Lung Adenocarcinoma

Lung adenocarcinoma is the most common form of lung cancer in the United States, affecting thousands of people each year. While this diagnosis can feel overwhelming, advances in treatment are helping more people live longer and better lives than ever before.

Table of contents

• What Is Lung Adenocarcinoma?
• Classification of Lung Cancer
• How Common Is This Cancer?
• Where Does It Develop?
• Who Is at Risk?
• Signs and Symptoms
• How Is It Diagnosed?
• Treatment Approaches
• What to Expect

What Is Lung Adenocarcinoma?

Adenocarcinoma is a type of cancer that forms in glandular cells, which are cells in our body that release substances like mucus. When this cancer develops in the lungs, it is called lung adenocarcinoma^[1].

Lung adenocarcinoma begins in glandular cells located on the outer part of the lungs. These cells normally line the tiny air sacs called alveoli, which are the small structures in your lungs where oxygen passes into your bloodstream^[1][4].

This type of lung cancer usually evolves from the mucosal glands. In many cases, it may be found in scars or areas of chronic inflammation in the lungs^[2].

Classification of Lung Cancer

Lung cancers are generally grouped into two main types: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). These names refer to how the cancer cells look under a microscope. Non-small cell lung cancer is much more common, making up 80% to 85% of all lung cancers^[4].

Lung adenocarcinoma is a subtype of non-small cell lung cancer. Within NSCLC, there are three main subtypes: adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Of these three types, adenocarcinomas are the most common^[1].

How Common Is This Cancer?

Lung adenocarcinoma is the most common form of lung cancer in the United States. It represents about 40% of all lung cancers^[1][2]. This means that if 100 people are diagnosed with lung cancer, approximately 40 of them will have adenocarcinoma.

While lung cancer cases and deaths have declined since the 1980s, it remains the leading cause of cancer death in the United States^[2]. In 2015, there were 221,200 new cases of lung and bronchial cancers and more than 158,000 lung cancer deaths^[2].

The mean age of diagnosis of lung adenocarcinoma is 71 years, and this particular cancer is very rare before the age of 20. Over the past four decades, there has been a marked increase in lung adenocarcinoma in women, which has been linked to smoking. In the last two decades, adenocarcinoma has replaced squamous cell cancer of the lung as the most prevalent non-small cell cancer^[2].

Where Does It Develop?

Unlike some other types of lung cancer, adenocarcinoma is more likely to be found on the outer parts of the lungs, in areas called the lung periphery^[2]. Because of this location and because it tends to grow more slowly than other lung cancers, adenocarcinoma is more likely to be found before it has spread to other parts of the body^[1].

Who Is at Risk?

Smoking

Smoking tobacco is still the number one risk factor for lung adenocarcinoma. The disease occurs mainly in current or former smokers. Due to numerous harmful substances called carcinogens present in tobacco smoke, exposure to tobacco increases your risk. The amount of risk is related to how much you have smoked and for how long^[1][2].

However, it is possible to develop lung adenocarcinoma even if you have never smoked. In fact, adenocarcinoma of the lung is the most common type of lung cancer among people who have never smoked. It is the most common subtype to be diagnosed in people who have never smoked^[1][2].

Gender

While not widely known, lung cancer kills more women each year in the United States than even breast cancer. It is the leading cancer killer among women. Lung adenocarcinoma is the most common type of lung cancer in women^[1].

Other Risk Factors

Other risk factors include a family history of lung cancer, or occupational exposure to certain harmful substances such as silica, asbestos, radon, heavy metals, and diesel fumes. However, these are less common than smoking as risk factors^[2].

Signs and Symptoms

The majority of patients who are diagnosed with lung cancer usually present with locally advanced or metastatic disease (cancer that has spread). Only about one third of patients have stage I disease when diagnosed^[6].

Lung cancer typically doesn’t cause symptoms early on. Symptoms of lung cancer usually happen when the disease is advanced. The symptoms that patients experience usually reflect how far the cancer has spread^[6][7].

The most common signs of lung cancer, in order of highest frequency, include^[6][7]:

• A new cough that doesn’t go away or gets worse
• Weight loss
• Dyspnea, which means shortness of breath or difficulty breathing
• Chest pain, which may be worse with deep breathing, coughing, or laughing
• Hemoptysis, which means coughing up blood or rust-colored phlegm
• Bone pain
• Clubbing, a change in the shape of fingers
• Fever
• Generally feeling tired or weak
• Hoarseness
• New onset of wheezing without a history of asthma

Patients with recurring or unresolved lung infections such as bronchitis and pneumonia that are unresponsive to antibiotics should also be further evaluated for lung cancer^[6].

How Is It Diagnosed?

Lung cancer diagnosis often starts with an imaging test to look at the lungs. If you have symptoms that worry you, a healthcare professional might start with an X-ray^[11].

If your healthcare professional thinks you may have lung cancer, a number of tests can be used to look for cancerous cells. Tests may include^[11]:

• Imaging tests: These make pictures of the body and can show the location and size of the lung cancer. Tests might include X-ray, MRI, CT (computed tomography), and positron emission tomography (PET scan)
• Sputum cytology: Sputum is the mucus that is coughed up from the lungs. If you are coughing up sputum, it can be looked at under a microscope and can sometimes show lung cancer cells
• Biopsy: A biopsy is a procedure to remove a sample of tissue for testing in a lab. This is the definitive way to confirm a diagnosis

Once a lesion or tumor is identified with various imaging methods, a biopsy is required to confirm the diagnosis^[6].

Treatment Approaches

Treatment of lung adenocarcinoma is based upon the specific subtype and the extent of spread from the primary tumor. Several different approaches are used, either alone or in combination^[6].

Surgery

Surgical removal of the tumor may be an option, particularly when the cancer has not spread beyond the lungs.

Chemotherapy

Chemotherapy uses drugs to kill cancer cells or stop them from growing. It may be used before surgery to shrink tumors, after surgery to kill any remaining cancer cells, or as the main treatment when surgery is not possible.

Radiation Therapy

Radiation therapy uses high-energy rays to kill cancer cells. It can be used alone or in combination with other treatments.

Targeted Therapy

Targeted therapies are drugs that attack specific characteristics of cancer cells. These treatments may work better when paired with healthy habits like good nutrition and regular exercise^[6].

Immunotherapy

Immunotherapy helps your own immune system fight the cancer. This is one of the newer treatment approaches that has shown promise in lung cancer treatment^[6].

What to Expect

Despite new treatments, the 5-year survival is less than 12% to 15% overall^[2]. However, it’s important to know that many people have been diagnosed with lung adenocarcinoma and are living with this disease. More people are living with lung cancer than ever before, thanks to advances in treatment^[1].

Because adenocarcinoma tends to grow more slowly and is more likely to be found before it has spread, it may have a better outlook than some other types of lung cancer when caught early^[1].

Treatment options are constantly changing, and new therapies are being developed and tested every day. You should rely on your medical team for direct treatment recommendations based on your specific situation^[1].