What are the stages of lung cancer?
Staging helps doctors predict outlook and develop the best possible treatment plan.
Both the main types of lung cancer have their own systems of staging.
Non-small cell lung cancer
Most cases of lung cancer are non-small cell lung cancer.
According to the American Cancer Society (ACS), non-small cell lung cancer (NSCLC) accounts for about 80 percent of lung cancer cases. The three main subtypes of NSCLC are:
- Adenocarcinoma. This accounts for 40 percent of lung cancer cases. It is usually found in the outer parts of the lung. It tends to grows slower than the other two subtypes, so there is a better chance of a tumor being found before it has spread.
- Squamous cell carcinoma. This accounts for about 25-30 percent of lung cancers. It grows from the cells that line the insides of the lung's airways. Squamous cell carcinoma is usually found at the center of the lung.
- Large cell carcinoma. This accounts for 10-15 percent of lung cancers. It can be found in any part of the lung, and tends to grow faster than the other subtypes.
NSCLC is most commonly staged using a system called TNM classification:
- T - tumor size and location
- N - the number of nearby lymph nodes that have become involved
- M - metastasis, or how far the cancer has spread
Using a combination of T, N, and M scores, doctors can categorize NSCLC into four different stages:
- Stage 1 is when the tumor is in a single lung, and has not spread to any lymph nodes or distant organs.
- Stage 2 means that cancer has spread to the lymph nodes inside the lung, but has not spread to any distant organs.
- Stage 3 is diagnosed when cancer has spread to lymph nodes at the center of the chest, but has not spread to any distant organs.
- In stage 3a, cancer has not spread to the opposite side of the body.
- In stage 3b, it has spread to lymph nodes in the opposite lung, and has progressed above the collar bone to the throat and neck.
- Stage 4 is diagnosed when cancer has spread throughout the body.
Outlooks for these stages are usually given as the percentage of people still living 5 years after their diagnosis. The following rates are from a 2015 review article in Biochimica et Biophysica Acta:
- stage 1: 60-80 percent
- stage 2: 30-50 percent
- operable stage 3a: 10-15 percent
- inoperable stage 3a: 2-5 percent
- stage 3b: 3-7 percent
- stage 4: 1 percent
Small cell lung cancer
Small cell lung cancer (SCLC) accounts for about 15 percent of all lung cancer cases. The most common staging system for SCLC breaks the disease down into two categories:
- Limited stage, when there is cancer on only one side of the chest.
- Extensive stage, when cancer has spread to the opposite side of the body.
SCLC tends to grow and spread quickly, which makes it difficult to treat. The overall 5-year survival rate is about 5-10 percent, with better outlooks for limited stage than extensive.
Symptoms and screening
A doctor should be consulted if a person is coughing up blood or has a persistent cough.
However, the earlier lung cancer is detected, the better the chances are of it being treated successfully. The ACS say that a doctor should be consulted if anyone:
- has a persistent cough, or is coughing up blood or dark-colored phlegm
- has a hoarse voice, chest pain, shortness of breath, or is wheezing
- frequently has respiratory infections
- feels tired or weak, or has lost their appetite and is losing weight
As lung cancer progresses, new symptoms can arise. Some of these include:
- headaches, dizziness, or seizures, due to cancer spreading to the nervous system
- jaundice, due to cancer spreading to the liver
- lumps beneath the skin, due to cancer spreading to the lymph nodes
- back pain, hip pain, or general bone pain
Even without any of these symptoms, preventive lung cancer screening may be advised. Though no significant benefit has been shown for low-risk patients, there is strong evidence that screening in heavy smokers can significantly reduce mortality.
If symptoms are suspicious, a doctor will first conduct a simple chest X-ray. If signs of a tumor are detected, a CT, MRI, or PET scan will then be ordered. These scans produce a more detailed image and can reveal a tumor's size, shape, and position.
The next step is to work out whether the tumor is cancerous, and if so, what type of lung cancer it carries. To do this, it is necessary to look at lung cells under a microscope and run some genetic tests.
A lung tissue biopsy can be performed using a needle or with surgery. Alternatively, cell samples can be taken from phlegm or the fluid surrounding the lung.
Based on the information collected, a treatment plan can then be developed. Treatment may include a combination of methods, depending on the stage and type of lung cancer, and the genetic makeup of the tumor.
The traditional forms of treatment are surgery, radiation, and chemotherapy:
- Surgery: If cancer is detected early enough, it may be possible to remove the main tumor and other cancerous cells.
- Radiation: Radiation damages the DNA of cancer cells until they can no longer spread, effectively shrinking or killing a tumor.
- Chemotherapy: Drugs that are injected intravenously interfere with the cancer cell DNA, stopping them from growing and spreading.
However, radiation and chemotherapy drugs are unable to differentiate between healthy cells and cancer cells. As a result, healthy cells are also damaged with these treatments.
Aside from these traditional therapies, new drugs that only attack cancer cells are becoming more readily available. They usually have less severe side effects, and can often treat cancers that chemotherapy cannot.
- Targeted therapies: These drugs target specific proteins that only cancer cells produce. These proteins result from abnormal DNA alterations, which can be identified through the genetic testing of tumors.
- Immunotherapy: Certain proteins on the surface of immune cells act as on and off switches, so that healthy body cells can signal them not to attack. Immunotherapy drugs work by keeping these proteins switched on, so that the immune system works to attack cancer cells.
If treatment isn't possible, there are therapy programs that work to ease symptoms, relieve pain, and provide the best possible quality of life. This kind of therapy is called palliative care.
A recent article in the New York Times Magazine profiles Dr. B. J. Miller, former executive director of the Zen Hospice Project, a palliative care program that works to "reincorporate [a patient's] version of reality, of normalcy, to accommodate suffering."
How to reduce the risk of lung cancer
The World Health Organization (WHO) state that lung cancer is the second most common form of cancer, and the leading cause of cancer death.
The single greatest risk factor for lung cancer is tobacco use. A 2012 National Institute of Health study found that nearly 800,000 lung cancer deaths were averted in the United States between 1975 and 2000 due to a decrease in the number of smokers.
Accordingly, the best way to reduce the risk of lung cancer is to not smoke or to quit smoking.