How Fast Does Lung Cancer Develop, Grow, and Spread?

Learn about doubling time and its role in progression and treatment

Many people wonder how fast lung cancer grows and how long it takes to spread. They also wonder about how long lung cancer takes to develop, or when it first started. The growth rate and doubling time of lung cancer are not just math questions, because they could affect treatment decisions in a new and evolving era of care. Some of these questions may include:

  • Is it okay to wait for genetic testing results before starting treatment?
  • Do you have time to do pulmonary rehabilitation before you have lung cancer surgery?
  • 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 the growth rate, may help answer those questions based on both the spread and recurrence of lung cancer. It will help to take some of the mystery out of what you can't see when cancer cells grow and spread.

lung cancer concept. doctor explaining results of lung check up from x-ray scan chest on digital tablet screen to patien
Prapass Pulsub / Getty Images

Every Cancer is Different

First, it's important to note that 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 they did, and you have reliable estimates for growth rate, you still need more information to make decisions about your lung cancer care.

One issue is the timing between a diagnosis and the start of treatment, and how that affects outcomes. In some cases, waiting a month for test results may lead to better outcomes than beginning treatment right away. That's especially true when targeted therapies are available for specific gene mutations.

Lung cancer growth rates are essential to know. But as cancer care becomes more personal, with cutting-edge treatments that target specific genetic changes, it's not the only thing to know. The type of lung cancer and other factors contribute to how cancer cells will grow and spread.

How Fast Lung Cancer Grows

The doubling time for lung cancer can help you to get an idea about proliferation, or how fast lung cancer cells grow. But it's important to look at the science of cancer cell growth, because there are limits to the math and the models used to estimate it. These limits mean that 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 normal lung cell becomes a cancer cell after a series of mutations in genes that control cell growth, often both oncogenes and tumor suppressor genes. This means the cell no longer works like a normal cell. The genetic changes do not usually all happen at once, but they add up as the cells divide into the billions over a period of time—sometimes decades. Even then, lung cancer still may be missed by a chest X-ray and the cells continue growing without anyone knowing.

Not All Cells Divide at the Same Time

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

Different types of cancer have different "growth fractions," a measure of the proportion of cells that are in an active cell cycle. Some cancers, such as childhood leukemias, have a very high growth fraction, meaning a large number of cells is dividing at a specific time. Other cancers, such as breast cancer, have a low growth fraction.

Growth Rate Varies at Different Stages

Tumor growth also may change during different stages in the life of the developing cancer cells. Tumors are not just copies of the exact same abnormal cells involved in out-of-control growth. The cells experience 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 in a tumor may cause cancer cells to grow and divide more rapidly than when it first began.

Specific Growth Rate

Researchers now often look at both tumor doubling time and specific growth rate to estimate how fast a tumor grows. Again, that's because the models used to estimate the doubling time may give results that are faster or slower than the real growth. The specific growth rate is calculated as the change in volume of a tumor in a certain period of time. The result is a percentage growth estimate in a defined time window, such as daily growth.

Recap

A key part of learning how lung cancers grow, and how long they might take to spread, is to first know how cancer cells work. Doctors look at the numbers—the growth fraction, the specific growth rate, the doubling time—to describe lung cancer in a standard way. But people are individuals, and the models don't always capture how fast or slow the cancer is in real life.

Lung Cancer Doubling Time

Doctors may describe the doubling of a lung tumor in terms of either volume or metabolic doubling time. What they mean is, how long it takes for it to double in size. But there are more limitations, similar to what we have already seen, when estimating doubling time from models. That's because:

  • The models assume a continuous rate of growth, and this is not the case.
  • It's hard to design studies in humans for ethical reasons. The results from animal or lab studies don't necessarily reflect what happens in people.
  • There are limits to estimating tumor size based on imaging, such as a CT scan.

Overall Doubling Time

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

Lung cancers, on average, double in size in four months to five months.

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 and any smoking history.

One study looked at growth rate by using CT scans taken an average of 25 days apart, followed by surgery to remove the tumors. The average doubling time was 191 days, with non-small cell tumors growing significantly slower than small cell lung tumors. Tumors in people who smoked had a more rapid doubling time than those from people who never smoked or had quit smoking. An important finding was that tumors with a slower doubling time (greater than 400 days) did not necessarily have a better prognosis, and 1/3 of people with these tumors developed metastases to distant regions of the body.

Doubling Time of CT-Detected Lung Cancer

A different study (the Pittsburgh Lung Screening Study) looked at the doubling time of CT-detected lung cancer, and separated the tumors into three categories:

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

They then compared these doubling times with subtypes. Lung adenocarcinoma (and the subtype of lung adenocarcinoma formerly referred to as bronchioloalveolar carcinoma) made up a significant proportion of the slow-growing group (86.7%) with only 20% in the rapid doubling time group. In contrast, squamous cell carcinoma of the lung made up 60% of the rapid doubling time tumors and only 3.3% of the slow doubling time group.

Squamous cell carcinoma of the lung tends to have a more rapid doubling time than lung adenocarcinoma.

Studies have also looked at the doubling time of adenocarcinomas that are EGFR positive, with some showing a longer doubling time and others not.

