Let's Talk About Lung Cancer Stages
If you’ve been diagnosed with this disease, the path your treatment will take depends on your cancer stage. Learn more about what each stage means, and how doctors determine where your cancer falls.
There’s an overwhelming amount of info that comes at you right after hearing the words, “You have lung cancer.” It’s hard to digest it all, that’s for sure. But there is one thing that’s super-important to tune into—and that’s learning your lung cancer stage. This information dictates treatment options and helps direct decision-making. When you’ve just been diagnosed, though, it’s hard to know a stage I from a stage IV. Start by consulting our easy-to-digest guide to lung cancer staging, right here.
Our Pro Panel
We went to some of the nation’s top experts in lung cancer to bring you the most up-to-date information possible.
Jacob Sands, M.D.
Thoracic Medical Oncologist and Instructor in Medicine
Dana-Farber Cancer Institute and Harvard Medical School
Elisabeth Dexter, M.D.
Thoracic Surgeon and Quality Assurance Officer for the Department of Thoracic Surgery
Roswell Park Comprehensive Cancer Center
Josephine (Joy) Feliciano, M.D.
Medical Oncologist, Assistant Professor of Oncology
The Johns Hopkins University School of Medicine
Cancer cells can break away from your initial tumor and travel to your lymph nodes. Once there, cancer cells multiply, forming new tumors. Additionally, cancer cells can leave your initial tumor and travel through your blood to form new tumors.
Not entirely. Although survival rates are generally grouped based on stage (a.k.a how far your cancer has spread), other factors affect your prognosis such as age, overall health, how well your cancer responds to treatment, and more.
About 80% of people of individuals are diagnosed at stage III or IV lung cancer, which can mean that the disease has already metastasized to other organs beyond the lungs.
Stage 0 lung cancer is also called lung carcinoma in situ, or pre-cancer. At this stage, lung cancer is present only in the top layer of cells of the bronchi, bronchioles or alveoli without reaching into the layers below.
To Recap, What Is Lung Cancer?
Lung cancer refers to a mutation in the DNA of a single cell or cells in your lungs that causes cells to begin growing abnormally. When these cells replicate, that DNA glitch does as well. After enough of these abnormal cells develop, they may cluster together, forming a mass or tumor in your lungs. And boom: Lung cancer.
Lung cancer poses a particular challenge because as the tumor grows, it cuts off the supply of oxygen to the remaining healthy lung tissue, eventually destroying it. This makes it difficult to breathe and also challenging to circulate oxygen from the lungs throughout the body.
While most cases of lung cancer are caused by smoking cigarettes, people who have never smoked can also develop this cancer. Lung cancer is the second-most common cancer type in the U.S., with more than 228,000 people diagnosed each year. If you develop lung cancer, you typically have one of two types: the slower-growing non-small cell lung cancer (NSCLC) or faster-spreading small cell lung cancer (SCLC).
How Is Lung Cancer Type Determined?
In order to zero in on which type of lung cancer (small cell or non-small cell) you have, your care team will review your symptoms, blood tests, and imaging tests. Imaging tests determine whether your lung cancer has spread. Various combos of tests can be done and often include:
Computed tomography (CT) scan: A combination of x-rays taken from different angles allows a computer to generate a three-dimensional image of organs and tissues inside your body.
Positron emission tomography (PET) or integrated PET–CT scan: After you receive a small dose of a radioactive drug, known as a tracer, the scan machine follows as it travels through your body. Tissues with higher metabolic rates, such as tumors, absorb more of the tracer, which then appears on the scan.
Bone scan (generally if a PET–CT isn’t available)
MRI of your chest and/or brain
These tests, along with possibly a minimally invasive biopsy procedure, lets your physician decipher the type of lung cancer you have. From there, your doctor will determine the extent of the disease (your stage) and best course for treatment. Even if symptoms improve during treatment, the stage of your lung cancer always remains the same.
How Is Non-Small Cell Lung Cancer Staged?
There are a few different ways non-small cell lung cancer (NSCLC) is staged. The first, from the National Cancer Institute, is based on the SEER (Surveillance, Epidemiology, and End Results) database. This method defines lung cancer stage based on how far it has spread.
Localized: Your lung cancer has not spread outside of your lung.
Regional: Your cancer has spread outside your lung to nearby tissue or lymph nodes inside your chest.
Distant: Your cancer has spread to other organs in your body, such as your brain or your other lung.
The second common staging system comes from the American Joint Committee on Cancer and the International Association for the Study of Lung Cancer. Known as the TNM (Tumor, Nodes and Metastasis) classification system, in this method, your lung cancer is assigned a letter or number to describe the following:
T: This refers to the size and location of original tumor.
N: This references nearby lymph nodes involvement.
M: This stands for metastasis status or which, if any, organs your cancer has spread to.
