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 lymphatic system and the bloodstream, leading to metastasis.
The three main types of NSCLC are based on the types of cells that form the tumor:
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).
What are the risk factors?
Factors that may increase the risk for lung cancer include:
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.
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 50 to 80 who have smoked a pack of cigarettes every day for at least 20 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 sampling 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. At the same time, endobrachial ultrasound (EBUS) uses a small ultrasound within the airway to examine the lymph nodes for staging.
Surgical diagnosis and staging involve performing 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 to identify abnormal proteins or biochemical processes in the cancer cells. Targeted therapy can be used against abnormal proteins or biochemical processes, while immunotherapy uses your body's immune system to treat tumors.
How is NSCLC staged?
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 4:
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 lining of the airway.
Stage 1—The cancer hasn’t spread to any lymph nodes and the tumor is 4 centimeters or less in size.
Stage 2—The cancer has grown in size or spread to lymph nodes within the same side of the chest.
Stage 3—The cancer has grown or spread to lymph nodes within the middle of the chest, is larger than 7 centimeters in size, or has invaded adjacent structures. It may not be possible to remove it with surgery.
Stage 4—The cancer has spread throughout the lungs or to distant parts of the body and may not be removed with surgery.
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 1—Surgery may be the only treatment needed, but chemotherapy may be recommended post-surgery if the cancer has a high risk of recurring.
Stage 2—Surgery may be done to remove a whole lobe of lung or a portion of the 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 3—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 genetic mutations, doctors may recommend immunotherapy, which uses the body’s immune system to fight cancer.
Stage 4—Treatment usually starts with systemic therapy, a combination of chemotherapies and/or immunotherapies. Because these cancers are not curable, doctors may try all the types of treatment options and make adjustments depending on the patient's response to best control the disease.
Survival rate
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. If the cancer is small, peripheral in location, and has not spread to lymph nodes or any adjacent structures, the five-year survival can be greater than 90 percent.
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.
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