Lung Cancer: Types, Causes, Symptoms, Complications, Prevention

Lung cancer definition

Lung cancer is a kind of cancer that begins in the lungs, the organs which help in breathing. It occurs when abnormal cells in the lung tissue grow uncontrollably and form tumors. Lung cancer is one of the most common and dangerous types of cancer, affecting both smokers and non-smokers alike.

It is often asymptomatic in its early stages and is typically discovered only at advanced stages, which makes it challenging to treat successfully. Consequently, there is a growing emphasis on early lung cancer screening. Therefore, it is important to seek medical help early to avoid serious health effects.

Lung Cancer Meaning

The term "lung" is derived from the Old English word "lunge," which refers to the organ responsible for respiration. The word "cancer" is derived from the Greek word "karkinos," which means a crab, representing the shape of the tumours. The term symbolizes the disease's ability to spread to different body parts, like a crab's legs extending outward.

Lung cancer prevalence

Lung cancer prevalence worldwide

Globally, lung cancer is one of the most often diagnosed cancers. As per the World Health Organization (WHO), in 2020, there were approximately 22 lakh new lung cancer cases, making it the second most prevalent cancer globally after breast cancer. This type of cancer is considered the leading cause of cancer-related fatalities, with an estimated 18 lakh deaths occurring annually.

Lung cancer prevalence in India

In India, lung cancer rates are on the rise, with an estimated 78,000 new cases reported in 2020. The incidence of lung cancer in India is high and varies by state. In 2021, the incidence of lung cancer in India was 67,795 cases, which was 5.9% of all cancer cases. It has become a major public health concern, particularly in urban areas, due to rising tobacco use and air pollution. The disease is also diagnosed more frequently in men than in women, reflecting the higher incidence of smoking.

Types of lung cancer

The major types of lung cancers are grouped anatomically by the structure from which they arise. These classifications are significant for the choice of treatment and prognosis. 

Lung cancer classification: Different categories of lung cancer include:

1. Non-Small Cell Lung Cancer (NSCLC): 
2. Adenocarcinoma
3. Squamous Cell Carcinoma
4. Large Cell Carcinoma
5. Small cell lung cancer (SCLC)
6. Carcinoid Tumors

Non-small cell lung cancer (NSCLC)

It accounts for 80% to 85% of lung cancer cases. Non-small cell lung cancer includes several subtypes, each of which has its own unique histological features. The most common subtypes are:

• Adenocarcinoma: The most common type of NSCLC, adenocarcinomas are lung cancers that develop from glandular cells. They are found more frequently in women and those who do not smoke. These tumors are often seen as masses in the lungs' outer sections and can sometimes secrete mucus.

• Squamous Cell Carcinoma: This cancer develops from squamous cells lining the airways. It is usually located in the centre of the lungs and has strong connections with smoking. These tumours often appear in the lungs as central masses with hollow spaces.

• Large Cell Carcinoma: This type is known for its large, undifferentiated cells and can occur in any part of the lung. It is generally a fast grower and spreader, making it hard to treat.

Small cell lung cancer (SCLC)

It accounts for about 10% to 15% of lung cancers. This is a highly aggressive type of lung cancer that begins in the neuroendocrine cells of the lungs. Like most forms of lung cancer, SCLC is significantly connected to smoking. Most SCLC patients usually have a history of smoking, which is the reason for concern, given the casual relationship between the two entities. SCLC is characterized by small, round cells with scant cytoplasm and a high nuclear-to-cytoplasmic ratio.

• Carcinoid Tumours: These are rare tumors that originate in the neuroendocrine cells of the lungs. They are slow growing by nature, account for fewer than lung tumours, and are usually less aggressive than other types.
  

Lung cancer causes

The exact cause of lung cancer remains relatively unclear, but there are several risk factors which can lead to it, including:

• Tobacco: Tobacco smoking is responsible for 85% of lung cancer cases, causing about 8 out of 10 cases of lung cancer in females and 9 out of 10 cases in males. The risk is high if the person smokes more cigarettes.

• Second-hand smoke: Second-hand smoke comes from the smoke of a burning cigarette and the smoke exhaled by a smoker. Breathing in second-hand smoke exposes individuals to cancer-causing agents, increasing the risk of related health conditions.

• Air pollution: As per some studies, living in areas with higher levels of air pollution can raises the risk of lung cancer.

• Exposure to chemicals: Being exposed to certain chemicals such as asbestos, arsenic, chromium, beryllium, nickel, soot, or tar in the workplace increases the chances of developing lung cancer. 

• Genetics: A family history of cancer can leads to mutations that can increase the chances of lung cancer, although these cases are rare. 

• Previous Lung Diseases: Other diseases, such as Chronic obstructive pulmonary disease (COPD) and even tuberculosis, can make a person more susceptible to lung cancer.

• HIV infection: The risk is higher if the person has HIV. People with HIV have higher smoking rates, making it unclear whether the increased risk is due to HIV infection or smoking.
  

