What Is Lung Cancer?
Lung cancer begins when abnormal cells in the lungs grow uncontrollably, forming tumours that can spread to other organs. It is the leading cause of cancer death globally, with more than 200,000 new US cases each year.
Types of Lung Cancer
Non-Small Cell Lung Cancer (NSCLC)
Non-small cell lung cancer (NSCLC) is the most common form and accounts for 80-85% of all cases. The main types of non-small cell lung cancer are: Adenocarcinoma. This is the second most common form of lung cancer, representing about 40% of cases. More common in non-smokers and arises in the outer part of the lung. Squamous cell carcinoma This accounts for about 25-30% of cases of NSCLC. More commonly associated with cigarettes and arises in the central airways. Large cell carcinoma: This accounts for about 10-15% of cases.
Small Cell Lung Cancer (SCLC)
Small cell lung cancer (SCLC) accounts for nearly 15-20% of cases and is largely caused by cigarette smoking. It progresses rapidly and 70% of patients are diagnosed with extensive-stage disease that has spread to locations beyond one lung.
Symptoms of Lung Cancer
Lung cancer is often silent in early stages. When symptoms do appear, they can resemble common respiratory illnesses:
- A persistent cough that does not improve over time
- Shortness of breath or increasing breathlessness
- Chest pain or discomfort, especially during breathing or coughing
- Coughing up blood (haemoptysis), even in small amounts
- Hoarseness or a change in voice.
- Unexplained weight loss or loss of appetite.
- Persistent fatigue.
- Wheezing or noisy breathing.
Additionally, advanced disease may result in eyelid drooping (Horner's syndrome), facial/neck swelling (superior vena cava syndrome), or shoulder pain (Pancoast tumor). Any persistent symptom needs to be evaluated right away.
Risk Factors and Causes
Smoking
About 80% of lung cancer deaths are caused due to smoking. Smoking cigars and pipe tobacco also pose an equal risk. The more you smoke, and the longer you smoke, the higher your risk.
Additional Important Risk Elements
* In the US, secondhand smoke causes about 7,300 non-smoker deaths annually.
* Indoor air pollution caused by radon gas - second most prevalent risk factor for noncommunicable diseases: A new study published in the journal Nature estimates that indoor air pollution caused by the build-up of radon gas in homes results in about 21,000 deaths annually in the United States.
The following is a list of exposures found in the workplace and for which research indicates that cancers are likely to be caused or associated with working with asbestos, arsenic, chromium, silica, nickel and diesel engine exhaust. The jobs with the greatest potential for exposure are in mining, shipbuilding and construction.
* Air pollution: prolonged exposure to PM2.5 is known to cause cancer.
Family history: a first-degree relative with lung cancer roughly doubles the risk
- Prior chest radiation: previous radiotherapy (for example breast cancer) increases risk in the treated field
Up to 20% of patients are never-smokers; EGFR, ALK, and ROS1 mutations are more common in this group.
Stages of Lung Cancer
NSCLC Staging (Stages I-IV)
- Stage I - tumour in the lung only; no lymph node or distant spread
- Stage II - larger tumour or spread to lymph nodes within the same lung
- Stage III - cancer has reached lymph nodes in the central chest or nearby structures
- Stage IV- spread to the other lung, pleural/pericardial fluid, or distant organs (brain, liver, adrenal glands)
SCLC Staging
SCLC is clinically described as limited stage (one lung and nearby lymph nodes; treatable with a single radiation field) or extensive stage (spread beyond one lung; ~70% of patients). It is also staged using the same I-IV system.
How Is Lung Cancer Diagnosed?
Diagnosis follows a structured pathway:
- Initial evaluation- history, examination, chest X-ray, blood tests
- Lung Cancer Screening Guideline Version 2.0 Recommendation
- Low-dose computed tomography (LDCT) Annual lung cancer screening with LDCT is recommended for asymptomatic adults at high risk for developing lung cancer, specifically those aged 50 years or older with at least 20 pack-years of smoking history.
- PET-CT- evaluates spread to lymph nodes or distant organs.
- Biopsy- the definitive step; performed via bronchoscopy, CT-guided needle, or surgery
- Endpoints
- Biomarker and PD-L1 testing The identification of specific mutations in DNA in a tumor such as EGFR, ALK, ROS1, KRAS G12C, BRAF, MET and RET are used to select appropriate therapies for a patient’s cancer.
Treatment Options for Lung Cancer
Treatment is determined by cancer type, stage, and biomarker profile:
- Surgery - It is the preferred treatment for early stage NSCLC. Surgical procedures include: Lobectomy: the removal of the affected lobe Pneumonectomy: the removal of the affected lung, often performed with VATS (Video Assisted Thoracoscopic Surgery) procedures in order to reduce recovery time and minimize scarring.
- 1st Line Treatment Chemotherapy -platinum-based regimens given before surgery, after surgery, with radiation or as primary treatment
Treatment options:
Radiation therapy - EBRT, SBRT and IMRT for curative and palliative applications.
Targeted therapy Oral targeted therapies are drugs that work by addressing specific genetic mutations, such as EGFR, ALK, KRAS G12C, MET, RET and BRAF V600E. They are more commonly used as a first or second line of treatment in non-small cell lung cancer (NSCLC) adenocarcinoma.
Immunotherapy - checkpoint inhibitors (pembrolizumab, nivolumab, atezolizumab, durvalumab) for patients with high PD-L1 expression or in combination with chemotherapy For extensive-stage SCLC, immunotherapy is now added to first-line chemotherapy.
Conclusion
Lung Cancer is a serious and often silent killer but understanding risk factors and the symptoms of Lung Cancer, as well as the benefits of screening, can save lives. New and innovative diagnostics and therapies that offer improved survival rates and quality of life are now available to Lung Cancer patients when diagnosis is made at an early stage.
Stopping smoking, reducing your exposure to air pollution and talking to your doctor if you have symptoms that persist are important measures for reducing your risk and improving your long-term health.
