The lung cancer staging process begins once a lung cancer diagnosis is confirmed. Beyond an initial computed tomography (CT or CAT) scan, your doctor will likely order a brain magnetic resonance imaging (MRI) scan to see if there is any evidence of disease in the braina common area of metastasisand a positron emission tomography (PET) scan to see whether the lung cancer has metastasized to your bones, adrenal glands, and/or liver.
Taken together, all of this information helps to stage your cancer, which can assist the physician in comprehending the depth of the cancer, establishing a prognosis, and ultimately optimizing a treatment plan moving forward. Lung cancer is generally classified into two basic classes, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). Furthermore, the staging process differs for each. Although some information on lung cancer staging classifications may seem 'dry' or somewhat mundane at times, it is pertinent information to keep you in the 'know' regarding disease progression.
Read MoreNon-Small Cell Lung Cancer (NSCLC)
NSCLC is the most ordinary classification of lung cancer, accounting for approximately 84% of all lung cancer diagnoses. There are three general subtypes of NSCLC: squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Adenocarcinoma, which accounts for about 40% of all NSCLC cases, is the single most common subtype of lung cancer. It is typically found along the outer perimeter of the lungs and tends to progress at a slower rate compared to other lung cancer types. Squamous cell carcinoma makes up about 30% of all NSCLC cases, and is the second most common subcategory of lung cancer. Squamous cells line the trachea and the bronchi of the lungs, which are exposed to air when we inhale and exhale. Because of this, squamous cells can be exposed to toxins, including smoke for cigarettes. It has been shown that the risk of obtaining squamous cell carcinoma is directly correlated with the cumulative number of cigarettes smoked over time. Squamous cell carcinoma typically manifests in the central portion of the lungs. Due to this central localization, symptoms are often exhibited earlier rather than later compared to other types of NSCLC. This will often lead to a quicker diagnosis and hopefully treatment.Large cell carcinoma is the rarest main classification and accounts for about only 15% of cases. Other less common subtypes of NSCLC include the following: carcinoid tumor, salivary gland carcinoma, pleomorphic, and carcinomas that remain unclassified. Procedures that are typically used in lung cancer staging of NSCLC include lymph node biopsy, anterior mediastinotomy, and mediastinoscopy.
TNM Classification of Tumors
The American Joint Committee on Cancer (AJCC) TNM classification system is the lung cancer staging system utilized in NSCLC. The stage of cancer is dependent on a combination of these three factors listed below.
Tumor (T) refers to the size/shape and extent of the primary tumor's growth, as well as its specific location. This category can be assigned a letter or number, which correlates directly to the primary tumor's size/size and location.
Nodes (N) refers to the involvement of lymph nodes. This category helps to determine whether the cancer has advanced to the lymphatic system.
Metastasis (M) refers to the spread of cancer to any other organ(s).
The 4 Stages of Lung Cancer (Non-Small Cell)
The four stages of NSCLC are typically represented by Roman numerals (I through IV), indicating stages 0 through 4. As a rule of thumb, with each increase in lung cancer stage, so does the extent of the spread and advancement of cancer.
Occult Stage of Lung Cancer:
In this 'hidden' stage, cancer cells are identified through sputum culture, but the presence of a tumor cannot be specifically confirmed in the lung via bronchoscopy or other imaging mechanisms. Furthermore, the primary tumor may be so minuscule, it is rendered undetectable. There is no lymph node involvement or metastasis in this preliminary stage.
Stage 0 of Lung Cancer:
This is an early stage of lung cancer where the tumor is only localized to the superficial of the lung or bronchi. There is no lymph node involvement or further metastasis to any other organs. Stage 0 may also be referred to as 'carcinoma in situ' by healthcare specialists.
Stage 1 of Lung Cancer:
In stage 1, cancer has officially developed and can be split into two categories, IA and IB. These categories are based on the size/shape of the tumor. There is no lymph node involvement or metastasis to any other organs in this stage.
- Stage IA: The tumor is <3 centimeters (cm) in size/shape.
- Stage IB is classified as having >1 of the following parameters:
- Tumor size/shape >3 cm but <4 cm
- Extension of cancer to the primary bronchus
- Cancer has extended to the deepest membrane layer covering of the lung
- Tumor has led to pneumonitis and/or a collapsed lung due to a partial blockage of the bronchi or bronchioles
Stage 2 of Lung Cancer:
Stage 2 can also be split into two categories, 2A and 2B, which can further be differentiated into subsections based on the size/shape, tumor location, and the extent of lymph node involvement (if any at all). Tumors in stage 2 are generally sizable compared to those found in stage 1 and have started to reach the lymph nodes. Typically, there is no metastasis to other organs.
- Stage IIA (1): The primary tumor is between 4-5 cm and the cancer has extended to lymph nodes on the same side of the chest.
