Non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, according to the American Society of Clinical Oncology (ASCO). It makes up 84 percent of lung cancers.

NSCLC occurs when cells in the lungs change and grow out of control. It starts in the epithelial cells, which are found in the inner linings of the lungs. As cancer cells grow, they form a tumor. The tumor may shed cancer cells that spread to other parts of the body via the bloodstream, leading to metastasis.

The three main types of NSCLC are based on the types of cells that form the tumor:

• Squamous cell carcinoma, which begins in the flat cells lining the lung’s airways.
• Adenocarcinoma, which begins in mucus-producing cells of the lung.
• Large cell carcinoma, which begins in several types of large cells found in the lung and doesn’t show signs of either squamous or adenocarcinoma cells (undifferentiated).

Factors that may increase the risk for lung cancer include:

• Tobacco use (including cigarettes and cigars)
• Secondhand tobacco smoke
• Radon
• Workplace exposure to asbestos, arsenic, diesel exhaust, silica and chromium
• Radiation therapy (X-ray treatments of the chest to treat cancer)
• Family history of lung cancer in a parent or sibling

Lung cancer symptoms vary from person to person. Early cancer that hasn’t spread beyond the lung doesn’t usually cause symptoms.

As the cancer grows and spreads, symptoms may occur, which include:

• Coughing that persists or worsens
• Blood in the sputum or mucus
• Wheezing or shortness of breath
• Chest pain
• Fatigue
• Unexplained weight loss

Sometimes the first sign of non-small cell lung cancer is a spot on a routine chest X-ray. As cancer grows and spreads through the lungs or to other areas of the body—such as the lymph nodes, bones, brain or liver—more symptoms may develop.

These may include:

• Difficulty breathing
• Abdominal pain
• Bone pain
• Weakness
• Headaches
• Seizures
• Hoarseness or speech difficulty

Imaging studies typically mark the beginning of the lung diagnostic process. Blood tests aren’t used to diagnose lung cancer.

Important imaging tests include:

• Computed tomography (CT) scans
• Positron emission tomography (PET) scans
• Magnetic resonance imaging (MRI) scans
• Bone scans

In people at high risk, yearly screenings with a low-dose CT scan may help detect the cancer before symptoms start. ASCO recommends yearly screenings for patients aged 55 to 74 who have smoked a pack of cigarettes every day for at least 30 years, even if they have quit in the past 15 years.

Although imaging studies may detect lung cancer, a biopsy is necessary for a final diagnosis. A biopsy, which involves removing lung cancer cells and examining them under a microscope, may be performed in several ways, including:

• Bronchoscopy involves a doctor inserting a flexible scope down the throat into the lungs. Other types of scopes include a mediastinoscopy for chest lymph nodes and a thoracoscopy for deep lung tissue.
• Needle aspiration involves placing a long needle through the chest to remove a sample of lung tumor.
• Thoracentesis collects cancer cells from fluid around the lung.
• Thoracotomy involves a surgeon opening the chest to take a biopsy directly from the lungs.

After a biopsy, patients may undergo additional tests to look for genetic mutations or proteins in the cancer cells. Tumors that have mutations may respond to a type of cancer therapy called targeted therapy, while tumors with certain proteins may respond to a type of therapy called immunotherapy.

The final step in diagnosis, before treatment, is staging. The stage of lung cancer indicates the size of a tumor and whether it has spread, helping to determine the appropriate treatment options.

Stages for NSCLC run from 0 through IV:

• Occult stage, or hidden stage—Sputum or bronchial washings may reveal the presence of cancer cells, but neither imaging nor a bronchoscopy may detect the cancer.
• Stage 0—The cancer hasn’t spread outside the lung.
• Stage I—The cancer hasn’t spread to any lymph nodes.
• Stage II—The cancer has grown in size or spread to lymph nodes.
• Stage III—The cancer has grown or spread to lymph nodes, and it may not be possible to remove it with surgery.
• Stage IV—The cancer has spread throughout the lungs or to distant parts of the body and may not be removed with surgery.

Treatment of NSCLC depends on the stage.

The most likely options include:

• Stage 0—Surgery alone is the usual treatment, without chemotherapy or radiation therapy. In most cases, only a wedge of lung tissue needs to be removed.
• Stage I—Surgery may be the only treatment needed, but chemotherapy may be recommended post-surgery if the cancer has a high risk of recurring.
• Stage II—Surgery may be done to remove a whole lobe of lung or the entire lung. Chemotherapy often follows surgery. If tests of the cancer cells show gene mutations, then targeted drug therapy may be used to attack the tumor cells.
• Stage III—Some combination of chemotherapy and radiation therapy is the likely treatment. Surgery or targeted therapy may also be used. If cancer cells have certain types of proteins, doctors may recommend immunotherapy, which uses the body’s immune system to fight cancer.
• Stage IV—Because these cancers are harder to treat, doctors may try all the types of treatment options and make adjustments depending on the patient’s response.

The five-year survival rate for this type of lung cancer is 25 percent, according to the American Cancer Society. That increases to 63 percent for NSCLC cases where the cancer hadn’t spread outside the lung.

It’s important to remember that the five-year survival rate is only an estimate, not an exact prediction. Since experts measure survival every five years, the numbers may not reflect newer and better diagnosis and treatment options, many of which are the result of clinical trials of new drugs.