Understanding Lung Cancer: Statistics, Symptoms, Stages, and Treatment Pathways

Understanding Lung Cancer: Statistics, Symptoms, Stages, and Treatment Pathways

Cancer is a disease marked by abnormal cell behavior and DNA mutations within the nucleus, resulting in uncontrolled cell growth and division. Beyond forming tumors through unfettered proliferation, cancer cells can invade adjacent organs, infiltrate the lymphatic vessels, and spread to nearby lymph nodes. They may also penetrate blood vessels and enter the bloodstream. At this point, cancer cells can disseminate throughout the body, including the lungs, liver, brain, and bones. At these new sites, the malignant cells continue to multiply, forming tumors that disrupt the function of the affected organs.

Lung Cancer Statistics: Global and Thai Perspectives

In 2022, the global cancer burden reached 20 million newly diagnosed cases. Of these, lung cancer accounted for 2.5 million cases, making it the most common form of cancer worldwide.

In 2021, lung cancer ranked as the sixth leading cause of death globally, following heart disease, COVID-19, stroke, chronic obstructive pulmonary disease (COPD), and lower respiratory tract infections.

In the United States, cancer is the second leading cause of death, surpassed only by ischemic heart disease, with lung cancer the leading cause of cancer-related deaths.
In Thailand, according to national cancer statistics published every three years, approximately 180,000 new cancer cases were diagnosed in 2022. By 2045, this number will trend upward by 50%. Alarmingly, nearly 40% of lung cancer cases in Thailand are at an advanced stage when first diagnosed, where treatment tends to be less effective and mortality rates are significantly higher.

Smoking: A Leading Cause of Lung Cancer

Lung cancer is due to genetic mutations in the DNA of lung cells, primarily due to two main factors:

1. External causes include smoking (active smoker) and secondhand smoke exposure (passive smoker). Prolonged smoking can lead to chronic irritation of the lung epithelium. Over time, the damage becomes irreparable and malignant. In addition to smoking, exposure to air pollution and inhalation of airborne chemical contaminants can also contribute to lung cancer.
2. Internal causes include somatic mutations or spontaneous changes within the DNA of lung cells. Under normal conditions, genes in the DNA regulate cell division, growth, and programmed cell death at a set rate to maintain a balanced cell population. However, accidents can occasionally occur during this intricate process, resulting in mutations and proliferation of abnormal cells (cancer cells). These cells divide rapidly from one cell to two, two to four, four to eight, and so on, eventually forming a sizable mass. This tumor can cause symptoms and initiate the process of invasion and metastasis.

Recognizing the Symptoms of Lung Cancer

The symptoms of lung cancer vary depending on the tumor’s location, size, adjacent organs, and stage of metastasis. Early manifestations often include:

• Coughing, as the tumor is a foreign body irritating the airway tissue.
• Hemoptysis occurs when the tumor damages nearby blood vessels.
• Shortness of breath occurs when a tumor grows large enough to obstruct the airway.
• Chest pain from tumor compression on the surrounding nerves or chest wall.
• Post-obstructive pneumonitis.
• Loss of appetite.
• Unintentional weight loss.
• Hoarseness can develop when an enlarging tumor or metastatic lymph node compresses the recurrent laryngeal nerve of the vocal cords.
• Difficulty swallowing occurs when the tumor or nearby lymph nodes press on the esophagus.

In addition, the symptoms that prompt patients to seek medical attention may, in some cases, arise from organs to which the cancer has already spread (distant metastasis), such as the lungs, bones, or brain.

How is Lung Cancer Diagnosed?

Since lung cancer treatment depends on the stage of the disease, a thorough diagnostic evaluation is essential. The process typically begins with a detailed medical history and symptom review, followed by a physical examination, blood tests, and imaging tests such as chest X-rays, CT scans, MRI, and whole-body PET/CT scans. A biopsy is necessary to confirm the diagnosis pathologically and identify the cancer type. Lung cancer is classifiable into two main types: Small Cell Lung Cancer (SCLC) and Non-Small Cell Lung Cancer (NSCLC). Identifying the cancer type can help determine the prognosis.
Approximately 80–85% of lung cancer cases fall under the NSCLC category. This group is categorizable into subtypes of adenocarcinoma (which encompasses several sub-subtypes not discussed here), squamous cell carcinoma, and large cell carcinoma (named for the appearance of its large, abnormal cells). Molecular testing identifies genetic mutations and biomarkers for personalized medicine.

