Lung Adenocarcinoma

Lung adenocarcinoma is the most common form of lung cancer. It can develop in anyone, including people who have never smoked.

Lung adenocarcinoma is the most common form of lung cancer in people who have never smoked. It differs from most other lung cancers because many adenocarcinomas have identified genetic biomarkers that can direct treatment.
It can be hard to diagnose in early stages because it often causes no symptoms early in the disease.
Treatments may include surgery, radiation and chemotherapy, immunotherapy and targeted drug therapies for tumors with known biomarkers.

What is lung adenocarcinoma?

Lung adenocarcinoma is a type of lung cancer that develops from cells that line the airways and help produce certain substances such as mucus. It is the most common type of lung cancer and the most common type of non-small cell lung cancer. It can affect adults of any sex and age, but is diagnosed most often in older adults.

The name adenocarcinoma describes the type of cell the cancer starts in and the way it behaves:

“Adeno” means glandular — a type of cell found in the lungs and other parts of the body that produce and release substances such as mucus. Glandular cells are a type of an epithelial cell, the cell that lines organs, body surfaces and internal passageways.
“Carcinoma” refers to cancer that begins in epithelial cells. Lung adenocarcinoma develops when genetic changes cause the glandular epithelial cells in the lung to start growing and dividing uncontrollably, forming a tumor. A carcinoma is a malignant tumor, meaning it can invade nearby tissues and spread (metastasize) to other parts of the body.

Where in the lungs can adenocarcinoma develop?

Adenocarcinomas can develop in any area of the lung. However, unlike some other lung cancers that often develop in the larger central airways, adenocarcinomas are more likely to form in the outer regions of the lungs, including the tiny air sacs where oxygen enters the bloodstream.

Because these tumors can grow for some time before affecting major airways, symptoms may not appear until the cancer becomes larger or more advanced.

What causes lung adenocarcinoma?

Lung adenocarcinoma develops when cells in the lung undergo genetic changes that disrupt their normal growth and cause a tumor to form. Scientists do not fully understand why these genetic changes occur. In some people, they appear to result from exposure to substances that damage DNA, such as tobacco smoke. In others, the changes may occur without a clear cause.

Researchers identified some of the genes that can lead to adenocarcinoma growth if the gene changes (mutates). These genes include EGFR, KRAS, ALK, MET, HER2, RET, NTRK, ROS1 and BRAF. Testing for these genetic changes is important and can help inform treatment, including drug therapies that target specific biomarkers.

Is lung adenocarcinoma inherited?

Most people with lung adenocarcinoma do not inherit the gene changes (mutations) from a parent. The genetic changes that lead to this type of cancer usually develop over a person’s lifetime. However, researchers think genetics may play a role in increasing the risk of developing lung adenocarcinoma in some families.

Can nonsmokers have lung adenocarcinoma?

Yes, nonsmokers can develop lung adenocarcinoma. Although smoking is a major cause of lung cancer, lung adenocarcinoma is the most common type of lung cancer diagnosed among people who have never smoked.

Researchers are studying why this happens. Possible risk factors include:

Secondhand smoke exposure.
Radon exposure.
Air pollution.
Occupational exposures: People who work around substances known to increase lung cancer risk, such as asbestos, diesel exhaust, silica dust and certain industrial chemicals, may have a higher risk of developing lung adenocarcinoma.
Inherited risk factors.
Previous chest radiation.

In many cases, no specific cause can be identified.

Can lung adenocarcinoma be prevented?

While there is no guaranteed way to prevent lung adenocarcinoma, certain steps may help reduce risk:

Reduce or quit smoking.
Avoid secondhand smoke.
Test your home for radon.
Follow workplace safety guidelines around hazardous substances.
Reduce exposure to air pollution when possible.

Symptoms of Lung Adenocarcinoma

Because lung adenocarcinoma often develops in the outer portions of the lungs rather than the main airways, it may not cause symptoms until the tumor grows larger or spreads. Some people with early-stage lung adenocarcinoma have no symptoms at all. The cancer may be discovered incidentally during imaging performed for another reason.

When symptoms do occur, they may include the following:

A cough that does not go away or gets worse over time
Shortness of breath
Chest pain or discomfort
Wheezing
Coughing up blood or blood-streaked mucus
Hoarseness
Frequent or persistent respiratory infections, such as pneumonia or bronchitis
Fatigue
Unexplained weight loss
Loss of appetite

Because these symptoms are shared with many other lung conditions, having one or more of them does not necessarily mean a person has lung cancer.

In advanced stages, lung adenocarcinoma may spread beyond the lungs to other parts of the body, which can cause additional symptoms. They vary depending on where the cancer has spread, which commonly includes these areas of the body:

Bones
Brain
Liver
Adrenal glands
Lymph nodes

Any new or persistent symptoms should be checked by a doctor. Early evaluation may help find the cause of symptoms and, if cancer is present, increase the likelihood of finding it at an earlier stage, when treatment may be more effective.

How is lung adenocarcinoma diagnosed?

Diagnosing lung adenocarcinoma typically involves a combination of physical exam, imaging tests, tissue sampling (biopsy) and laboratory testing.

