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What Is Lung Cancer?

The lungs are two spongy organs in the chest that take in oxygen on an inhale and expel carbon dioxide on an exhale. Air enters through the mouth, nose, and trachea then divides into tubes called bronchi. Like the roots of a tree, the bronchi split off into smaller branches called bronchioles, and at the end of the bronchioles are tiny air sacs called alveoli that absorb oxygen into the bloodstream on inhale and remove carbon dioxide on exhale. The right lung is made up of three lobes and the left lung is made of two lobes to make more room for the heart. Lung cancer most commonly starts in the cells lining the bronchi, bronchioles, and alveoli.

According to the American Cancer Society, in the United States, more than 235,700 new cases of lung cancer are diagnosed and there are an estimated 131,800 deaths from the disease each year. Lung cancer is most commonly diagnosed among those 65 or older, with a very small amount of people diagnosed younger than 45. Lung cancer is the leading cause of cancer death among men and women, making up almost 25% of all cancer deaths. 

The chance a man will develop lung cancer is about one in 15, and for women, the risk is about one in 17. Black men are 15% more likely to develop cancer than white men, but the rate of lung cancer in Black women is 14% lower than in white women. 

In Colorado, there are an estimated 2,570 new cases and 1,290 deaths from lung and bronchus cancer each year.

Why Come to CU Cancer Center for Lung Cancer 

The CU Cancer Center is home to one of the world’s best known lung cancer teams. The team has led many different breakthroughs in how to treat cancers that affect the lungs — both for non-small cell lung cancer and small cell lung cancer and other rare cancers of the chest, such as mesothelioma or thymic cancer. The CU Cancer Center is one of four National Cancer Institute-Designated Comprehensive Cancer Centers in the Rocky Mountain region. Our doctors provide top-notch, multidisciplinary, patient-centered care, and we offer treatment options not available at most other medical centers in the country. Importantly, our team specializes in thoracic cancers, allowing us to keep at the very cutting edge of research and the best possible treatment decisions for our patients.

Our doctors are the only physicians in a 500-mile radius who are part of the National Comprehensive Cancer Network (NCCN) advisory panel. The NCCN establishes treatment guidelines that doctors all across the United States use as a reference. 

There are over 160 lung cancer clinical trials, currently being offered by CU Cancer Center members, giving patients many different treatment options. 

The Lung Multidisciplinary Clinic at the CU Cancer Center brings together a team of expert thoracic surgeons, medical oncologists, pathologists, radiologists, and more to focus on problems affecting the lungs. Together, the team analyzes a patient’s diagnosis and recommends a specific treatment plan for the individual by the end of the visit. All of our providers subspecialize in cancers of the lung and chest, utilizing the newest research and treatments of lung and related cancers.


Our clinical partnership with UCHealth has produced survival rates higher than the state average for all stages of lung cancer.

Lung Cancer Graph

Number of Patients Diagnosed – UCHealth 1,800 – State of Colorado 8,046
Number of Patients Surviving – UCHealth 436 – State of Colorado 1,505
*n<30, 5 Year Survival – (Date of diagnosis 1/1/2010–12/31/2014)

Types of Lung Cancer

There are two broad types of lung cancers, non-small cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). About 13% of all lung cancers are small-cell lung cancer and 84% are non-small cell lung cancer.

The most common subtypes of non-small cell lung cancer include:

Adenocarcinomas start in the cells that secrete mucus. They occur mainly in current or former smokers but are the most common type in non-smokers. Adenocarcinomas are more common in women than in men and are more commonly diagnosed in younger people than other types of lung cancers. 

Squamous cell carcinomas start in the squamous cells, flat cells that line the inside of the bronchi and bronchioles. Squamous cell carcinomas are often linked to smoking and are often found near the bronchus.

Large cell carcinomas appear in any part of the lung and grow and spread quickly, making them difficult to treat. 

Small-cell lung cancer grows and spreads faster than non-small cell lung cancer. About 70% of people with small-cell lung cancer are diagnosed with cancer that has already spread. This type of lung cancer responds well to chemotherapy and radiation but is reoccurring in most cases. 

Causes of Lung Cancer

Smoking tobacco is a predominant cause of most lung cancers. Importantly, not all people who get lung cancer are smokers or are exposed to secondhand smoke. Exposure to radon, air pollution, asbestos, and diesel exhaust, among other chemicals, can cause lung cancers in non-smokers. 

Non-smoker lung cancers tend to be different from cancers that occur in smokers. They occur more commonly in younger people and have gene changes that are different from tumors found in smokers. 

→ Hear from two non-smoking lung cancer patients

DNA changes or mutations that occur within healthy lung cells can lead to abnormal growth and cancer. Cells contain DNA that tells the cell what to do. When a cell’s DNA is damaged, cells continue to grow and divide where they aren’t needed by the body. This buildup of cells becomes a tumor. 

Risk Factors for Lung Cancer

There are several factors that might increase the chance of developing lung cancer. These risk factors include: 

Smoking: By far the leading risk factor for lung cancer, smoking accounts for upward of 80% of lung cancer deaths. Small-cell lung cancer is very rarely diagnosed in people who have never smoked.

Secondhand smoke: It is believed that more than 7,000 deaths from lung cancer are caused by secondhand smoke each year. 

Radon: This naturally occurring radioactive gas is a result of uranium breaking down in soil and rocks. It is odorless and tasteless and the second leading cause of lung cancer in the United States. It is the leading cause among non-smokers.

Asbestos: This naturally occurring mineral is commonly used in mines, mills, textile plants, and shipyards. People who work with asbestos are more likely to die from lung cancer.  

Previous radiation: People who receive radiation therapy on or near their chest for other cancers have a higher risk for lung cancer. This does not include women who have radiation therapy to the breast.

Latest in Lung Cancer from the CU Cancer Center

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Information reviewed by D. Ross Camidge, MD, PhD, February 2021.