Stages of Lung Cancer

The TNM staging system is the standard framework used to determine the stages of lung cancer. It evaluates three key components:

• T = Tumor
• N = Lymph Nodes
• M = Metastasis

The TNM classification system includes detailed criteria, but for ease of understanding among the public, lung cancer staging can be broadly summarized as follows:

• Stage 0: Occult (Hidden) Cancer: No visible tumor is present, but cancer cells are present in the sputum or bronchial washing.
• Stage I: The tumor is no more than 3 centimeters in diameter and has not spread to lymph nodes or other organs.
• Stage II: The tumor is more than 3 centimeters but less than 7 centimeters in size and remains confined to the lung without evidence of metastasis.
• Stage III: The tumor measures more than 5 centimeters but does not exceed 7 centimeters and may have spread to nearby lymph nodes or involve two tumors in the same lobe of the lung, but has not metastasized to distant organs.
• Stage IV: The cancer has spread to other parts of the lung, pleural effusion, pericardial effusion, or distant organs such as the liver, brain, bones, or even the opposite lung (e.g., from the left to the right lung or vice versa). This stage signifies hematogenous spread.

What Is the Most Effective Treatment for Lung Cancer?

The most effective treatment for lung cancer depends on the stage of the disease. In the early stages, e.g., Stage I and II, surgical resection is often the treatment of choice. The surgery involves removing the tumor along with affected lymph nodes, if feasible. However, patients who are not suitable candidates for surgery, due to advanced age, impaired pulmonary function, or severe comorbidities, such as heart disease, neurological disorders, or uncontrolled diabetes, may not safely tolerate the procedure. In such cases, radiation therapy, either alone or in combination with chemotherapy, is often considered an alternative treatment approach.

In Stage III, when surgical resection is not feasible, treatment typically involves a multimodal approach that includes chemotherapy and/or targeted therapy and immunotherapy (Immuno-Oncology) with radiation therapy. Treatment may begin with systemic therapy (neoadjuvant), followed by radiation, or both modalities may be administered concurrently (concurrent chemoradiation). If the tumor shows a favorable response, surgical removal of the residual mass may be considered, based on the assessment of the multidisciplinary medical team. 

In Stage IV disease, treatment is primarily systemic, involving chemotherapy, targeted therapy, and immunotherapy, as mentioned previously. Radiation therapy in this stage is for patients with bone pain caused by skeletal metastases to alleviate the pain and prevent pathological fractures, and in cases where cancer has spread to the brain where systemic therapies may not be sufficient, or for those with hemoptysis (coughing up blood) to shrink the tumor and halt active bleeding.

Lung Cancer Treatment Requires a Team of Multidisciplinary Specialists

Lung cancer treatment requires collaboration among various medical specialties, involving:

• A pulmonologist.
• A diagnostic radiologist assesses the extent and stage of the disease through imaging tests such as chest X-rays, CT scans, MRI, and PET/CT scans.
• A pathologist who examines tissue samples collected via bronchoscopy performed by the pulmonologist.
• If the tumor is located peripherally beyond the reach of bronchoscopy, an interventional radiologist can perform a CT-guided biopsy.

Once lung cancer is confirmed pathologically, a multidisciplinary team comprising a thoracic surgeon, a medical oncologist specializing in chemotherapy, targeted therapy, and immunotherapy, and a radiation oncologist will convene to formulate an individualized treatment plan.

How Long Do Lung Cancer Patients Live?

The prognosis for lung cancer depends on the stage of the disease, the patient’s overall health, the type of lung cancer - small cell lung cancer (SCLC) is typically more aggressive than non-small cell lung cancer (NSCLC), which progresses more slowly - and the chosen treatment approach. According to data from the SEER (Surveillance, Epidemiology, and End Results) database, the 5-year survival rates based on cancer stage and type are as follows:

MedPark Hospital is a state-of-the-art, comprehensive cancer center with teams of specialists dedicated to lung cancer care. Our leading pulmonologists provide consultations and recommend appropriate screening tests for high-risk individuals, such as long-term smokers and those exposed to hazardous chemicals in occupational settings. For these patients, annual low-dose chest CT scans are advisable for early detection. The multidisciplinary team at MedPark includes specialists in diagnostic radiology, pathology, thoracic surgery, medical oncology (including chemotherapy, targeted therapy, and immuno-oncology), nuclear medicine, radiation oncology, and other healthcare professionals specializing in cancer care. With advanced medical technologies and cutting-edge equipment, MedPark is committed to delivering precise, personalized treatment and supporting patients in achieving the best possible outcomes and quality of life throughout their cancer journey.