Medical history: Your doctor will review your symptoms, medical history and risk factors for lung cancer.
Physical exam: The exam may include listening to your lungs with a stethoscope, checking your breathing and examining lymph nodes, skin and other areas of the body for potential signs of cancer.
Imaging tests: Imaging studies can help detect a lung tumor, determine its size and location, and look for evidence that cancer has spread. Common imaging tests include:
- Chest X-ray: May identify an abnormal spot or mass in the lung.
- Computed tomography (CT) scan: Provides more detailed images of the lungs.
- Positron emission tomography (PET) scan: Helps determine whether cancer may have spread to lymph nodes or other organs. Doctors often evaluate nearby lymph nodes because they are one of the first places lung cancer may spread.
- Magnetic resonance imaging (MRI): May be used to see if the cancer spread to the brain or other structures.
Biopsy: While imaging tests can identify a growth, they cannot definitively diagnose lung adenocarcinoma. A biopsy is usually needed to confirm which cells the tumor is made of and whether it’s malignant. Biopsies involve collecting a sample of tissue from the tumor so it can be examined under a microscope by a pathologist.

Biomarker Testing

If lung adenocarcinoma is diagnosed, additional testing is often performed on the tumor tissue to look for specific genetic alterations, sometimes called biomarkers or driver mutations.

Examples include alterations involving genes such as EGFR, ALK, MET, HER2, RET, NTRK, KRAS, ROS1 and BRAF.

Tumors may also be tested for proteins such as PD-L1. The results can help identify targeted therapies or immunotherapies that may be effective treatment options.

Staging Lung Adenocarcinoma

Additional testing may be performed to determine the stage of the cancer. Staging considers the size of the tumor, whether cancer has spread and how far it has spread.

Knowing the stage helps doctors develop a tailored treatment plan and estimate prognosis. Lung adenocarcinoma stages include:

Stage 0: Abnormal cells are found in the lining of the air sacs and have not invaded surrounding tissue.
Stage I: Cancer is found only in the lung.
Stage II: Cancer has spread within the lung or to nearby lymph nodes.
Stage III: Cancer has spread to lymph nodes or structures within the chest.
Stage IV: Cancer has spread to distant organs, such as the bones, brain, liver or adrenal glands.

Can lung adenocarcinoma be detected early?

Some cases of lung adenocarcinoma can be detected before symptoms develop through lung cancer screening. Screening is recommended only for people at increased risk of lung cancer based on age and smoking history. Current guidelines recommend annual low-dose computed tomography (LDCT) screening for adults who meet all the following criteria:

Are 50 to 80 years old
Have a smoking history of at least 20 pack-years (for example, smoking one pack per day for 20 years or two packs per day for 10 years)
Currently smoke, or quit within the past 15 years

Is there screening for people who have never smoked?

At this time, routine lung cancer screening is not generally recommended for people without a significant smoking history, even though lung adenocarcinoma can occur in nonsmokers.

Researchers continue to study whether additional groups may benefit from screening, including people with other risk factors such as family history or radon exposure.

How Is lung adenocarcinoma treated?

Treatment for lung adenocarcinoma depends on several factors, including the cancer stage, the presence of specific biomarkers and the person’s overall health. Treatment goals are unique to each patient and stage, and may include eliminating the cancer, controlling its growth, easing symptoms and improving quality of life.

Treatment may involve one approach or a combination of therapies, including:

Surgery: Surgery is often the preferred treatment for early-stage lung adenocarcinoma that has not spread beyond the lung. Depending on the size and location of the tumor, a surgeon may remove a portion of the lung or the entire lung. Nearby lymph nodes may also be removed and examined for signs of cancer spread.
Radiation therapy: Radiation therapy uses high-energy beams to destroy cancer cells. It can be used after surgery to reduce the risk of cancer coming back. It can also be the main treatment when surgery is not an option, such as if the tumor is near major blood vessels.
Chemotherapy: Chemotherapy uses medications that destroy or slow the growth of cancer cells throughout the body. It can be used to shrink the tumor before surgery or to destroy remaining cancer cells after surgery. It can also be the main treatment for advanced or metastatic lung adenocarcinoma that cannot be removed with surgery.
Targeted drug therapy: Targeted therapy uses medications (usually taken by mouth or infusion) that block specific genetic alterations or proteins that help cancer cells grow and spread. If biomarker testing identifies one of these alterations, targeted therapy may be an option.
Immunotherapy: Immunotherapy can help the body’s immune system recognize and attack cancer cells. Some immunotherapies work by blocking proteins that cancer cells use to avoid detection by the immune system. Testing for biomarkers such as PD-L1 may help determine whether immunotherapy is likely to be beneficial.

Treatment for Advanced or Metastatic Lung Adenocarcinoma

When lung adenocarcinoma has spread beyond the lung, treatment typically focuses on controlling the disease, prolonging survival and maintaining quality of life. Surgery is often not an option, but the other treatment approaches can still be used.

Because treatment recommendations vary widely based on the tumor’s biomarker profile and stage, people with advanced lung adenocarcinoma often receive individualized treatment plans.

Clinical Trials

Clinical trials evaluate new approaches to diagnosing and treating lung adenocarcinoma. Participation in a clinical trial may offer access to emerging therapies and can be an option at various stages of treatment.