSCLC) is determined as follows:
Stage I: The tumor is only in a small part of the lung and has not spread to any lymph nodes.
Stage II: The disease has spread to nearby lymph nodes or has skipped to the pleura surrounding the chest, diaphragm, lung, or heart.
Stage III: The tumor has spread to the mediastinum (the space between the lungs) or to the lymph nodes here, or there is involvement of the pleura, chest wall, or diaphragm with lymph node spread.
Stage IV: The tumor has spread to distant organs or the other lung, or there's fluid buildup between the lung or heart linings.
Small cell lung cancer (SCLC) is staged as "limited disease" or "extensive disease":
Limited disease: Cancer is present on only one side of the chest, in a part of the lung, and in adjacent lymph nodes.
Extensive disease: Cancer has spread to the other side of the lung or other parts of the body.
Recently, the staging system used for NSCLC has been proposed to be used in staging SCLC as well.
Lung Cancer Treatment
The treatment of lung cancer depends on the cell type, tumor stage, molecular characteristics, and the patient's overall condition. Patients with stage I and stage II can be treated with complete surgical resection if there are no contraindications (inability to use medication or medical products). For non-surgical patients, conventional or stereotactic radiotherapy can be considered. In locally advanced stages, chemoradiotherapy is used, and for advanced stages, chemotherapy, supportive care, targeted therapy, or immunotherapy are applied.
In recent years, targeted treatment methods have been developed for advanced lung cancer. These involve identifying genetic changes (EGFR, ALK, k-RAS, etc.) in cancerous tissue samples taken for diagnosis and directly using drugs that target these changes. Percutaneous thermal ablation methods can be tried in advanced NSCLC.
Additionally, in cases of tumors blocking the airways (trachea or major bronchi), methods such as laser therapy, photodynamic therapy, electrocautery, cryoablation, and placement of an airway stent can be used to relieve the obstruction. These treatment options can be used post-surgery, radiotherapy, or chemotherapy for palliation. The primary goal of managing advanced-stage SCLC is to maintain quality of life, minimize treatment complications, and extend survival.
How Can Lung Cancer Be Prevented?
- Avoiding smoking and exposure to cigarette smoke: Smoking is the greatest risk factor for lung cancer. The risk of lung cancer also increases in passive smokers. Thus, preventing smoking initiation and cessation for smokers are crucial in preventing lung cancer.
- Avoiding alcohol consumption: Alcohol consumption can increase the risk of lung cancer and other cancers.
- Protecting oneself from radiation: Unless necessary, exposure to radiation should be minimized. Those exposed to radiation in their professions should take appropriate protective measures.
- Avoiding toxic gases and chemicals: It's important to avoid inhaling toxic substances such as asbestos fibers, radon, and benzene. Those exposed to such materials in their professions should use protective gear like professional respiratory masks.
- Avoiding air pollution and breathing clean air: Pay attention to the air quality in the area where you live and try to choose clean air environments whenever possible.
- Adopting healthy lifestyle habits: Maintaining a balanced diet, maintaining ideal weight, regular sleep, regular exercise, and healthy lifestyle habits not only promote overall body health but also positively impact lung health.