Guide to Lung Cancer TNM Staging

Technician examining diagnostic image
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If you're trying to figure out the stage of your lung cancer you might be feeling very confused. What does it mean when your oncologist talks about "TNM" and how is this correlated with the stages? Let's take a look at the meaning of each of these letters, how doctors use these to stage cancer, and what that ultimately means in terms of treatment.

The TNM System

TNM staging for lung cancer can be confusing for anyone to understand, let alone someone who has just been hit with the news of a lung cancer diagnosis. How does TNM staging align with the lung cancer stages, like stage 2 and stage 4?

What the Letters Mean

Each of the TNM letters stands for the size or spread of cancer as follows:

  • T – Stands for the size of the tumor. Tumor size is usually given in centimeters (cm). To understand this in inches, 5 cm is about the same as 2 inches.
  • N – N stands for lymph nodes and tells whether the tumor has spread to lymph nodes, and if so, how far away from the tumor they are.
  • M – M stands for metastasis, that is, the spread of the tumor to other parts of the body.

Why Staging Is Important

TNM staging helps doctors understand how extensive cancer is and, therefore, what the best treatment options are for that particular cancer. It can also help predict what the average prognosis is for someone with lung cancer. TNM staging is based on worldwide data on lung cancer in thousands of people and compares the extent of lung cancer with responses to treatment and prognosis.

That said, it is very important to understand that there are many factors that affect the prognosis of lung cancer that go beyond the stage. Your general health, the particular type of lung cancer you have, whether or not you have "targetable" gene mutations in your tumor, and even your gender can play a role in what treatments will work best for you and what your individual prognosis may be.

TNM Staging Breakdown

You will notice that your TNM letters will have numbers that follow them. Let's look at what the different numbers mean:

T - Tumor Size

  • Tx – The tumor size is unknown, or cancer cells are only found in sputum.
  • T0 – There is no evidence of a primary tumor.
  • TisCarcinoma in situ – The tumor is present only in the cells lining the airway and has not spread to nearby tissues.
  • T1 – Tumors less than or equal to 3 cm (1 1/2 inches).
    • T1a – Less than or equal to 2 cm.
    • T1b – Greater than 2 cm but less than or equal to 3 cm.
  • T2 – The tumor is greater than 3 cm but less than 7 cm. T2 tumors may block part of the airway, but have not resulted in pneumonia or caused the lung to collapse (atelectasis). They may have spread to the lining around the lungs. They may also be close to the main bronchus but are at least 2 cm (about an inch) away from the area in which the bronchus divides to go to each of the lungs.
    • T2a – Greater than 3 cm but less than or equal to 5 cm.
    • T2b – Greater than 5 cm but less than or equal to 7 cm.
  • T3 – Tumors greater than 7 cm, or less than 7 cm but with a separate nodule in the same lobe. T3 tumors also include tumors that are less than 7 cm but invade the lining of the lung (pleura), the chest wall, the diaphragm, the main bronchus, or lie within 2 cm of the area where the bronchus divides to travel to the lungs. A tumor is also classified as T3 if it is less than 7 cm but is associated with pneumonia or the collapse of the entire lung.
  • T4 – A tumor of any size, but with another nodule in a different lobe on the same side of the body, or a tumor that invades structures in the chest such as the heart, major blood vessels near the heart, the trachea, the recurrent laryngeal nerve (a nerve near the trachea), the mediastinum (the space between the lungs), the esophagus, or the area where the main bronchus divides to travel to the two lungs.

N – Involvement of Lymph Nodes

  • N0 – No nodes are involved.
  • N1 – The tumor has spread to nearby nodes on the same side of the body.
  • N2 – The tumor has spread to nodes farther away but on the same side of the chest.
  • N3 – The tumor has spread to lymph nodes on the other side of the chest from the original tumor, or has spread to nodes near the collarbone or neck muscles.

M – Metastasis (Spread) to Other Regions

  • M0 - The tumor has not spread to distant regions.
  • M1
    • M1a – The tumor has spread to the opposite lung, to the lung lining (malignant pleural effusion) or has formed nodules on the pleura.
    • M1b – The tumor has spread to distant regions of the body, such as the brain or bones.

Comparison of Lung Cancer Stages and TNM Staging

Most people are more familiar with the stages of lung cancer than they are with TNM staging. Here is a comparison of lung cancer stages and TNM staging:

  • TisN0M0
  • Stage 1A Lung Cancer
    • T1aN0M0
    • T1bN0M0
  • Stage 1B Lung Cancer
    • T2aN0M0
  • Stage 2A Lung Cancer
    • T1aN1M0
    • T1bN0M0
    • T2aN1M0
  • Stage 2B Lung Cancer
    • T2bN0M0
    • T2bN1M0
    • T3N0M0
  • Any T, Any N, M1a
  • Any T, Any N, M1b

Newly Diagnosed With Lung Cancer

If you have just been diagnosed with lung cancer, you're probably feeling both frightened and overwhelmed. You may have heard that knowing as much as possible about your cancer may improve outcomes, but how can you do that when everything seems to be written in a foreign language?

Take time to educate yourself. Talk to your doctor and ask a lot of questions. Learn how to find good cancer information online. Many people with lung cancer consider getting a second opinion, and this is very important. It's often recommended that you make this second opinion at one of the larger National Cancer Institute-designated cancer centers where there are likely to be oncologists who specialize in your particular type of lung cancer. Also, if you have non-small cell lung cancer, make sure your doctor has ordered gene profiling (molecular profiling) of your tumor.

Make sure to be your own advocate for your cancer care. To do this, it can be helpful to become connected to the lung cancer community online (the hashtag is #LCSM). These communities not only lend support but can help you learn and navigate your way through the multitude of choices you will be facing.

Most of all, hang on to hope. The treatments for lung cancer are improving, and the survival rates are improving as well. There have been more new treatments approved for lung cancer in just the past few years than in the decades before.

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