Understanding how lung cancer is staged gives practitioners and patients valuable information about their disease. Staging allows medical professionals to describe cancer based on its location, size, and whether it has spread. First, the lung cancer type must be determined. Then, cancer can be staged to understand the cancer’s individual characteristics better. This information is useful when determining what treatment types are most appropriate. It can also be used to predict how cancer may progress and respond to various therapies.
Determining Your Lung Cancer Type
The first step of lung cancer staging is determining the type of cancer. There are two main categories: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). This is characterized by looking at the cancerous cells using a microscope. NSCLC is the more common type, accounting for roughly 85% of lung cancer cases. A very small percentage of lung cancers are composed of other categories, but these are rare and make up a minority of lung cancer diagnoses.
Non-Small Cell Lung Cancer (NSCLC)Read More
Small Cell Lung Cancer (SCLC)
SCLC is divided into two subtypes based on how the cancerous cells look under a microscope. The two subgroups include small cell carcinoma and combined cell carcinoma (a combination of large and small cell types). This cancer type is usually found in patients who are or have been smokers or were exposed to secondhand smoke regularly. SCLC is also typically more aggressive than NSCLC and is more likely to be diagnosed at an advanced stage.
Lung Carcinoid Tumor
Lung carcinoid tumors are very rare tumors that arise from a different cell type, called neuroendocrine cells. They are slow-growing tumors that can typically be removed with surgery alone. If the tumor is atypical (not typical) in nature, surgery may be followed with chemotherapy or radiation to decrease the risk of recurrence.
This classification system describes three different characteristics of a tumor. This information is then used to help determine the cancer’s stage. This system is also useful for practitioners to concisely give an accurate description of the cancer and easily share this information with other healthcare team members. The TNM classification helps guide treatment decisions and gives practitioners an idea of what to expect regarding how the cancer may respond to certain therapies.
- Tumor (T) refers to the location and physical size of the primary tumor. Numbers 1-4 further describe the cancer, with 4 being the largest tumor size. For example, T1 would represent the smallest primary tumor, and T4 tumors are the largest..
- Nodes (N) describe what lymph nodes are involved, if any. N1-3 characterizes the nearby lymph nodes affected, with 3 being the highest lymph node involvement. N0 would be used if there were no lymph nodes affected.
- Metastasis (M) examines whether or not the cancer has spread/extended to other body parts. M1 means the cancer has spread, and M0 means the cancer has not yet spread.
NSCLC: The 4 Stages of Lung Cancer
NSCLC, the most common type of lung cancer, is further divided into stages to give an accurate and detailed description of the tumor. If the cancer is caught while it is only in the top/outer lining of the lung, it is referred to as stage 0. You may also hear this called ‘in situ’ disease. At this stage, it has not yet grown into healthy lung tissue but is ready to do so. Once the cancerous cells begin to grow, there are four stages of NSCLC. The stage can help select cancer treatment types, but treatment plans are often a combination of surgery, chemotherapy, radiation, immunotherapy, and targeted medications.
In this stage, the cancer has not spread or extended to any other parts of the body, including the lymph nodes. It will sometimes be referred to as 1A or 1B, depending on the physical size of the tumor.
Cancer Treatment Types
Stage 1 NSCLC can be treated with surgery alone. This is often done through either a lobectomy, in which an entire lobe of the lung is removed or wedge resection, in which only a portion of the lobe is removed. Typically, most surgeons prefer a lobectomy to ensure all the cancer has been eliminated, but that may not be possible depending on the size or location of the tumor or the patient’s physical health status.
After the cancer is removed, the outer edges of the tumor are inspected for cancerous cells. If found, this is referred to as a positive margin. In this instance, the surgeon may have to go in again and remove a larger portion. The tumor can also be tested at this time to help determine if the patient should receive chemotherapy or radiation following surgery, which will help decrease the chance of recurrence. The recurrence rate for stage 1 is about 1 in 3 people, meaning additional treatment may be warranted to help prevent this.
Another Stage 1 lung cancer option is Stereotactic Body Radiation Therapy (SBRT). This technique uses highly focused radiation to treat the tumor. Typically, patients treated with SBRT will need between 3-5 treatments with radiation to treat the tumor. Currently, SBRT is reserved for patients who can’t have surgery due to medical issues, but current studies are looking to see if SBRT may be an option for all patients.
In stage 2, the cancer has spread, but only to lymph nodes that are close (scientifically termed ‘proximal’) to the primary tumor. It is also broken down further into 2A and 2B depending on the primary tumor size, location, and the extent to which it has extended to the lymph nodes. Typically, stage 1 tumors are ≤ 5 cm and classed as stage 2 if their tumor size is >5 cm but ≤7 cm. Although the size of stage 2 tumors may seem large, they still have not spread beyond the regional lymph nodes.
Cancer Treatment Types
Stage 2 is often treated similarly to stage 1, with the mainstay of therapy being to remove the tumor through surgery, if possible. A wedge section or lobectomy is typically performed, although in some circumstances, the removal of an entire lung, pneumonectomy, is required.