Lung cancer symptoms

Since signs of lung cancer may not show up until the disease has progressed, lung cancer frequently goes undetected in its early stages. However, early diagnosis and treatment can be aided by identifying warning symptoms, including: 

• A persistent cough: It persists for an extended period and either worsens or does not improve. It might produce strange phlegm or blood. 

• Shortness of Breath: Breathing difficulties can occur during everyday routines, often because of tumour growth obstructing the airways.

• Chest discomfort: Patients with lung cancer experience sharp or dull pain or severe discomfort in the chest region that worsens with deep breathing, laughing, or coughing.

• Unexplained Weight Loss: Significant weight loss without dietary or exercise modifications frequently indicates cancer-related metabolic changes. 

• Fatigue: Patients experience continuous weakness or tiredness that interferes with routine activities, does not improve with rest, and affects daily activities.

• Hoarseness: A voice change resulting from nerve involvement or pressure on the vocal cords, making it sound strained or raspy.

• Haemoptysis, or coughing up blood: For those with lung cancer, haemoptysis occurs because of tumour growth within the lungs, damaging blood vessels and creating bleeding within the airways. This symptom is one of the leading indicators of lung cancer.

• Facial or neck swelling: The tumor pressing up against major veins can blocks blood flow, resulting in noticeable swelling.

Symptoms of lung cancer in females are generally similar to those in males, including persistent cough, chest pain, and shortness of breath.

Complications of lung cancer

Lung cancer complications can occur as the disease advances, spreads to other organs, or as a result of treatment side effects. The following lung cancer complications impact a person's general health and quality of life: 

• Breathing Problems: Lung tumours can block or narrow the airways, causing severe dyspnoea (breathing difficult) and decreased lung function.

• Pleural Effusion: Lung cancer can cause pleural effusion by spreading to the pleura, leading to increased fluid production due to inflammation or obstruction of lymphatic flow. 

• Metastatic lung cancer (Metastasis: cancer spread): Lung cancer commonly spreads to other organs, such as the brain, liver, or bones, leading to additional complications and symptoms.

• Respiratory Infections: Weakened lung function due to lung cancer makes patients more prone to recurrent infections, including pneumonia and bronchitis.

• Blood Clots: Lung cancer can cause blood clots in the lungs by triggering a hypercoagulable state and tumour-related vessel compression, leading to pulmonary embolism.

• Pain Management Issues: As the cancer progresses, it can cause severe pain, mainly if it spreads to the bones or nerves.

• Superior Vena Cava Syndrome: A tumour pressing on the superior vena cava (a major vein in the chest) can cause facial, neck, and upper body swelling.

• Psychological Impact: A lung cancer diagnosis can lead to mental and emotional health challenges such as anxiety, depression, and stress.
  

Lung cancer diagnosis

Early diagnosis of lung cancer is vital for effective treatment. Various methods are employed to confirm the diagnosis, including:



• Medical history and physical examination
• Blood Tests
• Imaging Tests
• Chest X-ray
• CT scan
• PET Scan
• Biopsy
• Bronchoscopy
• Endobronchial Ultrasound (EBUS)
• CT-guided Core biopsy
• Sputum Cytology
• Other tests
• Lung Function Test
• Mediastinoscopy
• Thoracoscopy
  

Lung cancer treatment

Lung cancer treatments vary based on the type, stage, and tumor location and the patient's overall health, including:

• Surgery (Lung cancer surgery)
• Radiation Therapy
• Chemotherapy (Lung cancer medications)
• Targeted Therapy
• Immunotherapy
• Palliative Care
  

Lung cancer prevention

While it may not be possible to prevent lung cancer completely, individuals can take steps to reduce their risk through lifestyle changes and by avoiding risk factors that contribute to its development. Here are some key preventive measures:



• Quitting smoking: It is the leading cause of lung cancer. The most effective way to reduce the risk of lung cancer is to quit smoking and avoid exposure to second-hand smoke.

• Minimizing the exposure to carcinogenic chemicals: Reducing exposure to workplace chemicals such as asbestos and radon gas. Ensuring proper ventilation and safety measures in high-risk environments can help to avoid exposure.

• Exercise Regularly: Physical activity improves lung function and overall health. Regularly exercising can help reduce inflammation and enhance immunity.

• Avoiding air pollution: Reducing exposure to outdoor and indoor pollutants like smoke and chemicals. Using air purifiers and maintaining clean indoor air quality can help to prevent air pollution.

• Maintaining a Healthy Diet: A diet rich in vegetables, fruits, and whole grains boosts immunity. Antioxidants in healthy foods may help protect against cancer cell formation.

• Vaccination: Chronic infections can lead to inflammation, increasing cancer risk. Protecting against infections through vaccination for flu and pneumonia can help prevent lung infections.

• Getting regular screenings: High-risk individuals should undergo regular lung cancer screenings. Early detection through low-dose CT scans can improve treatment outcomes.