Lung Cancer

Lung Cancer: Causes, Symptoms, Diagnosis, and Treatment

Lung cancer is a disease that affects the lungs and causes abnormal cells to grow uncontrollably in lung tissue. It is one of the most common cancers worldwide and a leading cause of cancer death. Understanding the causes, risk factors, symptoms, diagnosis, and treatment options for lung cancer is important for early detection and improving survival rates.

What is Lung Cancer?

Lung cancer begins when cells in the lung mutate and grow out of control, forming a tumor. These abnormal lung cancer cells continue multiplying, eventually forming a mass or lump. Lung tumors cause problems by invading and damaging nearby tissues and organs and spreading throughout the body.

Cancers that begin in the lungs are divided into two major types:

• Small cell lung cancer (SCLC)- More aggressive cancer that spreads faster. Accounts for about 10-15% of lung cancers.
• Non-small cell lung cancer (NSCLC)- Most common type, accounting for 80-85% of lung cancer cases. Three main subtypes: adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.

Other less common lung cancers include carcinoid tumors and cancers that spread to the lungs from other sites, like breast, kidney, or colon cancer.

Lung cancer that has not spread beyond the lungs is called localized or early-stage lung cancer. If the cancer has spread to lymph nodes or other organs, it is referred to as advanced or metastatic lung cancer. Finding lung cancer in earlier stages before metastasis leads to better prognosis.

What Causes Lung Cancer?

The exact causes of lung cancer are not fully understood, but some key risk factors have been identified:

Smoking

Smoking is by far the leading risk factor, accounting for 80-90% of lung cancer cases. The longer a person smokes and the more cigarettes smoked per day, the greater their lung cancer risk. Smoking causes lung cell damage and inflammation which can lead to DNA mutations and cancer growth. Quitting smoking at any age lowers lung cancer risk compared to those who continue smoking.

Secondhand Smoke

Exposure to secondhand tobacco smoke also elevates lung cancer risk in nonsmokers. Secondhand smoke contains the same cancer-causing substances and chemicals as inhaled smoke. Workplace exposure to secondhand smoke is an important preventable cause of lung cancer.

Radon Gas

Radon is a radioactive gas naturally released by rocks and soil that can accumulate in houses and buildings at dangerous levels. Breathing in radon over time increases lung cancer risk, especially in smokers. Radon is the second leading cause of lung cancer after smoking.

Other Risk Factors

• Family history- Genetic factors and having a close relative with lung cancer raises risk.
• Carcinogens- Exposure to asbestos, arsenic, diesel exhaust, silica, chromium, nickel, and tar increases lung cancer risk, especially among smokers.
• Radiation therapy- Prior radiation treatment to the lungs or chest can cause lung cancer years later.
• Air pollution- Prolonged exposure to indoor and outdoor air pollution may slightly elevate lung cancer risk.
• Diet- A diet low in fruits and vegetables may also contribute to a small increase in lung cancer risk.

Lung Cancer Symptoms

In its earliest stages, lung cancer usually does not cause any symptoms. As lung tumors grow, they may begin causing the following common signs and symptoms:

• Chronic cough that gets worse or does not go away
• Coughing up blood or rust-colored spit or phlegm
• Shortness of breath, wheezing, or chest tightness
• Persistent infections like bronchitis or pneumonia
• Chest or shoulder pain, sometimes worse with deep breathing
• Losing weight and appetite loss for no known reason
• Hoarseness or changing voice
• Swelling or pain in the face or neck
• Feeling weak or constantly tired and fatigued

Lung cancer symptoms may vary depending on the size and location of tumors. People with early lung cancer tend not to feel sick or have symptoms, so getting lung cancer screenings is vital. If you have any chronic respiratory symptoms or think you may be at high risk, see a doctor.

Diagnosing Lung Cancer

If lung cancer is suspected based on risk factors or symptoms, diagnostic tests will be done to confirm diagnosis and determine the tumor size, location, if it has spread, and overall stage. Early accurate diagnosis is critical to proper lung cancer treatment and survival. Common diagnostic methods include:

Imaging Tests

• Chest X-ray- Often the first test, can detect tumors but may miss smaller ones.
• CT scan- More sensitive than x-rays, provides 3D images of lungs.
• PET scan- Uses radioactive tracer to identify cancer tissues.
• MRI scan- Provides detailed lung tumor imaging using magnetic fields. Can check for cancer spread.
• Bone scan- Checks if cancer has spread to bones. Radioactive material is injected that accumulates in diseased bone areas.