- Stage IIA (2): The primary tumor is 5-7 cm and the cancer has not extended to lymph nodes along with >1 of the following:
- Cancer has extended to the primary bronchus, but not carina
- Cancer has reached the deepest membrane layer that covers the lung
- The tumor has led to pneumonitis and/or a collapsed lung due to a partial blockage of the bronchi or bronchioles
- Stage IB (1): The primary tumor is 5-7 cm with cancer extending to lymph nodes on the same side of the chest in the lung or near the bronchus along with >1 of the following:
- Cancer has extended to the primary bronchus, but not carina
- Cancer has extended to the deepest membrane layer that covers the lung
- The tumor has led to pneumonitis and/or a collapsed lung due to a partial blockage of the bronchi or bronchioles
- Stage IIB (2): There is no cancer extending to lymph nodes, and >1 of the following may be identified:
- Tumor size is >7cm
- One or more small-scale tumors are found in the same lobe as the primary tumor
- Cancer has reached the chest wall, which may involve the chest wall membrane itself, nerve that controls the diaphragm, or the outer lying tissue layer of the heart
Stage 3 of Lung Cancer:
This stage is split into three categories, which include 3A, 3B, and 3C respectively. These categories can be further divided into subsections based on the size/shape, primary tumor location, and the extent of lymph node involvement.
- Stage IIIA (1): The primary tumor may be any shape or size with cancer extending to the lymph nodes on the same side of the chest, around the aorta or trachea, along with >1 of the following:
- Cancer has reached the primary bronchus, but not the carina
- Cancer has extended to the deepest membrane layer covering the lung
- The tumor has led to pneumonitis and/or a collapsed lung due to a partial blockage of the bronchi or bronchioles
- Stage IIIA (2): Cancer has extended to lymph nodes on the same side of the chest, in the lung or near the bronchus, along with >1 of the following:
- Tumor may be any size or shape
- One or more small-scale tumors found in the same lobe as the primary tumor
- Cancer has extended further into the chest wall, which may involve the chest wall membrane, nerve that controls the diaphragm, or the outer lying tissue layer of the heart
- Stage IIIA (3): Cancer has reached the lymph nodes in the lung or near the bronchus along with >1 of the following:
- Tumor may be any size or shape
- One or more small-scale tumors found in a different lobe as the primary tumor
- Potential further cancer spread throughout the chest or proximal area
- Stage IIIB (1): The primary tumor may be any size or shape with cancer extending to lymph nodes on the same side of the chest, or lymph node involvement that has extended to the opposing side of the chest, along with >1 of the following:
- Cancer has reached to the primary bronchus, but not carina
- Cancer has extended to the deepest membrane layer covering the lung
- Tumor has led to a collapsed lung and/or pneumonitis due to a partial blockage of the bronchi or bronchioles
- Stage IIIB (2): Cancer has extended to lymph nodes on the same side of the chest, around the aorta or trachea, with >1 of the following:
- One or more small-scale tumors found in either lobe regardless of the location of the primary tumor
- Further cancer spread throughout the chest or proximal area
- Stage IIIC: Cancer has extended to lymph nodes on the same side of the chest, around the collarbone, or lymph node involvement that has crossed to the opposing side of the chest, along with >1 of the following:
- One or more small-scale tumors found in either lobe regardless of the location of the primary tumor
- Further cancer spread throughout the chest or proximal area
Stage 4 of Lung Cancer:
Stage IV is the most advanced (severe) form of NSCLC. This type of lung cancer has metastasized to other location(s) throughout the body. It is split into two categories, IVA and IVB.
- Stage IVA: The tumor may be any size or shape, and cancer has extended through the lymph nodes with >1 of the following:
- Lymph node involvement in the lung where the primary tumor is not located,
- Cancer is found in the lining or fluid of the lungs or heart
- Cancer spread to an organ not proximal to the lung (ex: brain, liver, kidney, or bone)
- Stage IVB: Cancer has further extended to multiple sites in at least one organ not proximal to the lung.
Small Cell Lung Cancer (Small-Cell)
SCLC makes up approximately 13% of lung cancer occurrences. Smoking tobacco is the chief risk factor for this specific kind of lung cancer. SCLC is split into two subcategories, which include small cell carcinoma (also termed 'oat cell cancer'), and combined small cell carcinoma. This type of lung cancer is typically characterized as evolving and metastasizing relatively quickly and aggressively. However, it tends to respond in a positive manner to therapies like chemotherapy and radiation. Procedures that are generally used in SCLC staging include bone marrow aspiration/biopsy, magnetic resonance imaging (MRI), endoscopic ultrasound (EUS), as well as lymph node biopsy or specialized bone scan.
The Two Stages of Lung Cancer (Small Cell)
SCLC staging is much simpler in comparison to NSCLC, as it is only divided into two stages, limited-stage SCLC and extensive stage SCLC. These stages are primarily utilized when deciding upon potential treatment options. The TNM classification system is still utilized for SCLC, but its use is not as pertinent as it is in NSCLC.
Limited Stage:
Cancer has only extended to a singular lung, the tissues between lungs, and nearby lymph nodes. With limited-stage SCLC, aggressive treatments with combination chemotherapy and radiation therapy are typical favorable treatment options.
Extensive Stage:
Cancer has extended outside of the lung and even beyond. Chemotherapy alone is likely the preferred treatment option here.
Final Thoughts
Understanding the staging process of any cancer is not a simple task. With the help of your team of oncology specialists, they will identify which stage of lung cancer you may have. By understanding and knowing your disease progression, you will ultimately be on the right avenue toward the best treatment options available. Regardless of the type and/or stage of lung cancer, being properly educated on disease development will help you stay informed and keep you on the path to better health.
“Let’s remember that in addition to treating the cancer, we are treating the patient, and you need to be ready for this journey ahead, this illness that you didn’t ask for, uh, but it’s yours now,” Dr. Geoffrey Oxnard, a thoracic oncologist at Boston University School of Medicine, told SurvivorNet in a previous interview.
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