What are the stages of lung cancer?

In the UK, there are around 38,000 new cases of lung cancer every year. It is the third most common type of cancer, according to the World Cancer Research Fund.

Those who smoke are most at risk of developing lung cancer, and these people account for almost 9 in every 10 cases. This said, although the risk is relatively lower, non-smokers can also develop lung cancer. These can be due to several small risk factors, including: passive smoking, working with radioactive materials, chromium, nickel, or asbestos, living near background radiation, and air pollution.

What are the types of lung cancer?

Cancer develops when certain cells in the body start to change, escaping from the body's normally carefully controlled production of new cells. There are three main types of lung cancer:

• Primary lung cancers - arise from cancerous cells in the lung.
• Secondary lung cancers (lung metastases) - arise from cancerous cells which have spread from another part of the body.
• Mesothelioma - arises from the tissue lining of the lung (the pleura). Strictly speaking, this is not a lung cancer.

There are two types of primary lung cancers:

• Non-small-cell lung carcinoma (NSCLC) - the most common type of lung cancer. The three common subtypes of NSCLCs are adenocarcinoma, squamous cell carcinoma and large-cell carcinoma.
• Small-cell lung carcinoma (SCLC) - much less common, accounting for around 3-4 in 10 cases of lung cancer. These cells are smaller in size and grow and spread more quickly, meaning SCLC is often at an advanced stage when diagnosed.

Lung cancer survival rates

According to Cancer Research UK, 10% of people diagnosed with lung cancer live for 10 or more years. Survival rates for lung cancer after ome year are 37.1% for men and 44.5% for women. Beyond five years, this rate drops to 13.8% for men and 19% for women. As well as sex, age is also a factor in lung cancer survival rates, with mortality being lowest for those within the age range of 15-39 years.

Yet research has shown that lung cancer survival rates are also strongly correlated to the stage of the lung cancer at the time of diagnosis. The earlier the stage, the higher the chance a person has of living longer. According to the Office for National Statistics, in England in 2019 88% of patients diagnosed at stage 1 survived their disease for at least one year, compared to 19% of patients diagnosed at stage 4 - the latest stage.

Recently, a new blood test has been developed which can help to diagnose lung cancer at an early stage. This is a positive development that will likely increase survival rates overtime.

What is cancer staging?

As a determinant not just of survival but also optimal treatment for lung cancer, cancer staging is critical. In a nutshell, the stage of the lung cancer is a measure of how much the cancer has grown and spread. This size of growth/spread can be divided into three categories:

• Local growth and damage to nearby tissues.
• Spread to lymph channels and lymph glands (nodes). Tumour cells are carried in the lymph channels to other parts of the body, where they are deposited - so-called metastasis.
• Spread (metastasis) to other areas of the body.

By measuring the stages of lung cancer, healthcare specialists find out how large the tumour is and how far the cancer has spread within the body. By establishing how advanced the lung cancer is, the lung cancer stages inform specialists on the treatment options that can be used and how effective they may be.

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What are the stages of lung cancer?

Lung cancer specialists can use the same staging system for NSCLCs and SCLCs. Your doctor may tell you that you have 1 out of 5 possible stages of lung cancer (stages 0-4). These lung cancer stages are based on:

• Tumour size (cancerous cells).
• Whether the tumour has spread into nearby parts of the lung, or outside of the lung.
• Whether the tumour is in nearby lymph nodes (in the chest or further away).
• Whether the tumour has spread further to other parts of the body.
• Other factors, such as whether the lung has partly or fully collapsed.

To determine these factors, specialists use a staging system called TNM, where:

• T describes the size of the tumour.
• N describes the spread of the cancer into lymph nodes.
• M (metastasis) describes whether the cancer has spread to another part of the body.

What is stage 0 lung cancer?

The earliest stage of lung cancer, stage 0 is when the cancer is only present in the lining layer of the airways in the lung. It has not invaded deeper into the lung tissue.

What is stage 1 lung cancer?

Stage 1 lung cancer is also known as early or localised lung cancer. The cancerous tumour has not spread outside the lung, including to any lymph nodes. Stage 1A is 3 cm or smaller and stage 3B is 3-4 cm in size.

What is stage 2 lung cancer?

Stage 2 lung cancer is called locally advanced lung cancer - stage 2 NSCLC is sometimes called early stage NSCLC. Stage 2 lung cancer is divided into stage 2A and 2B: this depends on size and spread to other parts of the lung, to nearby lymph nodes, or to areas just outside the lung. The cancerous tumour can be of various sizes up to 7 cm.

What is stage 3 lung cancer?

Stage 3 lung cancer is also called locally advanced lung cancer, can be larger than 7 cm and may have spread further than stage 2. Depending on size and spread, it is divided into stages 3A, 3B and 3C.

The cancer has often spread to nearby lymph nodes. It may also have spread to other parts of the lung, the airway, surrounding areas outside the lung, or tissues and structures slightly further outside the lung, such as the windpipe or heart. However, the cancer has not spread to organs of the body that are further afield.

What is stage 4 lung cancer?

Stage 4 lung cancer, also known as metastatic or secondary lung cancer, is the most advanced stage of lung cancer. Depending on the extent of spread, it is divided into stage 4A and 4B.

The cancer can be of any size, and may have spread to lymph nodes as well as: the other lung, the tissue lining of the lung or the heart, or another part of the body like the liver, bones, or brain.

Your doctor will be able to explain about your stage of lung cancer in greater detail.

Further stages of small-cell lung carcinoma (SCLC)

If you have SCLC, your doctor may determine you as having one of these five stages, using the TNM system. They will then further class your lung cancer as either:

• Limited disease - the cancer has not spread beyond the lung.
• Extensive disease - the cancer has spread beyond the lung.

Further stages of non-small-cell lung carcinoma (NSCLC)

If you have NSCLC, the most common type of lung cancer, your doctor can also use the TNM system to describe your stage.

NSCLC is also typically given a clinical stage or pathologic stage:

• Clinical stage - based on the results of a physical exam, biopsy, and imaging tests.
• Pathologic stage - also called the surgical stage. If surgery is done, this stage is determined by examining tissue removed during the operation.

Staging for NSCLC can be complex, so it is important to ask your doctor to explain your particular lung cancer stage in a way that you can understand.

What are the treatment and survival outcomes of lung cancer stages?

Determining the stage of lung cancer is important, because it allows doctors to decide which treatments will give the best chance of survival.

According to the American Cancer Society, stage 0 NSCLC can be completely cured by surgery alone. Alternative treatments include photodynamic therapy (PDT), laser therapy, or brachytherapy (internal radiation). The main treatment for stage 1 and 2 is surgery to remove part or all of the lung. This may be followed with chemotherapy or radiation therapy to reduce the risk of the cancer returning.

Stage 3 may involve all three of these treatments, while stage 4 options include chemotherapy, radiation therapy, and immunotherapy. Targeted cancer drugs, which interfere with the growth of cancer cells, may be offered at stages 3 and 4.

Treatment of SCLC that's in the limited stage could involve aggressive treatments such as chemotherapy combined with radiation therapy. These treatments aim to remove the cancer completely. For extensive stage SCLC, chemotherapy is likely to be a better option. As in this stage the cancer has spread to other parts of the body, the aim of this treatment would be to control - and not cure - the cancer.