How Fast Does Lung Cancer Grow? Understanding Doubling Time and Time to Spread

Lung cancer prompts many people to ask how fast it grows and how long it takes to spread. This also raises the question of when it began. The issue is more than a mathematical problem: growth rate can influence treatment decisions and approaches. Important questions therefore include whether to wait for genetic testing results or begin treatment immediately, and whether to monitor a lung nodule or intervene at once. This article answers common questions about lung cancer growth and spread while considering important factors beyond growth rate.

Every Cancer Is Different

Just as every person is different, so is every cancer. Even two lung cancers of the same type and stage may behave very differently at the molecular level. Not all cancers grow at the same rate. Even a reliable prediction of how quickly one will grow is not enough: more information is needed. Every treatment decision depends on multiple factors.

The time between diagnosis and treatment can affect outcomes. In some cases, starting immediately may not be the right choice. When a particular gene mutation can be targeted, waiting 3-4 weeks for test results may lead to a better outcome.

Understanding growth rate is important but may not be enough. Other factors indicate how cancer may grow and spread, including its subtype.

How Quickly Does Lung Cancer Grow?

Proliferation describes how quickly lung cancer cells grow.

Doubling time is the time it takes for a tumor to double in size.

Doubling time can help explain how quickly cancer grows. In general, lung cancers double in size on average every four to five months.

The most important determinant of doubling time is whether the tumor is small cell lung carcinoma (SCLC) or non-small cell lung carcinoma (NSCLC).

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

NSCLC doubling time may vary with factors such as:

• Cancer Subtype: NSCLC has at least 4 subtypes: adenocarcinoma, squamous cell carcinoma, large cell carcinoma and NOS (not otherwise specified).
• A history of smoking

One study used computed tomography (CT) scans taken an average of 25 days apart to assess tumor growth. The tumors were then removed surgically.

It found that average tumor doubling time was 191 days . Non-small cell tumors grew significantly more slowly than small cell tumors. Tumors in smokers doubled faster than those in people who had never smoked or had quit.

Interestingly, patients with tumors whose doubling time exceeded 400 days did not necessarily have a better prognosis. In one third of them, cancer had spread to distant parts of the body.

Another study examined doubling time in CT-detected lung cancer, dividing tumors into three categories:

• Fast-growing, doubling in less than 183 days: 15.8%
• Typical/normal, doubling in 183 to 365 days: 36.5%
• Slow-growing, doubling in more than 365 days: 47.6%

Researchers compared these doubling times with subtypes. In the slow-growing group, 86.7% had lung adenocarcinoma. Only 20% of patients with these subtypes were in the fast-doubling group.

By contrast, 60% of the fast-growing group had squamous cell lung carcinoma, while only 3.3% of the slow-growing group had this subtype.

Research has also examined doubling time in EGFR-positive adenocarcinomas. Most people with this lung cancer mutation have little or no smoking history. Findings have been mixed, with some studies showing a longer doubling time and others not.

Doubling Time in Small Cell Lung Cancer

NSCLC has 4 stages, while small cell lung cancer is classified into 2:

• Limited-stage disease, confined to the thorax (chest), and
• Extensive-stage disease, spread to other parts of the body.

Doubling time in small cell lung cancer is less well studied than in NSCLC. It appears both rapid and stage-dependent.

A 2012 study examined initial CT scans in people with small cell lung cancer. Average doubling time was 70 days for the primary tumor and 51.1 days for involved lymph nodes. It was much faster in extensive-stage than limited-stage disease: 24 versus 97.6 days.

Factors Affecting Growth Rate

Several factors may influence lung cancer growth, including:

• The main type (NSCLC or SCLC) and subtype
• Genetic mutations, such as EGFR
• Smoking status
• Differences between men and women
• Techniques used to diagnose the tumor

Different subtypes can grow at different rates. Other factors, such as smoking history, also play a role.

Predictions Based on Doubling Time

Tumor doubling time is useful in predicting growth. One study examined estimated survival in people with inoperable lung cancer and found that doubling time could help predict survival.

Predictions for an Untreated Patient

Researchers sometimes use doubling time to estimate how long a person might live without treatment. Current models are generally thought unable to answer this accurately.