Tissue Sampling

• Sputum cytology- Microscopic examination of coughed up mucus samples for cancer cells.
• Needle biopsy- Using CT scan to guide needle, sample cells from tumor or suspicious lymph nodes.
• Bronchoscopy- Insert tubular lighted instrument down throat to examine airways. Can take biopsy samples.
• Mediastinoscopy- Visual exam of lymph node region between lungs and take lymph node biopsy through small incision.
• Thoracoscopy- Use tube with camera to examine space between lungs and chest. Samples can be taken.

Molecular Testing

Examining lung tumor's biomarkers and genes provides additional information for targeted therapies. Testing identifies if tumors contain gene mutations or arrangements that can influence treatment plans.

Lung Cancer Stages

Once diagnosis is confirmed, more imaging and biopsies are done to determine the stage of the lung cancer, which indicates size, location, and spread. The stages of lung cancer are:

Stage I

Cancer remains in lung and has not spread to lymph nodes. Overall 5-year survival is 50%.

Stage II

The tumor is larger or spread to nearby lymph nodes but not distant organs. Survival is 30%.

Stage III

Cancer has spread to lymph nodes and surrounding chest structures but not other organs. Or tumor has spread into chest wall or diaphragm. Survival is 15-20%.

Stage IV

Cancer has metastasized to distant lymph nodes or organs like liver, bones, brain. This is advanced lung cancer with 5% 5-year survival.

Early detection of stages I and II lung cancer leads to better prognosis and survival. Unfortunately, only 16% of lung cancers are diagnosed at these localized stages.

Treating Lung Cancer

Lung cancer treatment plans are tailored for each patient depending on the cancer's stage, location, size, person's overall health, and genetic markers. Common lung cancer treatments include:

Surgery

• Removing tumors and nearby lymph nodes through:
  • Segmentectomy- Smaller sections of lung removed
  • Lobectomy- Entire lobe with tumor removed
  • Pneumonectomy- Entire lung removed

Radiation Therapy

• High energy x-ray beams aimed at tumors to destroy cancer cells and shrink tumors.

Chemotherapy

• Using anti-cancer drugs injected into a vein or taken orally to kill rapidly dividing cancer cells. Often combined with radiation as first line treatment.

Targeted Therapy

• Oral medicines that specifically target cancer cells with less harm to healthy cells. Examples are epidermal growth factor receptor (EGFR) inhibitors and anaplastic lymphoma kinase (ALK) inhibitors.

Immunotherapy

• Drugs that help immune system detect and destroy cancer cells. checkpoint inhibitor drugs remove brakes on the immune system.

Photodynamic Therapy

• Involves injecting a light-sensitive drug that accumulates in cancer cells, then activating it with laser light directed at tumor.

Minimally Invasive Procedures

• Destruction of lung tumors using laser, microwave, or radiofrequency ablation. Used for early stage lung cancers.

Managing Symptoms and Supportive Care

• To improve quality of life, treatments can help control pain, breathing problems, fatigue, appetite issues, cough, and other symptoms caused by lung cancer or side effects of treatment.

Combinations of surgery, chemo, radiation, and targeted therapies are commonly used for lung cancer treatment. The outcomes and survival rates are highly dependent on how early lung cancer is detected and the stage at diagnosis.

Lung Cancer Prevention

While some risk factors for lung cancer cannot be avoided, taking preventive measures can significantly lower your chances of getting lung cancer:

• Don't smoke- If you smoke, quitting is the most important thing you can do to prevent lung cancer. It's never too late to quit.
• Avoid secondhand smoke
• Test your home for radon- Take measures to lower high radon levels with improved ventilation.
• Limit exposure to known lung cancer carcinogens
• Eat a healthy diet- Eat plenty of fruits and vegetables which are linked to lower lung cancer risk.
• Get lung cancer screening- Annual screenings for those at high risk can detect lung cancer early when it's most treatable.
• Get recommended vaccinations- Immunizations against flu and pneumonia may help protect against lung infections that raise risk.
• Exercise regularly- Physical activity is associated with lower occurrence of lung cancer.

Raising awareness, more screening, and reducing exposure to risk factors will all contribute to lowering lung cancer cases and deaths worldwide.

(Disclaimer: Above article is only for informational purposes. This is not for Medicinal or treatment purposes. This information might not be accurate. Please consult respective expert/ professional to know more.)