Doubling Time of Small Cell Lung Cancer

Doubling time with small cell lung cancer has been studied less than that of NSCLC, but appears to be both rapid and dependent on stage. Unlike NSCLC and its four stages, small cell lung cancer has only two stages: limited stage and extensive stage.

In a study looking at initial CT image scans, the average doubling time for small cell lung cancer 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 (24 days) when compared with limited stage disease (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

Looking at doubling times of tumors is helpful only if the estimated doubling times can be used to predict the growth of a person's tumor. One study looked at predicted survival times of people who had inoperable lung cancers (before recent advances in targeted therapies and immunotherapy) and found that there was a close correlation between survival predicted from doubling time and actual survival.

Survival Without Treatment

Researchers sometimes look to doubling time when asked a heart-wrenching question: How long can a person survive without treatment? Overall, it's thought that current models are not yet able to accurately estimate this answer.

Time to Spread (Metastasis)

Another common question concerns how long it takes lung cancer to spread (metastasize) to other regions of the body. Does a lung tumor have to first reach a certain size? Since metastases are the reason for most cancer deaths, this is an important question.

The answer is that it all depends. The speed at which lung cancer spreads may be tied closely with the type of lung cancer. While there are differences, it's important to note that any lung cancer (other than stage 0 lung cancer or noninvasive carcinoma in situ) has the potential to spread.

Any stage or size lung cancer has the potential to spread.

Overall, small cell lung cancer has the potential to spread very early. Even very tiny small cell lung cancers may spread to the brain or other organs, and these 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, even to lymph nodes. Lung adenocarcinomas appear to be somewhere in the middle.

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

Factors Other Than Growth Rate

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

Previously, it was thought that a tumor had to reach a certain size, first spread to lymph nodes, and then onward from there. We know now that this simply isn't the case. Instead, it may be specific mutations in the tumor, or the normal cells around it, that allow new cancer cells to grow in that organ or tissue.

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 break loose. Then they have to travel through either the blood, lymphatic system, or airways.

Spreading through the lymphatic system takes longer, but spread through the bloodstream can "seed" cancer cells to other parts of the body much faster and sometimes, long before the tumor is found. Tumor cells in the bloodstream are common even in very early-stage NSCLC.

Most of the cancer cells that arrive in a new body location will die off. For growth to occur, the cells need a blood supply (angiogenesis) as well as a change in the environment so that 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 new mutations that allow them to establish blood supply in a new region more easily, rather than growing in size and spreading via lymph nodes.

What this means is that it's important to catch cancers as early as possible to prevent spread or recurrence, but it's also important to find ways to prevent cells from setting up in other body sites.

An example of how this works is with the use of bisphosphonates for early stage breast cancer to lower the risk of recurrence. The drugs appear to work by changing the microenvironment of bone so that newly arriving cancer cells can't set up a home base and instead die off.

Time to Recurrence

How long will it take for lung cancer to recur? The size of a tumor at diagnosis and the number of positive lymph nodes are linked with the likelihood cancer will return, but they can't predict what will happen with individual people. Newer research is finding that how different the parts of a tumor are, or how much variety is present in the cells, may be linked with the cancer's ability to come back.

When Does Lung Cancer Begin?

A different question looks at when the lung cancer first began. People may think of a stressful time in their life, or a specific chemical exposure, and wonder if it could have been the "cause" of their cancer. There isn't a precise answer, but there are some theories.

One idea is to look at the patterns of mutation. A 2017 study published in the New England Journal of Medicine suggested that it takes a long time for a lung cancer to develop, perhaps decades, especially for lung adenocarcinomas.

When Can Lung Cancer First Be Detected?

Talk about doubling size raises the question of when lung cancer can first be detected. Lung cancer is most treatable in the early stages. Unfortunately, it's still the case that most people have an advanced-stage tumor when they are diagnosed.

It's thought that the average size at which lung cancers can be detected on a chest X-ray is 10 mm to 20 mm. But on chest CT, tumors as small as 6 mm (and sometimes as small as 4 mm) can often be seen.

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

Lung Cancer Screening Criteria

The U.S. Preventive Services Task Force recommends annual screenings using CT for people who:

  • Are 50 to 80 years old
  • Have a 20 pack-year history of smoking
  • Currently smoke or have quit smoking within the past 15 years
  • Are healthy enough overall to tolerate and benefit from treatment if diagnosed with lung cancer

Can Better Detection Mean a Cure?

With better screening, some people want to know if there's a certain tumor size that suggests the lung cancer can be cured. In 2017, researchers created a simulation model. They found that the most aggressive NSCLCs would need to be diagnosed at only 10 mm in size in males and 15 mm in females. The average size of a lung tumor at diagnosis without screening is 33 mm.

Summary

With the relatively new recommendation (especially with advanced lung adenocarcinoma) that results of genomic testing be evaluated prior to any treatment, concerns about the growth rate of lung cancer are likely to increase. Genomic testing results, whether done on tumor biopsy samples, a liquid biopsy, or both, can sometimes take up to two to four weeks.

Understanding the limitations of looking at growth rate, and how factors other than growth rate often play a role in tumor progression, may offer some reassurance during this waiting period.

A Word From Verywell

Outcomes (how a person does with the disease) are what is most important, and starting treatment right away without knowing the best treatment options can sometimes do more harm than good.

As more options are available and with cancer treatment changing so rapidly, 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.

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