After receiving a lung cancer diagnosis, you may want to learn as much as you can about how it affects your outlook (prognosis). Researchers have found that your primary (main) tumor size may affect your survival with lung cancer. Tumor size is one of many prognostic factors — aspects of your lung cancer that affect your prognosis.

In this article, we’ll cover how lung cancer tumor size is used to predict survival. To learn more about your individual outlook with lung cancer, talk to your doctor. They’ll help you understand all the factors involved in understanding survival.

How Is Lung Tumor Size Measured?

Oncologists (cancer specialists) usually diagnose lung cancer with a combination of tests. Imaging studies help your oncologist measure how large the lung tumor is.

Computed tomography (CT) scans use X-rays to take pictures of your body at different angles. Computer software combines the pictures to create a 3D image of your lungs and the tumor. According to the American Clinical Society of Oncology (ASCO), oncologists use these images to measure the tumor’s size.

Magnetic resonance imaging (MRI) can also be used to measure lung tumor size. However, it’s not the most effective method for taking pictures of organs that move — like your lungs when you breathe. Your oncologist is more likely to order a CT scan instead.

Tumor Size and Lung Cancer Staging

Lung cancer staging is a large part of how oncologists predict outcomes. In non-small cell lung cancer (NSCLC), oncologists use the American Joint Committee on Cancer TNM staging system. The “T” stands for the size and extent of the primary tumor. Your oncologist will use your tumor measurements when staging your disease.

However, cancer staging is a complex process that involves many factors. The TNM system also accounts for any lymph node involvement (“N”) and whether the cancer has spread or metastasized (“M”). Together, these three factors give your NSCLC stage.

For each part of the TNM system, oncologists can assign numbers and letters to describe NSCLC even further. For example, a T1a tumor is no more than 1 centimeter across. A T1b tumor is between 1 and 2 centimeters across, while a T1c tumor is between 2 centimeters and 3 centimeters.

The American Cancer Society notes that each size as part of the “T” is associated with a different TNM stage:

• Stage 0 — The tumor isn’t large enough to measure.
• Stage 1 — The tumor is between 0.5 centimeters and 4 centimeters across.
• Stage 2 — The tumor is between 3 centimeters and 7 centimeters across.
• Stage 3 — Some tumors may be smaller than 3 centimeters across, while others are larger than 7 centimeters across.
• Stage 4 — The tumor is any size.

When oncologists stage small cell lung cancer (SCLC), they usually don’t use the TNM system. Instead, they use a two-stage system to note how far the cancer has spread. Tumor size usually isn’t factored into staging SCLC.

Studies Show Lung Tumor Size Can Predict Survival

Researchers have conducted studies looking at how tumor size may predict survival with lung cancer. A report on people with advanced NSCLC found that tumor size affects median overall survival (OS). This refers to the amount of time at which half of people in a study are still alive.

The report showed that the median OS for NSCLC tumors that were smaller than 7.5 centimeters was 12.6 months. For those with tumors 7.5 centimeters or larger, the median OS was 9.5 months. This means that smaller NSCLC tumors were associated with better survival.

Another study of more than 52,000 people with NSCLC looked at the effect of tumor size on overall survival. The researchers looked at tumor size based on how large the tumors were and which lung tissues were affected. They found that tumor size significantly affected OS, especially in early-stage lung cancer.

Your Lung Cancer Stage Helps Predict Survival

Your oncologist can use your tumor stage as a predictor for survival. Tumor size is just one part of the staging system. Your oncologist will also take into account where the tumor is located in the lung and whether it’s blocking other important structures.

When talking about survival with cancer, doctors often use the term five-year relative survival rate. This rate compares the survival rate of people with lung cancer to that of the general population. A five-year relative survival rate of 50 percent means that people with lung cancer are 50 percent as likely to be alive after five years compared to the general population.

Data collected by the National Cancer Institute (NCI) show that lower relative survival rates are associated with more advanced stages of lung cancer. The NCI uses a different staging system that notes how far your cancer has spread. It can also take into account your lung tumor size. It’s important to note that these data are based on previous studies and can’t predict your exact survival or outcome.

Response to Tumor-Shrinking Treatment Before Surgery Also Predicts Survival

Oncologists are always looking for ways to improve outcomes with lung cancer. When lung tumors are too large to operate on, oncologists can use treatments to shrink them first. This is known as neoadjuvant therapy.

Oncologists use several treatments for neoadjuvant therapy, including:

• Radiation therapy, which uses concentrated X-rays to kill tumor cells
• Chemotherapy, which uses toxic chemicals to kill rapidly dividing cells, including tumor cells
• Immunotherapy, which activates your immune system to target and destroy tumor cells

A 2023 study found that response to neoadjuvant treatment with chemotherapy and immunotherapy can predict survival with lung cancer. Researchers measured how much of the lung tumor was left behind after treatment and compared it to event-free survival (EFS). This term refers to the amount of time after a treatment that your cancer doesn’t grow or return.

The researchers found that the more a person’s primary tumor shrunk after treatment, the better EFS they had. For example, people who had 0 percent to 5 percent of their lung tumor left had a two-year EFS rate of 90 percent. This means that after two years, 90 percent of people in that group didn’t have their cancer grow or return.

On the other hand, people with more than 80 percent of their lung tumors left after neoadjuvant treatment had a two-year EFS rate of 39 percent. This means that more people had their cancer grow or return.

Researchers Continue Looking for New Ways To Predict Survival

As science continues advancing, researchers keep looking for new and better ways to measure tumor size. The hope is that these tools will help doctors better predict survival with lung cancer.

One study looked at different ways of imaging lung tumors using CT scans to find the best one for measuring size. By getting more accurate size measurements, oncologists can correctly stage and treat lung cancer to improve survival.

Talk With Others Who Understand

On MyLungCancerTeam, the social network for people with lung cancer and their loved ones, more than 12,000 people from around the world come together to ask questions, offer support and advice, and connect with others who understand life with lung cancer.

Do you still have questions about how your lung cancer tumor size plays a role in predicting survival? Share your story and tips in the comments below or by posting on your Activities page.