COPD & Lung Cancer: What's the Connection and How Can You Reduce Your Risk?
COPD is a complicated disease that comes with a variety of extraneous health concerns, including an increased risk for several other serious diseases. One of those diseases is lung cancer, a condition that is quite different from COPD, but still linked to the chronic lung disease in numerous ways.
Research shows people who have COPD are about twice as likely to develop lung cancer than people who don't have COPD. Unfortunately, research suggests that the vast majority of people with COPD have no idea about this increased lung cancer risk.
This lack of awareness is dangerous, because unaware COPD patients may be less likely to take important cancer-prevention measures or watch for lung cancer symptoms. This can result in fewer lung cancer screenings, later lung cancer diagnoses, and fewer efforts among COPD patients to make healthy lifestyle changes that could lower their lung cancer risk.
In this post, we're going to take a closer look at why there's such a strong connection between these two deadly lung diseases, including what factors tie them together and what sets them apart. We'll also discuss what this elevated risk for lung cancer means for people with COPD, explaining what types of lung cancers you might be at risk for and what you can do, specifically, to reduce your future lung cancer risk.
Lung Cancer and COPD: Fundamentally Different Yet Fundamentally Linked
At first, it might seem strange that lung cancer and COPD are linked at all, especially when they are such vastly different types of diseases. After all, COPD is a chronic, lifelong illnesses and cancer is, well... cancer! And we often tend to think about cancer as a unique type of disease in a category all on its own.
But, while it's true that lung cancer and COPD are fundamentally different diseases, they actually have many characteristics in common—aside from the fact that they both affect the lungs. For example, both diseases can cause very similar breathing symptoms and they even share many of the same risk factors and causes.
But to understand why having COPD increases your risk for lung cancer, you'll first need some basic knowledge about both of these diseases and how they work. Then, we can take a closer look at some key similarities and differences between lung cancer and COPD that can shed some light on how they're connected.
In the next few sections, we'll explain everything you need to know about lung cancer and COPD to get the most out of this guide, including what causes both diseases, how they develop, and how their progression compares.
Then, we'll jump right into discussing how the diseases are linked before giving you some helpful, science-based tips for how to reduce your risk for lung cancer if you have COPD.
The Basics of Lung Cancer vs COPD
Lung cancer is a deadly disease caused by cancerous cells and tumors growing inside the lungs. It is the leading cause of cancer deaths in the US, killing more people than breast cancer, prostate cancer, and colorectal cancer combined; however, lung cancer can be cured with proper treatment in some cases, especially if you catch it early on.
By contrast, COPD is a chronic, lifelong disease that can be treated, but not cured. It is largely caused by damage and inflammation in the lung tissues and airways that makes it more and more difficult to breathe as the disease progresses.
Lung cancer begins as soon as cancerous cells appear in the lungs, though it can take some time before the cancer is detectable or the first symptoms start to appear. COPD, on the other hand, often doesn't have a clear beginning, as it is the result of chronic lung inflammation that occurs over the course of many years.
Most of the time, COPD is caused by smoking and long-term exposure to respiratory irritants like secondhand smoke and air pollution. Smoking is also the number one cause of lung cancer, though other respiratory irritants and carcinogenic substances (e.g. asbestos and radon gas) can also cause lung cancer, especially if you are exposed to them repeatedly over time.
How Cancerous Mutations Take Over Your Lungs
Cancerous lung cells start as normal lung cells that become cancerous after acquiring certain types of DNA mutations. However, not all cell mutations are cancerous; some mutations are harmless, while others get corrected (or the whole cell gets destroyed) before they cause any problems.
So what is it exactly that makes a cancer cell different—and more dangerous—than a cell with a non-cancerous mutation or a healthy, normal cell? The answer is that cells only become cancerous when they develop several specific types of mutations that cause the cell to stop following certain “rules.”
In particular, cancer cells have mutations that allow them to multiply freely and ignore the usual controls that constrain how and when cells divide. They also have mutations that allow them to escape the body's natural defenses that would otherwise repair or destroy these mutated cells.
These cancerous cells are dangerous because the body can't detect and destroy them on its own; this allows the cancer cells to multiply out of control and spread to places they're never supposed to be. Eventually, these rogue cells begin to interfere with normal biological functions, though their exact effects depend on where the cancer is located and what types of mutations the cancer cells have.
