How Fast Does Lung Cancer Grow?

Many people wonder how fast lung cancer grows and how long it takes to spread. They also wonder how long lung cancer takes to develop, or when it first started.

The growth rate of lung cancer is not just a math question. It could affect treatment decisions in a new and evolving era of care. Some of these questions may include:

• Should you wait for genetic testing results before starting treatment?
  
• If a lung nodule is found during screening, is it OK to wait and watch it for the time being?
• Does the size of your cancer mean it's more likely to spread or come back?

This article explores how other key factors besides growth rate may help answer common questions about lung cancer growth and spread.

Every Cancer Is Different

Every person is different, and so is every cancer. Even two lung cancers of the same type and stage may behave quite differently at the molecular level.

Not every cancer grows at the same rate. Even if it did, and you were able to reliably estimate how fast your cancer would grow, you would still need more information. Each care decision is made based on multiple factors.

The timing between diagnosis and start of treatment can affect outcomes. In some cases, starting treatment right away may not be the right choice. It's possible to have a better outcome if you wait a month for test results instead. That's especially true if there's a specific gene mutation that can be treated with targeted therapy.

How Fast Lung Cancer Grows

Proliferation describes how fast lung cancer cells grow. Doubling time is the amount of time it takes a tumor to double in size.

The doubling time can help you understand how fast your cancer will grow, but it's also important to look at the science of cancer cell growth. Unfortunately, there are limits to the math and models used to estimate cancer growth. This means estimates of the true growth rate may be far too high or too low. In other words, there is no simple formula.

The Science of Lung Cancer Cell Growth

A cancer cell no longer works like a normal cell. A normal lung cell becomes a cancer cell after a series of mutations in genes that control cell growth.

The genetic changes don't usually all happen at once. They add up as the cells divide into the billions over a period of time. This process sometimes takes decades. Even then, lung cancer still may be missed by a chest X-ray.

Not All Cells Divide at the Same Time

Growth rates and doubling time matter, but there are exceptions to every rule. Cancer growth estimates are based on exponential growth. For example, one cell becomes two, two become four, four then become eight, and so on. In real life, however, not all cells divide at the same rate and at the same time.

Different types of cancer have different "growth fractions." Some cancers, such as childhood leukemias, have a very high growth fraction. This means a large number of cells are dividing at a specific time. Other cancers, like breast cancer, have a low growth fraction.

Growth Rate Varies at Different Stages

Tumor growth may also change during different stages in the life of the cancer cells. Tumors are not just copies of the cells involved in out-of-control growth. There may be new mutations that change the tumor. Many people see this when new mutations make their cancers resist treatment that worked in the past. Some of the new mutations may cause cancer cells to grow and divide faster than the early cancer did.

Specific Growth Rate

Growth rate is the percent change in a tumor's volume over a certain period of time, such as daily. Researchers use both growth rate and doubling time to help estimate how fast a tumor will grow. Again, that's because the models used to estimate doubling time may give results that are faster or slower than the real growth.

Lung Cancer Doubling Time

Doctors may describe the doubling of a lung tumor in a couple of ways:

• Volume doubling time
• Metabolic doubling time

This just describes how long it takes the tumor to double in size. As we've seen, though, there are limits to the models used to estimate doubling time. That's because:

• The models assume a continuous rate of growth, but tumors don't grow like that.
• It's hard to design studies in humans for ethical reasons. The results from animal or lab studies don't always reflect what happens in people.
• It's hard to estimate tumor size based on imaging.

Overall Doubling Time

Some studies have looked at the doubling time of lung cancer in people with different types and stages of the disease. One study compared the doubling time of breast cancer with that of non-small cell lung cancer (NSCLC). It found that the volume doubling time for lung cancer was 134 days. This was significantly faster than breast cancer, which was 252 days.

Doubling Time of Non-Small Cell Lung Cancer (NSCLC)

The doubling time of non-small cell lung cancer can vary based on several factors, including:

• The subtype of cancer
• Smoking history, if any

One study used computerized tomography (CT) scans taken an average of 25 days apart to look at growth rate. This is a imaging procedure that takes multiple X-rays and combines them into a detailed image of an internal structure. After the scans, the patients had surgery to remove the tumors.

The study found that the average doubling time was 191 days. Non-small cell tumors grew significantly slower than small cell lung tumors. Tumors in people who smoked had a faster doubling time than those in people who never smoked or had quit smoking.

An important finding was that patients who had tumors with a doubling time of more than 400 days did not necessarily have a better prognosis. In a third of patients with these tumors, the cancer spread to distant parts of the body.

A different study also looked at the doubling time of CT-detected lung cancer. Researchers put the tumors in three categories:

• Rapid growing, with a doubling time of less than 183 days: 15.8%
• Typical, with a doubling time of 183 to 365 days: 36.5%
• Slow growing, with a doubling time of over 365 days: 47.6%

They then compared these doubling times with subtypes. They found that 86.7% of patients in the slow-growing group had lung adenocarcinoma or a subtype formerly called bronchioloalveolar carcinoma. Only 20% of patients with these subtypes were in the rapid doubling group.

In contrast, 60% of patients in the rapid doubling group had squamous cell carcinoma of the lung. Only 3.3% of patients in the slow doubling group had this subtype.

Studies have also looked at the doubling time of adenocarcinomas that are EGFR positive. Most people who have lung cancer with this mutation have little or no history of smoking. These studies have had mixed findings, with some showing a longer doubling time and others not.

Doubling Time of Small Cell Lung Cancer

NSCLC has four stages, but small cell lung cancer has only two stages: limited stage and extensive stage.