Following surgery, the tumor is again tested for positive margins, indicating that additional surgery may be needed. This testing can also help determine if a post-surgery treatment is required. This is typically either chemotherapy or focused radiation, but other therapies may be used in combination with traditional treatments, depending on the distinct characteristics of the tumor itself.
In stage 3 lung cancer, the cancer has spread to lymph nodes outside the lung; however, it has not yet extended to distant (scientifically termed ‘distal’) organs. The area between the lungs, called the mediastinum, is a common location for the cancer to spread. This stage is further divided into 3A, 3B, and 3C based on the size and extent of the disease, with C having the most significant disease progression.
Cancer Treatment Types
For this stage, a combination of chemotherapy, radiation therapy, and immunotherapy forms the backbone of treatment. Sometimes these treatments may be used before surgery (called neoadjuvant therapy) to decrease the tumor’s size and spread to lymph nodes to make surgery more manageable. However, the tumor is often located in a position that does not make surgical removal possible, even after chemotherapy and/or radiation.
The tumor is typically tested for the expression of certain proteins, which could also make immunotherapy or targeted medications an option at this stage. Immunotherapy is FDA-approved for stages 3 & 4.
Stage 4 indicates advanced disease that has spread or metastasized to distant organs. Unfortunately, the brain is the most common site of metastasis. The bone and liver are other common sites of metastasis. Stage 4A describes when the lung cancer has only spread to one other site, whereas stage 4B has progressed to multiple sites of metastasis.
Cancer Treatment Types
Treatment of stage 4 varies greatly based on the extent and location of metastasis. You need to treat both the primary tumor as well as any metastases, which is why treatment at this stage is quite complex. Surgery is often no longer an option in most cases. This is simply because the cancer has typically spread beyond what is operable. The patient is treated with some combination of chemotherapy, radiation, immunotherapy, and targeted therapies. The exact combination of these medications will vary from patient to patient and depends on genetic testing or protein expression in the cancerous cells. The sites of metastasis will also affect treatment choice. Although surgery is not typically an option for the primary lung tumor itself, it may still be an option for a site of metastasis, such as the brain.
In advanced disease, the treatment focus may shift more to palliative care. Although palliative care can and should be started at any time and used in conjunction with standard treatment, it is more commonly the priority in late stage disease progression. The goal of treatment with palliative care is to alleviate or manage the side effects and minimize the mental, emotional, and functional stress the cancer puts on the patient. This helps patients to live more comfortably and enjoy what is left of life.
SCLC: Staging Considerations
SCLC is typically subdivided into two groups: limited and extensive stages. It is rarely diagnosed in the limited stage. Usually, by the time SCLC is detected, the cancer has already spread to other sites:
- Limited stage SCLC may have spread to the lymph nodes in the same lung or perhaps in the mediastinum.
- Extensive stage SCLC has spread, or metastasized, to other distinct sites.
Cancer Treatment Types
Radiation and chemotherapy are often used as the first step in treating SCLC. Surgery is rarely possible to treat SCLC due to the progressive nature of the cancer type, but it can be used in some circumstances. The patient’s overall health and lung condition also play a role in determining if a patient is able to receive certain treatments. Chemotherapy may be combined with either radiation or immunotherapy to treat SCLC.
How is Lung Cancer Staged?
A chest x-ray is often the first scan that indicates lung cancer. It would typically be followed up with either aCT scan. Depending on the tumor size, some patients will also have a PET scan and an MRI of the brain. These types of scans give a better idea of the location and extent of the cancer as well as if there has been any spread of the cancerous cells or metastasis. This helps to determine which of the 4 stages of lung cancer the patient is in and what is an appropriate treatment.
Lung cancer can also be biopsied to give more information regarding the characteristics of the tumor. This biopsy can be used to perform genetic testing for the expression of certain proteins that help to guide treatment decisions.
How Lung Cancer Stage Affects Prognosis
The lung cancer stage at diagnosis plays an important role in estimating overall survival. NSCLC has a better prognosis than SCLC. Lung cancer prognosis is described based on a 5-year survival rate. This represents the percentage of patients that are still alive five years from diagnosis. Between 2011-2017, the 5-year survival rate for all stages of NSCLC was 26% compared to 7% for SCLC. The stage at diagnosis is correlated to overall survival. For NSCLC that was still localized upon diagnosis, compared to NSCLC that had distant metastasis, the 5-year survival was 64% and 8%, respectively. Local versus distant SCLC showed 29% and 3% survival rates, respectively. This is why screening patients at high risk for lung cancer is so critical. Early detection and treatment make a big difference in the prognosis of the disease and have been shown to improve survival in prospective randomized trials.
It is important to remember that these statistics do not account for various gene mutations or specific cancer subtypes that likely impact prognosis. The current staging system does not include certain genetic types and protein expressions in the cancerous cells. This information will significantly impact how the cancer responds to certain treatments. The treatments used in lung cancer are constantly evolving and the 5-year survival from the last several years is most likely improving as newer treatments, such as targeted medications and immunotherapy, are being utilized more commonly and earlier in disease progression.