Carcinogens and Lung Cancer
One thing that's important to know about cell mutations is that they can happen essentially by chance. They can happen any time a cell multiplies, or any time a cell's DNA gets copied, duplicated, or repaired.
However, some things—known as carcinogens—can cause a significant increase in DNA mutations. More mutations means a higher risk for cancer, since it creates more opportunities for a cancerous mutation to occur.
Some carcinogens, like UV radiation from sunlight, can mutate DNA directly by striking the DNA molecules or triggering a chemical reaction that damages DNA inside a cell. Other carcinogens, like tobacco smoke, indirectly mutate DNA by causing repeated inflammation and injury that damages DNA both in the cells it touches and in the surrounding tissues that get inflamed.
In general, your risk for cancer gets higher the more frequently you're exposed to cancer hazards. It's kind of like rolling a dice; your chances of developing a cancerous mutation on any given roll is very low, but the more times you roll the dice, the more likely you are to “roll” a cancerous mutation eventually.
Different Diseases, Similar Symptoms
As we explained in the section above, lung cancer happens via a completely different biological mechanism than COPD. However, both diseases directly affect the lungs' ability to function, which means both diseases can cause some of the same respiratory symptoms.
COPD causes breathing symptoms because the damage it does to your lungs and airways restricts airflow to the lungs and reduces how much oxygen they can absorb. Lung cancer causes cancer cells to spread across healthy lung tissue and/or form tumors on the lungs, which interferes with normal functions and makes it more difficult to breathe.
Symptoms of COPD:
- Shortness of breath
- Difficulty breathing
- Chronic cough (especially a wet cough that produces phlegm)
- Chest tightness
- Frequent respiratory infections
- Swelling in legs, ankles, or feet
Unexplained weight loss (in the advanced stages of COPD)
Symptoms of Lung Cancer:
- Shortness of breath
- Difficulty breathing
- Persistent cough (dry or wet)
- Coughing up blood (or blood-streaked mucus)
- Chest pain
- Hoarse voice
- Recurring lung infections
- Chronic weakness or fatigue
- Loss of appetite
- Unexplained weight loss
Now, while some of these symptoms seem very similar, they can present themselves very differently in people with lung cancer versus people with COPD. Also, it's important to remember that every case of lung cancer and COPD is different, and symptoms can vary widely between people with the same disease.
One major difference between lung cancer and COPD symptoms is that COPD symptoms are life-long and don't get much better with treatment or time. They often start out very mild in the early stages of COPD and slowly get worse over the course of months and years.
Lung cancer symptoms, on the other hand, can get better with successful treatment and even fully disappear if the cancer is cured. However, symptoms often don't show up until the later stages of cancer, when the cancer is much less treatable and has likely already spread.
People who are diagnosed with early-stage COPD can live with the disease for many years before the symptoms get severe enough to significantly burden their lives. People with moderate to severe lung cancer symptoms are not likely to live long with the disease unless their cancer can be successfully treated or cured.
Certain Types of Lung Cancer are More Strongly Associated with COPD
There are at least a dozen different kinds of lung cancer, but the most common ones fall into one of two main types: small cell lung cancer (SCLC) or non-small cell lung cancer (NSCLC). Non-small cell lung cancers are by far the most common, and they make up about 80-85 percent of all lung cancers.
Compared to non-small cell lung cancers, small-cell lung cancers tend to be more aggressive and progress more quickly. However, every case of lung cancer is different, and how the disease presents and progresses can vary significantly from person to person.
All types of lung cancer are strongly associated with both smoking and COPD. About 85 percent of all lung cancers are caused by smoking, and about 40-70 percent of people with lung cancer also have COPD.
However, some types of lung cancer are more closely tied to smoking and COPD than others. People with COPD seem to be more prone to non-small cell lung cancers and have a particularly high risk for squamous cell carcinoma (a sub-type of NSCLC).
In fact, about half of all people who get non-small cell lung cancer also have COPD, and about 80 percent are current or former smokers. Small-cell lung cancers, by comparison, are almost always associated with smoking; up to 98 percent of of SCLC patients have a history of smoking.
Here is a table describing some of the most common types of lung cancers.
Type of Lung Cancer
Small Cell Lung Cancer (SCLC)
Rare: only about 10-15% of lung cancers are small cell lung cancers.
Small cell carcinoma and combined small cell carcinoma
Small cell lung cancers tend to be fast-growing and aggressive.
