Lung cancer is characterized by the uncontrolled growth of abnormal cells in one or both of the lungs. The majority of lung cancers begin in the bronchial tubes that conduct air in and out of the lungs. Cancers of the lung are classified by how they appear under a microscope. While there are more than a dozen different kinds of lung cancer, the two main types of lung cancer are non small cell and small cell, which together account for over 90% of all lung cancers. Non small cell lung cancer accounts for approximately 75% of these cancers and consists of squamous cell, adenocarcinoma and large cell types. Small cell lung cancer represents 20-25% of all lung cancers and is also referred to as “oat cell cancer” because of the shape of cells when examined under the microscope.
When lung cancer is diagnosed, the doctor must determine the type (small cell or non small cell) and the extent of spread or stage of the cancer in order to determine the best treatment. Lung cancer may grow locally in the lungs or spread distantly (metastasize) to other sites in the body, including lymph nodes, bones, and the brain. Determining the presence of a lung cancer and the type of lung cancer requires examination of tissues from the lung. A biopsy is the removal of a small piece of tissue for examination under a microscope and can be obtained using one or more of the following procedures.
Bronchoscopy: During a bronchoscopy, a surgeon inserts a bronchoscope (thin, lighted tube) through the nose or mouth into the trachea (windpipe) and bronchi (air passages that lead to the lung). Through this tube, the surgeon can examine the inside of the trachea, bronchi and lung and collect cells or small tissue samples.
Fine Needle Aspiration: During this procedure, a surgeon inserts a needle through the chest into the cancer to remove a tissue sample for examination under the microscope.
Thoracentesis: During a thoracentesis, a surgeon uses a needle to remove a sample of the fluid that surrounds the lungs in order to check for the presence of cancer cells.
Thoracotomy: A thoracotomy is a major operation, which involves opening the chest in order to diagnose lung cancer.
Sputum Cytology: Sputum cytology is a procedure used to examine mucus that is coughed up from the lungs or breathing tubes. The mucus is examined under a microscope in order to detect cancer cells.
After lung cancer has been confirmed, other tests may be performed on the specimen in order to further classify the cancer and determine the optimal treatment strategy. Based on the stage of the cancer and the results of these tests, treatment of lung cancer is individualized.
Staging: Determining the stage or extent of spread of the cancer is essential in order to understand treatment options or interpret published cancer treatment information. Determining the stage of lung cancer may require many tests, which often include the following:
Mediastinoscopy: A mediastinoscopy is a procedure that can indicate whether the cancer has spread to the lymph nodes in the chest. During a mediastinoscopy, a surgeon inserts a mediastinoscope (lighted tube) through a small incision in the neck while a patient is under general anesthesia. This mediastinoscope allows the surgeon to examine the center of the chest (mediastinum) and nearby lymph nodes, as well as remove a tissue sample.
Computed Topography or CT Scan: A CT scan is a technique for imaging body tissues and organs, during which X-ray transmissions are converted to detailed images, using a computer to synthesize X-ray data. A CT scan is conducted with a large machine positioned outside the body that can rotate to capture detailed images of the organs and tissues inside the body. This method is more sensitive and precise than the chest x-ray.
Magnetic Resonance Imagery or MRI: During MRI, a powerful magnet linked to a computer makes detailed pictures of areas inside the body.
Positron emission tomography (PET): Positron emission tomography (PET) scanning has been used to improve the detection of cancer in lymph nodes. One characteristic of living tissue is the metabolism of sugar. Prior to a PET scan, a substance containing a type of sugar attached to a radioactive isotope (a molecule that spontaneously emits radiation) is injected into the patient’s vein. The cancer cells “take up” the sugar and attached isotope, which emits positively charged, low energy radiation (positrons). The positrons react with electrons in the cancer cells, which creates the production of gamma rays. The gamma rays are then detected by the PET machine, which transforms the information into a picture. If no gamma rays are detected in the scanned area, it is unlikely that the mass in question contains living cancer cells.
Bone Scan: A bone scan is used to determine whether cancer has spread to the bones. Prior to a bone scan, a surgeon injects a small amount of radioactive substance into a vein. This substance travels through the bloodstream and collects in areas of abnormal bone growth. An instrument called a scanner measures the radioactivity levels in these areas and records them on x-ray film.
Testing the tumor for specific characteristics: An important advance in the treatment of several types of cancer is the development of targeted therapies—drugs that target specific biological pathways involved in the growth or spread of cancer. For some of these therapies, it’s possible to test the cancer before treatment in order to determine whether the cancer is likely to respond to treatment. Non-small cell lung cancer, for example, may be tested for changes in certain genes.
EGFR gene: Mutations in the epidermal growth factor receptor (EGFR) gene may affect how non-small cell lung cancer responds to certain drugs. EGFR contributes to the growth of several types of cancer, and drugs that block the activity of EGFR can slow cancer growth. An EGFR-targeted drug that has been shown to benefit selected patients with non-small cell lung cancer is Tarceva® (erlotinib). Tarceva is currently approved for the treatment of advanced non-small cell lung cancer after initial treatment has failed, or as maintenance therapy after chemotherapy. Although Tarceva is not currently approved for the initial treatment of non-small cell lung cancer, studies in newly diagnosed patients suggest that certain mutations in the EGFR gene improve the cancer’s responsiveness to Tarceva.
ALK gene: Up to 7% of non-small cell lung cancers have an abnormal version of the ALK gene that contributes to the growth and development of cancer cells. Xalkori™ (crizotinib) is an oral medication that blocks certain proteins, including the protein produced by this abnormal gene. For advanced non-small cell lung cancers that test positive for the ALK gene abnormality, Xalkori has produced very promising rates of response.
All new treatment information is categorized according to whether patients have small cell or non-small cell lung cancer and according to the stage of disease. To learn more about the general treatment of lung cancer and current results achieved with new treatments, select small cell or non-small cell lung cancer.
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