What is Lung Cancer?

Lung cancer is a disease characterized by uncontrolled growth of cells in the lungs. Normally, cells divide only when needed and in a controlled manner. However, sometimes these cells undergo changes or mutations that cause them to multiply uncontrollably. This uncontrolled division leads to the formation of masses or tumors that interfere with normal lung function. These abnormal cells can also invade nearby tissues and spread to other parts of the body—a process known as metastasis. This is a simplified explanation; the actual process involves complex interactions between genetic and environmental factors. It is important to note that not all lung tumors are cancerous. Tumors can also be benign, meaning they do not spread to other parts of the body.

Lung cancer refers to malignant tumors that originate in the lungs, usually starting in the bronchi, bronchioles, or alveoli—structures responsible for air exchange. However, it is important to distinguish primary lung cancer from metastatic lung cancer. Primary lung cancer begins in the lungs, while metastatic lung cancer starts elsewhere in the body and later spreads to the lungs. In metastatic cases, the cancer is still named after its origin. For example, if breast cancer spreads to the lungs, it is still called breast cancer, but is described as having metastasized to the lungs.

Different Forms of Lung Cancer

Lung cancer is broadly divided into two main types: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC).

Non-small cell lung cancer (NSCLC) is the most common type, accounting for over 80% of all lung cancer cases. It includes several subtypes, the most common being adenocarcinoma and squamous cell carcinoma. Adenosquamous carcinoma and sarcomatoid carcinoma are rarer forms of NSCLC.

Small cell lung cancer (SCLC), on the other hand, tends to grow faster and is more challenging to treat than NSCLC. It often presents as a small lung tumor that has already spread to other parts of the body. Variants of SCLC include small cell carcinoma (also known as oat cell carcinoma) and mixed small cell carcinoma.

Cancer Incidence

In 2020, the global age-standardized incidence rate of lung cancer was 22.4 per 100,000 people. This means that approximately 22.4 individuals per 100,000 were diagnosed with lung cancer. It is important to recognize that this is an average, and actual incidence can vary significantly depending on factors such as geographic location, lifestyle, and genetic predisposition. Additionally, over 2.2 million new cases of lung cancer were reported worldwide in 2020, highlighting its major global health impact and high mortality.

Symptoms

Most lung cancers do not cause symptoms until they reach an advanced stage. However, recognizing early signs can lead to earlier diagnosis and more successful treatment. Although these symptoms are often caused by non-cancerous conditions, it is important to consult a doctor if they persist.

Common symptoms include:

Persistent or worsening cough

Coughing up blood or rust-colored sputum

Chest pain that worsens with deep breathing, coughing, or laughing

Hoarseness

Loss of appetite

Unexplained weight loss

Shortness of breath

Chronic fatigue

Recurrent infections such as bronchitis or pneumonia

Sudden wheezing

If lung cancer spreads, it may cause:

Bone pain, often in the back or hips

Neurological issues such as headaches, weakness or numbness in limbs, dizziness, balance problems, or seizures due to brain metastasis

Jaundice (yellowing of the skin and eyes) if the cancer spreads to the liver

Swollen lymph nodes in the neck or above the collarbone

Certain lung cancers can also cause syndromes characterized by specific groups of symptoms.

Causes

Lung cancer occurs when mutations in lung cells disrupt the mechanisms that regulate cell division and death, leading to uncontrolled growth. These mutations can result from various factors, with tobacco smoke being the most significant risk factor. Other contributors include exposure to radon, asbestos, certain metals, radiation, air pollution, and genetic predisposition. Aging and normal cell processes like apoptosis usually prevent such uncontrolled growth, but in cancer cells, these processes are disrupted, resulting in tumor formation and potential metastasis.

Risk Factors

Smoking: The leading cause, accounting for about 90% of lung cancers. This includes cigarettes, cigars, and pipes.

Secondhand smoke: Exposure also increases risk.

Radon exposure: A naturally occurring radioactive gas that can accumulate in homes.

Asbestos exposure: Common in mining, factories, shipyards, and insulation work.

Other carcinogens: Exposure to radioactive ores, arsenic, diesel exhaust, and certain chemicals.

Air pollution: Also a recognized risk factor.

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

Not everyone exposed to these factors will develop lung cancer, but they do increase the likelihood.

Diagnosis and Testing

Diagnosis involves several tests:

Chest X-ray: Can detect larger tumors (>1 cm).

CT scan: Uses X-ray beams to create cross-sectional images; can detect smaller tumors and assess lymph nodes.

PET scan: Used for staging after diagnosis.

Pulmonary function tests: Spirometry may be used to assess lung function.

Biopsy: If a tumor is suspected, a small tissue sample is taken. Types include bronchoscopy, CT-guided core biopsy, and endobronchial ultrasound.

Sputum cytology: Mucus from the lungs is examined under a microscope for abnormal cells.

These tests help confirm diagnosis, determine staging, and guide treatment planning.

Treatment

Traditional treatments:

Surgical resection: Involves removing the tumor surgically. However, it can be traumatic and carries high risks, with some deaths attributed to complications.

Radiation and chemotherapy: Can kill cancer cells but also damage normal cells, leading to side effects such as weakened immunity, low blood counts, hair loss, and vomiting. These may not be suitable for advanced-stage patients.

Newer minimally invasive options:

Interventional therapy: 1–2 mm incision to inject anti-cancer drugs directly into the tumor, with fewer side effects. Drug concentration is 2–8 times higher than systemic chemotherapy.

Cryotherapy: Reduces surgical risk and complications, with minimal bleeding and fast recovery. Can be repeated to prevent recurrence.

Microwave ablation: Can ablate tumors up to 6 cm in ~10 minutes, with high safety, low toxicity, and low recurrence.

Particle implantation (brachytherapy): Involves implanting ¹²⁵I seeds into the tumor, emitting γ-rays for 180 days with high precision and minimal invasiveness.

Integrated traditional Chinese and Western medicine: May help control tumors and prolong survival for patients unsuitable for chemo/radiotherapy.

Treatment plans should always be tailored to the individual.

Lung Cancer Staging：

Prognosis

Prognosis varies by type and stage. General 5-year relative survival rates:

Localized NSCLC: 65%

Regional NSCLC: 37%

Distant NSCLC: 9%

Localized SCLC: 30%

Regional SCLC: 18%

Distant SCLC: 3%

These are averages; individual outcomes depend on overall health, treatment response, and other factors. Always consult a healthcare provider for personalized information.

Caring for Lung Cancer Patients: Key Points for Caregivers

Caregivers play a vital role in providing medical, practical, and emotional support. Key responsibilities include:

Medical tasks:

Medication management

Managing side effects

Attending medical appointments

Coordinating with healthcare providers

Preparing emergency contacts

Assisting with personal and palliative care

Daily assistance:

Grocery shopping and meal preparation

Maintaining a clean living space

Transportation to appointments

Managing laundry and bills

Emotional support:

Being a supportive presence

Allowing expression of emotions

Respecting different emotional responses to cancer

Caregiver self-care:

Join support groups

Consider professional counseling

Stay active and maintain a healthy lifestyle

Balancing caregiving duties with personal well-being is essential to prevent burnout. The emotional burden and potential stigma associated with lung cancer make self-care and seeking support even more critical.