What Is Lung Cancer?

Lung cancer is a serious disease caused by the uncontrolled growth of cells in lung tissue. It most commonly develops as a result of long-term exposure to risk factors such as cigarette smoking, air pollution, asbestos, cancer is one of the most common types of cancer worldwide and can progress rapidly if not detected early. When diagnosed at an early stage, it may be treatable; however, treatment options and success rates decrease significantly in advanced stages.

What Are the Symptoms of Lung Cancer?

Symptoms of lung cancer usually appear as the disease progresses. In the early stages, there are often no noticeable signs or symptoms. The most common symptoms include:

• A persistent cough that worsens over time

• Coughing up blood (hemoptysis)

• Hoarseness

• Difficulty swallowing

• Loss of appetite

• Sudden and unexplained weight loss

Stage 0 Lung Cancer Symptoms

Stage 0 lung cancer is the earliest stage, in which cancer cells are confined to the inner lining of the lung. At this stage, there are usually no obvious symptoms, and the disease is often detected incidentally during routine screenings. Although symptoms may not be present, abnormal cancer cells can be observed in lung tissue. Imaging typically shows that the cancer has not spread.

Stage 1 Lung Cancer Symptoms

At stage 1, the tumor remains confined to the lung and has not spread to other organs. Symptoms are usually mild and may include cough, shortness of breath, or chest pain. At this stage, the cancer can often be surgically removed, and treatment success rates are high. Imaging studies show that the cancerous tissue is limited to a specific area.

Stage 2 Lung Cancer Symptoms

In stage 2, cancer cells begin to spread to deeper lung tissues and may reach nearby lymph nodes. Symptoms such as cough, bloody sputum, chest pain, and fatigue become more common. Treatment options at this stage may include surgery, chemotherapy, and radiotherapy. Imaging typically reveals tumor enlargement and possible lymph node involvement.

Stage 3 Lung Cancer Symptoms

At stage 3, cancer spreads beyond the lung to surrounding tissues and lymph nodes. Common symptoms include persistent cough, severe chest pain, difficulty swallowing, weight loss, and fatigue. Treatment becomes more complex and often involves a combination of surgery, chemotherapy, and radiotherapy. Imaging shows extensive involvement of lung tissue and spread to adjacent structures.

Stage 4 (Advanced Stage) Lung Cancer Symptoms

Stage 4 is the most advanced stage of lung cancer, characterized by metastasis to other organs. Common symptoms include severe shortness of breath, constant fatigue, bone pain, headaches, loss of appetite, and significant weight loss. At this stage, treatment focuses primarily on improving quality of life rather than curing the disease. Imaging shows widespread cancer involvement beyond the lungs.

What Causes Lung Cancer?

The most significant cause of lung cancer is cigarette smoking, although the disease can also occur in individuals who have never smoked. Smoking is responsible for more than 85% of all lung cancer cases.

Studies show that individuals who smoke more than 25 cigarettes per day have a 25-fold higher risk of developing lung cancer compared to non-smokers. Smoking is also a major cause of other cancers, such as esophageal and oral cancers.

Passive smoking also increases lung cancer risk. Women whose spouses smoke have been shown to have a 25% higher risk of developing lung cancer compared to those not exposed.

Another important risk factor is asbestos exposure. Asbestos is a fibrous mineral resistant to heat and wear, known for its carcinogenic properties. Although once widely used for insulation, exposure during asbestos removal continues to pose serious health risks.

Types of Lung Cancer

Cancer that originates in the lungs and spreads to surrounding tissues and organs is called primary lung cancer. Cancer that starts elsewhere in the body and spreads to the lungs is known as secondary lung cancer.

Primary lung cancers are divided into two main types:

• Small Cell Lung Cancer (SCLC):
Accounts for approximately 12% of cases. It is strongly associated with smoking and tends to spread very rapidly.

• Non-Small Cell Lung Cancer (NSCLC):
Represents about 88% of lung cancer cases. These cancers generally grow and spread more slowly and include three main subtypes:

    • Adenocarcinoma

    • Squamous cell carcinoma

    • Large cell carcinoma

These subtypes are grouped together because they behave similarly and respond to treatment in comparable ways.

Why Does Lung Cancer Develop?

Although the exact cause of lung cancer is not fully understood, several factors increase the risk:

• Smoking and Passive Smoking:
Smoking increases lung cancer risk by approximately 20 times, while passive smoking increases the risk by 20–30%.

• Radiation Exposure:
Exposure to ionizing radiation due to occupational exposure, radiation therapy, or nuclear incidents.

• Air Pollution:
Prolonged exposure to severe air pollution increases lung cancer risk.

• Radon Gas Exposure:
Radon is a naturally occurring radioactive gas that can accumulate in homes and buildings.

• Chronic Obstructive Pulmonary Disease (COPD):
Individuals with COPD have a higher risk of developing cancer.

• Family History:
A family history of lung cancer increases individual risk.

How Is Lung Cancer Diagnosed?

Individuals in high-risk groups may consider annual lung cancer screening with low-dose computed tomography (LDCT). Screening is generally recommended for healthy individuals aged 55 years and older with a long history of heavy smoking.

If symptoms suggestive of lung cancer are present, doctors may request imaging studies such as chest X-rays or CT scans. In cases of productive cough, sputum samples may be examined in the laboratory.

A biopsy, involving removal of abnormal tissue for examination, may be performed to confirm the diagnosis. Once lung cancer is diagnosed, its type and stage are determined, and an appropriate treatment plan is developed.

How Long Does It Take for Lung Cancer to Develop?

Lung cancer may develop slowly or rapidly. In many cases, it takes 5 to 10 years from the onset of abnormal cell growth until the cancer becomes clinically apparent. For this reason, lung cancer may remain asymptomatic for many years and is often diagnosed at an advanced stage. Regular screening and early detection are critical for improving treatment outcomes.