The Stages of Lung Cancer, Explained
A patient's prognosis depends a lot on how big their tumor is and how far it's spread.
Lung cancer is a serious disease with sobering statistics: It’s the leading cancer killer of both men and women in the US, according to the American Lung Association, and more than half of lung cancer patients die within one year of being diagnosed.
But those numbers don’t tell the whole story. When it comes to prognosis and life expectancy after a lung cancer diagnosis, the stage of the disease makes a big difference. Patients diagnosed when a tumor is still very small, for example, have a much better chance of beating their cancer and living for many years after a diagnosis.
“Receiving a cancer diagnosis is a life-changing event, and it’s always a difficult conversation to have with patients,” says Rafael Santana-Davila, MD, a medical oncologist at Seattle Cancer Care Alliance and associate professor at the University of Washington School of Medicine. “That being said, the conversation can really vary depending on the stage of the disease.”
Here is what patients and their loved ones should know about the stages of lung cancer, as defined by the American Cancer Society and the American Joint Committee on Cancer (AJCC), and how each stage is diagnosed and treated.
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Non-Small Cell Lung Cancer: Stages 0 to 4
About 85% of lung cancers are classified as a type called non-small cell—a name that dates back to the early days of lung cancer research, when scientists noted that some types of lung cancer cells were bigger than others.
Once non-small cell lung cancer is diagnosed, doctors then have to determine what stage the disease is in—or, in other words, how large the tumor has grown and how far it has spread. Based on the tumor’s size and location, it is defined as one of the following.
Stage 0: This stage is also called carcinoma in situ, which means cancer “in place.” This is used to describe a tumor that is only found in the very top layer of cells lining the lung’s air passages; it hasn’t yet invaded any deeper tissue, and it hasn’t yet spread anywhere else in the body. Because of this, it can usually be removed easily via a minimally invasive surgery.
Stage 0 can also be used to describe a “hidden” cancer, in which cancer cells are found in coughed-up mucus or other lung fluids, but a tumor can’t actually be found in the lung tissue itself. Because doctors can’t find the actual location of the tumor, it’s assumed that it has not yet spread or grown very large.
Stage 1: A diagnosis of Stage 1 lung cancer means that a tumor is discovered, but it is still localized within the lungs. “It hasn’t yet spread to any lymph nodes or to other areas, and the cancer is small enough that it can be taken out surgically,” says Dr. Santana-Davila.
This stage is further divided into 1A and 1B, depending on how large it is and where it is found. Stage 1A is generally used to describe a tumor that is less than 3 centimeters and does not affect the main branches of the bronchi, the central structures of the lungs.
Stage 1B is used to describe larger tumors (between 3 and 4 centimeters); those that have started to grow into main sections of the lungs; or those that are partially blocking the airways but still have not spread to lymph nodes or other parts of the body.
Stage 2: Tumors that are slightly larger or in more dangerous parts of the lungs are considered Stage 2. This stage is also divided up into substages: Stage 2A describes a tumor that is between 4 and 5 centimeters across, while Stage 2B may describe a smaller tumor that has spread to nearby lymph nodes.
Stage 2B can also be used to describe a tumor that has grown into parts of the cardiovascular system that are harder to operate on—like the chest wall, phrenic nerve (which passes from neck to the diaphragm), or membranes surrounding the heart. It can also describe a situation in which two or more tumors are found in the same lobe of a lung.
Stage 3: A diagnosis of Stage 3 lung cancer means that the tumor has spread to nearby lymph nodes. “The cancer is now in the center part of the chest,” says Dr. Santana-Davila, “or it’s big enough that it’s touching some very important structures in which surgery cannot be easily done.” Instead, chemotherapy and radiation are usually used to shrink the tumor or tumors.
Stage 3 is divided into Stage 3A and 3B depending on the tumor’s size and the location of the affected lymph nodes. For example, a tumor that has spread to lymph nodes around the mediastinum—the space between the lungs—is classified as Stage 3A, while a tumor that has spread to lymph nodes near the collarbone is classified as Stage 3B.
There is also a Stage 3C, which describes a larger or more invasive tumor that has spread to distant lymph nodes or has grown into the heart, windpipe, esophagus, spine, or diaphragm.
Stage 4: Stage 4 lung cancer is also called metastatic lung cancer because it has spread to other organs and is no longer considered curable.
Stage 4A means the tumor has either spread to both lungs; cancer cells have been found in fluid around the lung or heart; or the tumor has spread outside the chest to either a distant lymph node or another organ—commonly the liver, bones, or brain, says Dr. Santana-Davila.
Stage 4B also means the cancer has spread outside the chest but has also been detected as more than one tumor. In other words, it has appeared in multiple places throughout the body.
Unfortunately, most lung cancer patients are not diagnosed until Stage 4. “This is a very aggressive disease, so it can progress very rapidly from Stage 1 all the way to metastasis,” says Dr. Santana-Davila.
In addition, the lungs are very adaptable—and they’re good at hiding tumors. “You can have a big mass growing within the lungs, and the rest of the lungs will take over and you’ll never know it’s there,” says Dr. Santana-Davila. “In contrast, when a woman has a pea-sized mass growing in her breast, she might feel it right away.”
Small-cell lung cancer: Limited- and extensive-stage disease
The other major type of lung cancer, known as small-cell lung cancer, does not follow the same staging classification. Instead, it’s divided into limited-stage and extensive-stage disease.
Limited-stage disease is used to describe lung cancer that’s only found within one lung, and may be found in the mediastinum between the lungs. Limited-stage disease generally correlates with Stage 1, 2, or 3 of the traditional cancer staging classification.
Extensive-stage disease correlates with Stage 4, or metastatic cancer. This means that the cancer has spread to the other side of the chest or to distant organs and can only be managed with chemotherapy or radiation—not cured or removed via surgery.
At this point in the disease, curing the cancer is not an option. But it can be managed so that symptoms are lessened and life expectancy is extended, he adds. “People are living longer than ever before with metastatic lung cancer,” says Dr. Santana-Davila. “It may not be curable, but it certainly is treatable—and it’s no longer an immediate death sentence the way it used to be.”