There are two main types of lung cancer: Non-small cell lung cancer and small cell lung cancer. Each has a separate staging system that doctors use to classify how advanced the cancer is.

Staging helps doctors predict the likely outlook for a person who has lung cancer. It can also help them develop the best possible treatment plan.

In this article, we look at the different staging systems for the main types of lung cancer, how they affect the outlook, and an overview of symptoms and diagnosis.

Both the main types of lung cancer have different systems of staging.

Non-small cell lung cancer

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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 80–85% of lung cancer cases. The three main subtypes are:

  • Adenocarcinoma. Around 40% of people with lung cancer have adenocarcinoma. It usually develops in the outer parts of the lung and tends to grow slower than the other two subtypes. This means that there is a better chance of a finding and treating a tumor before it has spread.
  • Squamous cell carcinoma. This accounts for about 25–30% of lung cancers. It grows from the cells that line the inside of the airways. Squamous cell carcinoma usually develops at the center of the lung.
  • Large cell carcinoma. This makes up around 10–15% of lung cancers. It can grow in any part of the lung and tends to grow faster than the other subtypes.

Doctors commonly use the following criteria to stage NSCLC:

  • the size and location of the tumor
  • the number of nearby lymph nodes to which the cancer has spread
  • whether the cancer has spread to distant organs, or metastasized

Using these criteria, they calculate which of the following stages best describes NSCLC:

Stage 1: The tumor is in a single lung and has not spread to any lymph nodes or distant organs.

Stage 2: The cancer has grown to be larger than 3 centimeters (cm) across and may have spread to the lymph nodes inside the lung but not to any distant organs.

Stage 3: The cancer has grown to be larger than 7 cm across and may have spread to lymph nodes at the center of the chest but has not spread to any distant organs. Stage 3 has two subtypes:

  • 3a: The cancer has not spread to the opposite side of the chest.
  • 3b: The cancer has spread to lymph nodes in the opposite lung or near the collar bone.

Stage 4: NSCLC has spread to the other lung, to the fluid around the lung or heart, or to distant lymph nodes or organs.

Small cell lung cancer

Small cell lung cancer (SCLC) accounts for about 15% of all lung cancer cases.

The most common staging system for SCLC breaks the disease down into two categories:

  • Limited stage: At this stage, cancer has only developed on one side of the chest and involves a single area of the lung, the lymph nodes, or both.
  • Extensive stage: Cancer has spread to the opposite side of the chest or outside the chest.

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A person's age and overall health may affect their outlook.

The outlook for a person with lung cancer depends on the type and the stage. Other factors, such as age and overall health, can also affect the outlook.

The ACS uses a survival rate to demonstrate the likelihood that a person will live for 5 years following diagnosis.

This rate compares a person with lung cancer's chance of surviving for 5 years with that of an individual who does not have cancer.

Outlook for non-small cell lung cancer

According to the ACS, people with NSCLC who receive diagnosis and treatment before the cancer spreads from its original location have a 5-year survival rate of 60%.

If the cancer spreads to nearby structures or lymph nodes, the 5-year survival rate reduces to 33%. Once the cancer spreads to distant sites, such as the brain, bones, or liver, a person has a 6% chance of surviving for 5 years.

Small cell lung cancer

SCLC tends to grow and spread quickly, which makes it difficult for doctors to treat and generally leads to a poor outlook.

When the cancer remains localized, the 5-year survival rate is 29%. This drops to 15% once cancer spreads to nearby lymph nodes and 3% if the cancer reaches distant organs.

Screening may not benefit every person who is at risk of lung cancer.

However, those at high risk can increase their chances of identifying and treating lung cancer before it progresses to a later, more dangerous stage.

Doctors recommend a low dose CT scan for lung cancer screening.

The ACS identifies people with the following criteria as suitable for lung cancer screenings:

  • being 55–74 years of age
  • currently smoking or having quit during the last 15 years
  • have a smoking history of at least 30 pack years

They should also be aware of the benefits and risks of screening and take an active involvement in the decision to start. People who choose lung cancer screening need access to a high quality screening and treatment center.

Lung cancer symptoms closely resemble those of bronchitis or pneumonia. This is part of the reason why more than 70% of lung cancers are already in advanced stages before doctors find them, according to a 2015 review.

The ACS recommend seeking consultation if the following symptoms become apparent:

  • a persistent cough that regularly brings up blood or dark phlegm
  • a hoarse voice
  • chest pain
  • shortness of breath
  • wheezing
  • frequent respiratory infections
  • tiredness or weakness
  • a reduced appetite
  • weight loss

New symptoms may develop as lung cancer progresses. These include:

  • headaches, dizziness, or seizures, which may indicate that cancer has spread to the nervous system
  • jaundice, due to cancer spreading to the liver
  • lumps beneath the skin if cancer has reached the lymph nodes
  • back pain
  • hip pain
  • general bone pain

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A doctor may order a chest X-ray to help diagnose lung cancer.

If symptoms suggest the presence of lung cancer, a doctor will first conduct a chest X-ray.

If the X-ray detects signs of a tumor or does not identify a reason for chest symptoms, they will request a CT. A CT scan produces a more detailed image and can reveal a tumor's size, shape, and position in the lung.

The next step is to work out whether the abnormality (typically a nodule or mass) seen on CT scan is cancer. If so, the doctor also needs to determine the type of lung cancer.

To achieve this, the doctor will order a lung tissue biopsy using a needle or surgery. Alternatively, a doctor can investigate cell samples from phlegm or the fluid surrounding the lung.

Doctors use different staging systems according to the type of lung cancer a person has. The stages depend on the size of the tumor, whether it has spread, and where it has spread to.

The World Health Organization (WHO) state that lung cancer is the second most common form of cancer, and the leading cause of cancer death. Sometimes, the symptoms resemble other conditions, such as bronchitis or pneumonia, which means doctors do not always diagnose it until it has reached a later stage.

However, screening can help in some cases, and early diagnosis is a way to identify lung cancer at a more treatable stage.

Anyone who experiences symptoms relating to lung cancer should see a doctor as soon as possible.