Time to Metastasis (Spread)

Patients also want to know how long lung cancer takes to spread elsewhere in the body. This is called metastasis . Since 90% of cancer-related deaths are due to metastases, this is an important question.

Although there are differences, almost every lung cancer type can potentially spread. The exception is stage 0 lung cancer, or noninvasive carcinoma in situ.

Small cell lung cancer can spread very early, even to the brain or other organs at an early stage. Brain-related symptoms are often the first sign of SCLC.

By contrast, squamous cell lung carcinomas may become quite large before spreading. Some have reached 8-10 cm without metastasizing.

The most common sites of lung cancer metastases are generally:

• Bone (34.3%)
• The other lung (32.1%)
• Brain (28.4%)
• Adrenal glands (above the kidneys; 16.7%)
• Liver (13.4%)

Factors Other Than Growth Rate

A tumor's likelihood of metastasizing generally depends on factors other than growth rate or doubling time.

It was once thought that tumors had to reach a certain size and spread first to lymph nodes, then elsewhere. We now know that this is not necessarily the case. Tumors may instead carry particular mutations that help them spread. Speed also depends on how cells travel through the body.

First, cancer cells must escape both their original location and the immune system . Normal cells have molecules that hold them together; mutations in cancer cells may make separation easier or harder. They must then travel through blood, the lymphatic system or airways.

Lymphatic spread takes longer. The bloodstream, however, can "seed" cancer cells elsewhere much faster, sometimes long before the tumor is found. Tumor cells are commonly present in the blood even in very early SCLC.

Most cancer cells die at a new destination. To grow, they need a blood supply, through angiogenesis . The environment must also change so the immune system does not attack them, requiring communication with normal cells. Some lung cancer cells may develop mutations that make these processes easier.

Finding ways to prevent cells from settling elsewhere is therefore important. In early-stage breast cancer, for example, bisphosphonates can reduce recurrence risk. These bone-protective drugs alter the bone microenvironment, attempting to prevent newly arriving cancer cells from establishing themselves.

Time to Recurrence

Tumor size at diagnosis and the number of positive lymph nodes are associated with recurrence risk, but cannot predict what will happen to an individual. New research suggests that cellular diversity or differences within parts of a tumor may affect its ability to recur.

When Does Lung Cancer Begin?

Many patients wonder when their cancer began. They may associate it with a stressful period or a particular chemical exposure, but there is no clear answer.

A 2017 study suggested that lung cancer development may be lengthy, potentially taking decades. This may particularly apply to adenocarcinomas, which originate in the lung's glands. A cancer may therefore have begun decades before diagnosis. Linking it to a specific event or period is usually difficult, with multiple interacting factors generally involved.

Lung cancer often causes no symptoms early on; symptoms usually appear as it progresses. It is therefore often detected at an advanced stage. Early lung cancer is generally an incidental finding or detected during scans for something else.

In high-risk individuals, low-dose computed tomography (CT) can detect early lung cancer. Specific risk factors are required for this screening.

Lung cancer is therefore often diagnosed at an advanced stage, affecting treatment options and overall prognosis.

Growth rates depend on multiple factors, and every patient's experience differs. Patients should discuss these factors and their effect on treatment options with their doctor. A rapidly growing tumor may require a more aggressive approach, for example, while a slower-growing one may call for a different strategy.

Summary

Lung cancer spreads at different speeds in different patients. Doubling time offers important information but is not the only factor predicting growth.

Different subtypes grow at different rates, influenced by factors such as genetic mutations and smoking history. Some cancer types may be more capable of spreading to distant sites.

CT can detect lung cancer early. If smoking places you in a high-risk group, discuss screening with your doctor.

A Final Word

Newly diagnosed patients now generally undergo genomic testing before treatment. Waiting for results, which can sometimes take two to four weeks, may make them worry that the cancer will spread.

The course of disease, or how a person copes with it, matters most. Starting treatment immediately without knowing the best options may sometimes do more harm.

Cancer treatment is changing rapidly, with many new options. Finding a doctor you trust is important. Another way to learn about your disease is to contact specialists or people with similar experience who can offer support as you face uncertainty.