Stages of Lung Cancer

Lung cancer is a serious health concern that develops when abnormal cells in the lungs grow and multiply uncontrollably. These cells can form tumours and, if left untreated, may spread to other body parts, a process known as metastasis. Lung cancer is broadly categorised into two main types: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC).

Accurate lung cancer staging is crucial for determining the extent of the disease and developing an effective treatment plan. The staging process considers the primary tumour size and location, the presence or absence of cancer in nearby lymph nodes, and whether the cancer has spread to other organs.

Early detection and proper staging can significantly improve a patient’s prognosis and survival rates. Understanding the different stages of lung cancer empowers patients and their families to make informed decisions about their care and treatment options.

Lung Cancer Staging: TNM Classification

Lung cancer staging is a critical process that helps oncologists determine the extent of the disease and develop an appropriate treatment plan. The most widely used staging system for lung cancer is the TNM classification, which takes into account three key factors:

• Tumour (T): This factor describes the size and extent of the primary tumour. The T category is assigned a number (T1-T4) based on the tumour size and whether it has invaded nearby structures, such as the chest wall or diaphragm. For example, a T1 tumour is smaller than 3 cm and has not grown into nearby tissues, while a T4 tumour is larger and has invaded other organs or caused additional tumours in the same lung.
• Lymph Nodes (N): This factor indicates whether the cancer has spread to nearby lymph nodes. The N category is assigned a number (N0-N3) based on the location and extent of lymph node involvement. N0 means no cancer is found in the lymph nodes, while N1, N2, and N3 indicate increasing levels of lymph node involvement. For instance, N1 refers to cancer in the lymph nodes within the lung or near the bronchus, while N3 indicates cancer in the lymph nodes on the opposite side of the chest or above the collarbone.
• Metastasis (M): This factor determines whether the cancer has spread (metastasised) to other body parts. The M category is assigned either M0 (no distant metastasis) or M1 (distant metastasis present). Common sites of lung cancer metastasis include the brain, bones, liver, and adrenal glands.

The combination of T, N, and M categories helps oncologists at Apollo Proton Cancer Centre assign an overall stage to the lung cancer, ranging from Stage 1 (early-stage, localised cancer) to Stage 4 (advanced, metastatic cancer).

Non-small Cell Lung Cancer Stages

NSCLC accounts for approximately 85% of all lung cancer cases and is divided into four main stages based on the TNM classification system. Understanding these stages is crucial for determining the most appropriate treatment options and predicting patient outcomes.

Stage 1 NSCLC:

In Stage 1 NSCLC, the cancer is localised within the lung and has not spread to nearby lymph nodes (N0). This stage is further subdivided based on tumour size:

• Stage 1A: Tumors are less than 3 cm in size (T1a or T1b).
• Stage 1B: Tumors are between 3 cm and 4 cm (T2a).

Patients with Stage 1 NSCLC generally have the best prognosis, with 5-year survival rates ranging from 68% to 92%. Treatment options typically include surgical resection (lobectomy or segmentectomy) and, in some cases, adjuvant chemotherapy.

Stage 2 NSCLC:

In Stage 2 NSCLC, the cancer has grown larger or has spread to nearby lymph nodes. This stage is subdivided into:

• Stage 2A: Tumors are between 4 cm and 5 cm (T2b) with no lymph node involvement (N0), or tumours are less than 5 cm (T1a, T1b, or T2a) with involvement of nearby lymph nodes (N1).
• Stage 2B: Tumors are larger than 5 cm (T3) with no lymph node involvement (N0), or tumours are less than 5 cm (T2b) with involvement of nearby lymph nodes (N1).

Treatment for Stage 2 NSCLC typically involves surgical resection followed by adjuvant chemotherapy. In some cases, neoadjuvant chemotherapy or radiation therapy may be used to shrink the tumour before surgery. The 5-year survival rates for Stage 2A and 2B NSCLC range from 53% to 60%.

Stage 3 NSCLC:

In Stage 3 NSCLC, the cancer has spread to lymph nodes in the chest or other nearby structures. This stage is subdivided into:

• Stage 3A: Cancer has spread to lymph nodes on the same side of the chest as the primary tumour (N2), or the tumour has grown into nearby structures such as the chest wall, diaphragm, or mediastinum (T4).
• Stage 3B: Cancer has spread to lymph nodes on the opposite side of the chest (contralateral mediastinal) or above the collarbone (supraclavicular) (N3).

Treatment for Stage 3 NSCLC often involves a combination of chemotherapy, radiation therapy, and surgery. Depending on the tumour molecular characteristics, proton therapy may also be used. The 5-year survival rates for Stage 3A and 3B NSCLC range from 36% to 41%.

Stage 4 NSCLC:

In Stage 4 NSCLC, the cancer has metastasised to other parts of the body, such as the brain, bones, liver, or adrenal glands. Treatment for Stage 4 NSCLC typically focuses on systemic therapies such as chemotherapy, targeted therapy, or immunotherapy to control the cancer and improve quality of life. In some cases, local treatments such as radiation therapy or surgery may be used to alleviate symptoms or treat oligometastatic disease. The 5-year survival rate for Stage 4 NSCLC is approximately 10%.

Small Cell Lung Cancer Stages

SCLC is an aggressive form of lung cancer that accounts for about 15% of all lung cancer cases. Unlike NSCLC, SCLC is typically classified into two stages:

• Limited-stage SCLC: In Limited-Stage SCLC, the cancer is confined to one lung, nearby lymph nodes, and the area between the lungs (mediastinum). Treatment usually involves a combination of chemotherapy and radiation therapy. In some cases, prophylactic cranial irradiation (PCI) may be used to prevent brain metastases. The median survival for Limited-Stage SCLC is 15-20 months, with a 5-year survival rate of 20-25%.
• Extensive-Stage SCLC: In Extensive Stage SCLC, the cancer has spread to the other lung, lymph nodes on the opposite side of the chest, or other body parts, such as the brain, bones, or liver. Treatment typically involves systemic chemotherapy and, in some cases, immunotherapy. Radiation therapy may be used for palliation of symptoms or PCI. The median survival for Extensive-stage SCLC is 8-13 months, with a 5-year survival rate of less than 5%.

Conclusion

Accurate staging of lung cancer using the TNM classification system is essential for determining the most appropriate treatment options and predicting patient outcomes. By understanding the characteristics of each stage and also by using molecular tests, healthcare professionals can develop personalised treatment plans that optimise survival and quality of life for patients with NSCLC and SCLC.