Non-Small Cell Lung Cancer (NSCLC)
Common: about 80-85% of lung cancers are non-small cell lung cancers.
Adenocarcinoma of the lung (~30% of NSCLC's), squamous cell lung cancer (~30% of NSCLC's), large-cell undifferentiated carcinoma (~10-15% of NSCLC's)
Non-small cell lung cancers are slower-growing and usually have few symptoms (or none at all) until the later stages. However, large-cell undifferentiated carcinoma tends to progress more quickly than other NSCLC types.
Common, though only a small percentage become cancerous
Usually slow-growing if cancerous, though most lung nodules are benign (non-cancerous) and simply need to be monitored for growth or change. To learn more about lung nodules, check out our guide on the topic.
Other Lung Cancers
Adenosquamous carcinoma of the lung (a small-cell lung cancer), large cell neuroendocrine carcinoma (a non-small cell lung cancer), salivary gland-type lung carcinoma, lung carcinoids, mesothelioma, sarcomatoid carcinoma of the lung (extremely rare), malignant granular cell lung tumor (extremely rare)
Varies depending on type
It's important to note that lung cancer doesn't always stay just in the lungs. Over time, lung cancer can become metastatic, which means that the cancer cells can break off and travel to other parts of the body.
This allows the cancer to take root in other organs, most commonly the bones, brain, liver, adrenal gland, and the other lung. When this happens, the resulting cancer is known as a secondary cancer, and it retains the same characteristics as the cancer it originally came from.
Why Do People With COPD Have a Higher Risk for Lung Cancer?
Now that you know the basics of how both lung cancer and COPD work, let's take a closer look at why one disease affects the other and how both of these diseases are so closely intertwined. We'll look at 3 main factors in particular that help explain the link: shared disease risk factors, accumulated lung damage, and individual susceptibility to lung disease.
Shared Risk Factors
One of the main links between COPD and lung cancer is that both diseases have many of the same risk factors and causes. A risk factor is essentially any kind of health problem, physical characteristic, behavior, or lifestyle factor that is known to increase your risk for developing a certain disease.
This means that some of the things that increase your chances of developing COPD—like tobacco smoke and certain respiratory toxins—can also increase your risk of developing lung cancer. In fact, up to 90% of both COPD cases and lung cancer cases are caused by smoking.
This makes sense if you consider the fact that COPD, just like lung cancer, is associated with repeated damage and inflammation in the lungs. Even if you're not a smoker, being diagnosed with COPD means that you are more likely than people who don't have COPD to have other risk factors that increase your chances of getting lung cancer in the future.
Risk Factors for Lung Cancer:
- Older age
- Smoking tobacco (responsible for about 80% of lung cancer deaths)
- Exposure to secondhand smoke (responsible for up to 7 thousand deaths per year)
- Exposure to radon gas (the second most common cause of lung cancer)
- Exposure to asbestos (especially in an occupational environment)
- Exposure to other carcinogens at work (e.g. diesel exhaust fumes, coal compounds, silica dust, arsenic, etc.)
- Exposure to air pollution
- Previous radiation therapy
- Family history of lung cancer
Risk Factors for COPD:
- Older age
- Smoking tobacco (the number one cause of COPD)
- Exposure to secondhand smoke
- Exposure to radon gas
- Exposure to asbestos
- Exposure to other respiratory irritants, including hazardous fumes, chemicals, and airborne particles, especially in an occupational environment (e.g. dust, car exhaust, and fumes from products like cleaning solutions, adhesives, treated lumber, etc.)
- Exposure to air pollution
- A history of frequent or severe respiratory infections (especially during childhood)
- Alpha-1 Antitrypsin Deficiency (a rare genetic disease)
Lung Damage Caused by COPD
While common risk factors (like genetics) and common causes (like smoking) explain some of the relationship between lung cancer and COPD, there are other factors at play. Research shows that simply having COPD is an independent risk factor for lung cancer on its own.
Researchers also believe that certain types of lung cancer—squamous cell carcinoma, in particular—are the result of COPD-related inflammation in the lungs. After all, chronic inflammation is a well-known cause of cancer as well as an inherent characteristic of COPD
This chronic inflammation causes certain physiological changes to lung tissues, including a decrease in DNA repair proteins and an increase in oxidative stress. These changes—along with the repeated cycles of inflammation, damage, and repair—can lead to cancerous mutations.<