Next, your care team attaches a number after T, N and M to provide more details about each factor. Higher numbers mean the cancer is more advanced.
For instance, a T number or “score” is derived from the original tumor’s size, plus the location and size of any additional tumors. Scores range from TX (no tumor can be measured) to T4 (tumor is more than 7 centimeters in diameter or a tumor of any size that invades the trachea, esophagus, or other specific organ). Making matters even more complicated, T scores can also include a secondary letter which notes things like the size of specific tumor features.
Meanwhile, N scores can range from NX (no nodes can be evaluated) to N3 (the higher the number, the more nodes that contain cancer). And M scores include MX (metastasis cannot be measured), M0 (cancer hasn’t spread), and M1 (cancer has spread).
There is still one more method of lung cancer staging and it’s likely the one you’re most familiar with.
What Does Stage l to Stage IV Non-Small Cell Lung Cancer Mean?
The TNM system is an effective and super-detailed way for your care team to understand your lung cancer stage, but it’s also pretty complicated for the average patient to digest. In the end, TNM is really more useful to your care team than you. Because of that, your T, N, and M scores will be tallied and synthesized to a more concise, simplified, overall stage. These stages utilize the Roman numerals from I to IV, with stage IV (4) being the most advanced stage of lung cancer.
And because nothing is as simple as you want it to be, stages can still be subdivided with letters, as well. (More on that later.) Here’s a simplified version of how it shakes out:
Stage I: Cancer is only in one lung.
Stage II: Cancer is in one lung and nearby lymph nodes.
Stage III: Cancer is in one lung and in the nodes located in your chest or above your collarbone.
Stage IV: Cancer has spread to both lungs, the fluid around the lungs, or another organ in your body.
The above is an abridged version. Let’s take a closer look at how lung cancer gets placed into these different categories.
Stage I Non-Small Cell Lung Cancer
In addition to the tumor being small and only present in one lung, stage I lung cancer means that your cancer has not spread to any lymph nodes and has not metastasized. Approximately 25% of NSCLC are diagnosed at Stage I. There are two subcategories of Stage I lung cancer:
Stage IA: Your tumor is no more than 3 centimeters in greatest dimension.
Stage IB: Your tumor is between 3-4 centimeters in greatest dimension, grown into your main bronchus (the airway into the lungs) or pleura (lung lining) or it may have also caused a partial or full lung collapse or led to pneumonitis (lung tissue inflammation).
Stage II Non-Small Cell Lung Cancer
Still a small tumor and only in one lung, stage II lung cancer has not spread to other organs but may have reached the lymph nodes. About 8% of NSCLC patients are diagnosed at this stage. There are two subcategories of stage II lung cancer.
Stage IIA: Your tumor is larger than 4 centimeters in greatest dimension, but no more than 5. There is no lymph node involvement. In addition, your lung cancer may have also spread to your main bronchus and/or the pleura. You may also experience a partial or full lung collapse or pneumonitis.
Stage IIB: There are two definitions for IIB. Either the cancer has not spread to any lymph nodes and hits one or more of the following notes:
Your tumor is 5-7 centimeters in greatest dimension.
One or more tumors are located in the same lobe.
Your cancer has spread to either your pleura, chest wall, the phrenic nerve that controls the diaphragm, and/or the pericardium sac around the heart.
Stage IIB: The tumor is no more than 5 centimeters in greatest dimension and has spread to nearby lymph nodes on the same side of the chest as the tumor. In addition, your lung cancer has spread to either the main bronchus or the pleura and/or you experience a partial or full lung collapse and/or develop pneumonitis.
Stage III Non-Small Cell Lung Cancer
All stage III lung cancers have spread to lymph nodes within the middle of the chest, but still have not metastasized to distant parts of the body. Some refer to stage III lung cancer as “locally advanced.” About 27% of people with lung cancer are diagnosed at this stage.
Stage III has three subtypes and multiple criterium for each (it’s complicated, we know):
Stage IIIA: Your tumor measures 5 centimeters in greatest dimension or smaller and the only lymph node involvement is on the same side of the chest as the original tumor. At the same time, your lung cancer may or may not have spread to the main bronchus and/or your pleura, and you may or may not experience a whole or partial lung collapse or develop pneumonitis.
Stage IIIA: The only lymph node involvement is on the same side of the chest as the primary tumor. Also, one or more of the following is true:
Your tumor is larger than 5 centimeters in greatest dimension, but less than 7.
One or more tumors are located in the same lobe.
Your cancer has spread to your pleura, the chest wall, the phrenic nerve, or the pericardium sac.
Stage IIIA: The only lymph node involvement is on the same side of the chest as the primary tumor. In addition, one or more of these is true:
Your tumor measures larger than 7 centimeters in greatest dimension.
One or more tumors are located in a different lobe than the primary tumor
Your tumor is any size and has spread to either the trachea, carina (ridge of cartilage in the trachea), esophagus, breastbone or backbone, diaphragm, heart, aorta, vena cava or the nerve that controls your larynx.