Doubling time with small cell lung cancer has not been as well studied as that of NSCLC. It does appear to be both rapid and dependent on stage.

A 2012 study looked at initial CT image scans in people with small cell lung cancer. The average doubling time was 70 days for the primary tumor, and 51.1 days for affected lymph nodes. The doubling time was much faster with extensive stage disease than it was in limited stage disease. Extensive stage disease had a doubling time of 24 days while limited stage was 97.6 days.

Factors That Affect Growth Rate

There are a number of factors that may affect the growth rate of lung cancer, including:

• The type and subtype of lung cancer
• Genetic mutations, like EGFR
• Smoking status
• Differences between men and women
• Techniques used to diagnose the tumor

Predictions Based on Doubling Times

Tumor doubling time is helpful when it can be used to predict the growth of a tumor. One study looked at the predicted survival times of people with inoperable lung cancer. It found that doubling time could be used to predict survival times.

Survival Without Treatment

Researchers sometimes look at doubling time to estimate how long a person might survive without treatment. Overall, it's thought that current models aren't able to accurately answer this question.

Time to Spread (Metastasis)

Patients also want to know long it takes lung cancer to spread to other parts of the body. This is called metastasis. Since metastases are the reason for most cancer deaths, it's an important question.

The answer is that it depends. The speed that cancer spreads may be tied closely with the type of lung cancer. While there are differences, it's important to note that almost any lung cancer can potentially spread. An exception is stage 0 lung cancer or noninvasive carcinoma in situ.

Small cell lung cancer can spread very early. Even very tiny small cell lung cancers may spread to the brain or other organs. In fact, brain-related symptoms are often the first sign of the disease.

Squamous cell carcinomas of the lung, however, may be quite large before they spread. Lung adenocarcinomas appear to be somewhere in the middle.

Overall, the most common sites of lung cancer metastases include:

• Bone (34.3%)
• Lung (32.1%)
• Brain (28.4%)
• Adrenal glands (16.7%)
• Liver (13.4%)

Factors Other Than Growth Rate

The chance that a tumor will spread often depends on factors other than the growth rate or doubling time.

It was once thought that a tumor had to reach a certain size before it could spread. Researchers also believed it would spread to lymph nodes first, then onward from there. We now know this isn't the case. Instead, tumors may have specific mutations that help them spread. The speed can also depend on how the cells travel through the body.

First, the cancer cells need to "escape." Normal cells have molecules that hold them together. Different mutations in cancer cells can make it easier or harder to for them to break loose. Then they have to travel through either the blood, lymphatic system, or airways.

It takes longer for cancer to spread through the lymphatic system. The bloodstream, however, can "seed" cancer cells in other parts of the body much faster. Sometimes this can happen long before the tumor is found. Tumor cells in the bloodstream are common even in very early-stage NSCLC.

Most of the cancer cells die when they arrive in a new location. For growth to occur, the cells need a blood supply, called angiogenesis. They also need a change in the environment so the immune system doesn't attack them. To do this, they need to communicate with normal cells nearby. It could be that some lung cancer cells develop mutations that let them do these things more easily.

This means it is important to find ways to prevent cells from setting up in other body sites. In early stage breast cancer, for example, bisphosphonates can lower the risk of recurrence. These drugs appear to work by changing the microenvironment of bone. The newly arriving cancer cells can't set up a home base and instead die off.

Time to Recurrence

The size of a tumor at diagnosis and the number of positive lymph nodes are linked with the likelihood cancer will return. They can't predict what will happen with individual people, though. Newer research is finding that cell variety or differences in the parts of a tumor may affect its ability to recur.

When Does Lung Cancer Begin?

Many patients want to know when their cancer first began. You may wonder if a stressful time in your life or specific chemical exposure "caused" your cancer. There isn't a good answer to this question.

A 2017 study suggested that it takes a long time for a lung cancer to develop, perhaps decades. This may be especially true for lung adenocarcinomas.

When Can Lung Cancer First Be Detected?

Lung cancer is most treatable in the early stages. Unfortunately, most people have an advanced-stage tumor when they are diagnosed.

It's thought that chest X-rays can't find lung cancer until it's 10 mm to 20 mm in size. A chest CT, though, may find tumors as small as 6 mm, sometimes 4 mm.

The difference is clear. Medical providers now know that screening chest X-rays don't save lives, but screening chest CT scans clearly do.

Can Better Detection Mean a Cure?

With better screening, some people want to know if smaller tumors can be cured. In 2017, researchers created a simulation model to help answer this question. They found that in males, the most aggressive NSCLCs would need to be diagnosed 10 mm in size. In females, the diagnosis would need to be made at 15 mm. Without screening, the average size of a lung tumor at diagnosis is 33 mm.

Summary

The rate that lung cancer spreads is different for every patient. Doubling time can provide important information, but it isn't the only thing that can predict growth rate.

Different subtypes of lung cancer may grow at different rates. Growth rates can also depend on factors like genetic mutations and history of smoking. Some cancers may also be better at spreading to distant parts of the body. 

Lung cancer can be caught early on a CT scan. If you're in a high risk group, talk to your doctor about lung cancer screening.

A Word From Verywell

Today, genomic testing is often done before newly diagnosed patients begin treatment. This may make patients worry that their cancer will spread while waiting for results, which can sometimes take two to four weeks.

Outcomes, or how a person does with the disease, are what is most important. Starting treatment right away before knowing the best treatment options can sometimes do more harm than good.

Cancer treatment is changing rapidly, and many new treatment options are available. This is why it's important to find a doctor you trust. Another way to learn about your disease is to connect with the lung cancer community and get support while facing uncertainty.