1. Coughing
   Early-stage lung cancer patients may experience a persistent cough for 2 to 3 weeks, which does not improve with cough medication. If blood is present in the sputum, it is often a red flag that requires immediate medical attention for further examination.

2. Chest Pain
   Some lung cancer patients may experience chest pain accompanied by coughing. This is due to the growth of tumor tissue invading the pleura, nerves, or muscles. Intermittent or persistent pain may occur in the chest, back, or shoulders.

3. Persistent Low Fever
   Individuals with lung cancer may experience prolonged or intermittent fever due to inflammatory responses in the body from the tumor cells' "unlimited growth," or due to necrosis and infection of the tumor tissue. If fever does not respond to antipyretics or anti-inflammatory medications, further medical evaluation is warranted.

4. Hoarseness
   Hoarseness is another early symptom of lung cancer. If the tumor is located near the throat, it can invade the nerves controlling the vocal cords, leading to progressively worsening hoarseness. Unlike conditions such as pharyngitis or throat surgery, hoarseness caused by lung cancer does not improve with treatment and may worsen.

5. Chest Tightness and Shortness of Breath

6. Symptoms of chest tightness and shortness of breath become apparent when a mass compresses or obstructs the trachea or bronchi, and rest does not alleviate these feelings. Additionally, lung cancer can affect the pleura, causing fluid accumulation in the chest cavity, leading to worsening respiratory difficulties.

For many, the early symptoms of lung cancer can be easily overlooked, often mistaken for fatigue or stress-related issues. Therefore, it is crucial to understand these early signs of lung cancer and also to know how to prevent it.

High-Risk Groups for Early Screening

Individuals aged 50 and older who meet any of the following criteria should undergo early screening:

1. Smoking history of 20 pack-years or more, including former smokers who have quit for less than 15 years. (Note: Pack-years = number of packs smoked per day × years of smoking.)
2. Living with or working alongside smokers for 20 years or more.
3. Having chronic obstructive pulmonary disease (COPD).
4. A history of occupational exposure (to asbestos, radon, beryllium, chromium, cadmium, nickel, silica, coal dust, and soot) for at least 1 year.
5. Having a first-degree relative (parents, children, siblings) diagnosed with lung cancer.

Early Screening Methods for Lung Cancer

Low-dose spiral CT scans of the chest are currently the most effective method for lung cancer screening. This method can detect small lesions in the lungs that are 2-3 mm or larger, with low radiation exposure, making it safer for the body. It is recommended that individuals over 40 years old who are at high risk for lung cancer undergo regular low-dose spiral CT screening for early detection.