Stage IIIB: To be considered stage IIIB lung cancer either your tumor measures 5 centimeters in greatest dimension or smaller, appears in lymph nodes on the opposite side of the chest as your main tumor or above your collarbone on the same side as your primary tumor, and one or more of the following is true:
Your lung cancer may have spread to the main bronchus and/or the pleura.
You may have experienced a full or partial lung collapse or developed pneumonitis.
Stage IIIB: Your lung cancer tumor can be any size and it’s spread to nodes on the same side of the chest as your main tumor. Also, one or more of the following is found:
One or more tumors can be found in the same or a different lobe than the primary tumor.
Your lung cancer has spread to your pleura, chest wall, phrenic nerve, pericardium sac, trachea, carina, esophagus, breastbone, backbone, diaphragm, heart, aorta, vena cava or the nerve that controls the larynx.
Stage IIIC: The lung cancer tumor may be any size and has spread to either the lymph nodes above your collarbone on the same side of your chest as your primary tumor or it spread to the nodes on the opposite side of your chest. In addition, either or both may be true:
One or more tumors can be found in the same or a different lobe as your primary tumor.
Your lung cancer has spread to your pleura, chest wall, phrenic nerve, pericardium sac, trachea, carina, esophagus, breastbone or backbone, diaphragm, heart, aorta, vena cava or the nerve that controls the larynx.
Stage IV Non-Small Cell Lung Cancer
At this stage, your lung cancer tumors can be any size. They’ve now metastasized (spread) to distant parts of the body. Lymph nodes may or may not be involved. This stage is often referred to as “advanced disease” and about 39 percent of NSCLC patients are diagnosed at this stage. There are two subtypes:
Stage IVA: Here, your lung cancer has spread either from one lung into the other lung, the pleura, the pericardium sac; and/or tumors have spread to one site outside the chest.
Stage IVB: Your lung cancer has spread to multiple sites outside the chest area, such as your bones and adrenal gland.
What About Carcinoma in Situ and Occult Lung Cancer?
There are two other stages of NSCLC that are not included in the Roman numeral roundup. First, there’s Stage 0, which is carcinoma in situ (CIS). This is considered a pre-cancer because it’s found only in the top layer of cells that line your air passages, without reaching into the layers below (when it officially becomes lung cancer). About 50 percent of CIS lesions eventually turn into cancer.
The second type is occult (or hidden) lung cancer. Here, the main tumor either cannot be assessed or cancer cells are detected in a sample of your sputum (a mix of saliva and mucus), but the cancer itself cannot be found with other testing. The 5-year survival rate for occult lung cancer is up to 85%. About 12% of people with NSCLC are diagnosed at an unknown or occult stage.
What Are the Stages of Small Cell Lung Cancer?
While both SEER and the TNM staging system are used for NSCLC, they are generally not used for small cell lung cancer. The reason: The vast majority of SCLC are already metastasized when diagnosed. Because of this, most physicians will use a pared down staging system that divides SCLC into just two stages: limited stage and extensive stage.
Limited-Stage Small Cell Lung Cancer
Here, the disease is confined to the side of your chest where your cancer started, but still could metastasize to same-side lymph nodes or other parts of the same-side lung. One in three people with SCLC is diagnosed with limited stage.
Extensive-Stage Small Cell Lung Cancer
In extensive-stage, the disease has spread throughout the lung where cancer originated. It can be found in the other lung, lymph nodes on the other side of your chest, or other areas of the body including your bone marrow. (If your cancer has spread to the fluid around your lungs, some physicians will place your lung cancer in this stage, too.) About 67% of SCLC are diagnosed at this stage.
Without a doubt, the different staging systems and complex breakdowns within each system is confusing. But there is a reason for the seemingly endless permutations of stages, letters, and numbers. The better your doctor is able to zoom in on exactly where your cancer is, how big, and how far it has spread, the more accurate your treatment will be, raising the odds of a healthy recovery.
Lung Cancer Stages: Journal of Thoracic Oncology. (2010). “Trends in Stage Distribution for Patients with Non-Small Cell Lung Cancer: A National Cancer Database Survey.” jto.org/article/S1556-0864(15)32963-4/fulltext
Carcinoma in Situ: Journal of Thoracic Disease. (2019). “Predicting Progression of in situ Carcinoma in the Era of Precision Genomics.” ncbi.nlm.nih.gov/pmc/articles/PMC6626772/
Occult Lung Cancer: National Cancer Institute. (2010). “Five Year Survival Rates.” training.seer.cancer.gov/lung/intro/survival.html
SCLC Stages: American Cancer Society. (n.d.). “Small Cell Lung Cancer Stages.” cancer.org/cancer/lung-cancer/detection-diagnosis-staging/staging-sclc.html