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Lung cancer staging: Why it is important and how it works

MD Anderson Cancer Center

June 2, 2022

Ronda Wendler


Lung cancer staging: Why it is important and how it works


When you’re diagnosed with lung cancer, one of the most important things you’ll learn is your cancer’s stage. Staging is a way of describing the location of a tumor or cancer cells in your body, the tumor’s size and whether the cancer is in one spot or has spread.

That knowledge is crucial, says medical oncologist Natalie Vokes, M.D.


“To identify the best treatment plan for you, your doctor first needs to know your cancer’s stage,” Vokes says. “Staging is so critical, in fact, that you should never begin treatment without it.”


But lung cancer is complex, and different forms of the disease are staged in different ways. We spoke with Vokes to learn more.


How is a lung cancer’s stage determined?

You’ll undergo various tests and procedures to learn your cancer’s stage. These usually include MRIs, CT scans and/or PET scans, and lymph node biopsies. You may also have a lung function test to see how healthy your lungs are.


Your doctor will combine the results of these procedures to stage your cancer, using the TNM classification system. These letters stand for:

  • T (tumor) – Describes a tumor’s size and where it’s located

  • N (node) – Reveals if the cancer has spread to the lymph nodes

  • M (metastasis) – Tells whether the cancer has spread to other organs in the body

Why are lung cancers staged?

Besides helping doctors arrive at your recommended treatment plan, lung cancer staging provides an educated estimate for your prognosis. Although each patient is different, cancers with the same stage tend to have comparable results.


Cancer staging is also used to identify clinical trials that patients may be eligible to join. Clinical trials test new, experimental cancer drugs and treatments for specific stages of cancer. If you’re diagnosed with stage IV lung cancer, for example, you may be eligible for a clinical trial of a drug designed to treat stage IV lung cancer.


What are the primary types of lung cancer?

There are two main kinds of lung cancer: non-small cell lung cancer and small cell lung cancer. They’re named based on the way their cells appear when viewed under a microscope. Non-small cell lung cancer cells appear large and round, whereas small cell lung cancer cells are smaller and oval shaped.


Non-small cell lung cancer is the most common type. It accounts for 85% of cases. This type of cancer develops in the cells that line the lung’s surface. It typically grows at a slower rate than small-cell lung cancer and causes few or no symptoms until it has advanced.


Small cell lung cancer accounts for the remaining 15% of all lung cancers. It typically develops in the bronchi, the two large tubes that carry air from the windpipe to the lungs. It’s usually diagnosed in people with a history of smoking. This type of cancer tends to grow and spread faster than non-small cell lung cancer.


Because non-small cell and small cell lung cancers develop from different types of cells and behave differently, they are staged differently.


What are the stages for non-small cell lung cancer?

The general stages for non-small cell lung cancer range from the occult (earliest) stage to stage IV, the most advanced stage:

  • occult stage: Cancer cells are found in the mucus you cough up. This stage is also called hidden cancer, because no tumor is seen on imaging scans or a biopsy.

  • stage 0: Cancer cells are found only in the top lining of the lung or bronchus. They haven’t spread deeper into your lung tissues. This stage is also called carcinoma in situ, Latin for “in its place.”

  • stage I: A small amount of cancer is in your lung tissues but has not spread to your lymph nodes or other parts of your body.

  • stage II: The amount of cancer in your lungs has increased, but it still has not spread to your lymph nodes or distant organs.

  • stage III: Cancer has spread to your lymph nodes in the middle of your chest.

  • stage IV: Cancer has spread widely around your body. It may have spread to your brain, bones or liver.

Each of these stages are further divided into substages based on tumor size and location.


Small cell lung cancer stages

The staging system for small cell lung cancer is simpler. Doctors classify the cancer into two main categories: limited or extensive.

  • Limited stage: Cancer is only in one lung and may have spread to nearby lymph nodes. It can be treated with radiation therapy.

  • Extensive stage: The tumor has spread beyond the originally affected lung, either to the opposite lung or to other organs, like the brain. It is typically too widespread to be safely treated with radiation therapy.

Can a person have both types of lung cancer?

Around 5% to 10% of lung cancers are mixed. This means a person has non-small cell and small cell cancers.


Do lung cancer stages change?

Your lung cancer stage typically stays the same as when you’re first diagnosed, no matter what happens with the disease. For example, if you’re diagnosed with stage II lung cancer, that’s what it will be called, whether it spreads or is successfully treated.


Occasionally, cancer may be restaged with a new round of tests if it goes away, then comes back. Also, patients who seek a second opinion from MD Anderson after being diagnosed elsewhere may be restaged based on their MD Anderson test results.


Lung cancer is a complex disease

Though lung cancer may at first sound like a simple diagnosis, it’s actually a very complex disease. Knowing the stage of your cancer and the details of your treatment can help reduce your anxiety. Whatever your diagnosis, remember that staging isn’t a crystal ball. Many people who are diagnosed with later stage cancer do well with the right treatment.

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