For Malignant Mesothelioma
Determining the presence of malignant pleural mesothelioma and the type of mesothelioma requires examination of tissues removed from the lung. Tissue examination confirms the diagnosis and can be evaluated for biomarkers that may help direct treatment with precision cancer medicines. Sometimes this can be accomplished by looking for cancer cells in the sputum or by the removal of fluid from a pleural effusion (thoracentesis) for evaluation under a microscope. More commonly however, a biopsy which is the removal of a small piece of tissue for examination under a microscope is required. While there was once a concern that needle biopsy could spread the cancer, research indicates that a needle biopsy of the pleura is a safe procedure and it detects malignant mesothelioma approximately 86% of the time.1 A biopsy can be obtained using one or more of the following procedures.
CT Guided Fine Needle Aspiration Biopsy: CT guided fine needle aspiration biopsy is the most common way to evaluate possible cancers. A CT scan takes a very detailed picture of a patient’s suspected cancer, allowing the insertion of a thin needle to remove a sample of the tissue. This gives doctors the most information without resorting to a more invasive surgery (thoracotomy) and direct biopsy.
Thoracotomy: During a thoracotomy, a surgeon makes a large incision in a patient’s chest in order to directly access the mass and directly remove part or all of the suspicious area. In some patients with a peripheral lung mass and no evidence of mediastinal or systemic cancer, a wedge resection of the lesion is sometimes performed and diagnosis made on a frozen-section of tissue. If lung cancer is confirmed, a formal cancer resection is then performed.
Endoscopic Ultrasound Guided Fine Needle Aspiration Biopsy: The mediastinum is the area behind the breast bone and consists of blood vessels, lymph nodes and other structures. Because lung cancer frequently spreads to lymph nodes in the mediastinum, biopsies to this area are often necessary. An endoscopic ultrasound guided fine needle aspiration biopsy is often used to evaluate the mediastinum. This technique is performed in order to avoid the more invasive procedures of mediastinoscopy or thoracotomy. Using this technique, more invasive methods of diagnosis can be avoided in approximately 50% of patients. An ultrasound machine is used to take pictures of the mediastinum, allowing a small biopsy needle to be directly inserted into the suspicious area without making an incision in the chest.
Cervical Mediastinoscopy: Mediastinoscopy is another diagnostic procedure used to determine whether mediastinal lymph nodes contain cancer. This procedure is used in cases where endoscopic ultrasound guided fine needle aspiration biopsy is not indicated or was not successful. Medianstinoscopy requires general anesthesia, a small anterior neck incision and insertion of an endoscope, which is a thin, lighted tube. A complete procedure includes extensive sampling of lymph nodes in the upper and lower mediastinum.
Bronchoscopy: During a bronchoscopy, a physician 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.
Thorascopy: During this procedure, an endoscope called a thorascope is inserted through a small incision in the chest wall. Thorascopy is a limited surgical procedure that allows the lining of the chest wall and the lungs to be examined and biopsied to determine if cancer is present.
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.
Thoracentesis: During a thoracentesis, a needle is inserted through the chest wall into the pleural space in order to remove a sample of the fluid that surrounds the lungs in order to check for the presence of cancer cells.
Following a tissue diagnosis of mesothelioma, it is important to accurately determine the stage of cancer in order to begin treatment planning.
The stage describes how far the cancer has spread and each stage of cancer may be treated differently. There are many staging systems, but TNM is the most common. “T” refers to the size of the tumor, “N” to the number of lymph nodes involved, and “M” to metastasis. TNM staging measures the extent of the disease by evaluating these three aspects and assigning a stage, which is usually between 0-4. Generally, the lower the stage, the better the treatment prognosis (outcome) is.
A new international staging system for malignant pleural mesothelioma that is TNM-based was created in June 1994 at the Seventh World Conference of the International Association for the Study of Lung Cancer.2 There are currently six stages of malignant pleural mesothelioma: IA, IB, II, III, IV and Occult. While a higher stage number generally correlates with a worse prognosis, this system is relatively new and outcomes cannot be predicted with certainty. Determining mesothelioma stage requires obtaining a sample of lung and lymph nodes, which is typically performed during thoracentesis, and evaluating them under a microscope.
Once cancer has been diagnosed, a careful evaluation will be made to determine how far the cancer has spread (also called stage). In order to begin evaluating and discussing treatment options with their healthcare team, patients need to know the correct stage of their cancer. The following tests may be performed to accurately stage mesothelioma:
Chest x-ray: A chest radiograph may show pleural effusions or pleural thickening.
Computed tomography (CT): A CT scan may show whether there is fluid, thickening, or irregularities in the pleural. CT may also be helpful for determining whether the cancer has spread beyond the pleura into the chest wall, pericardium (sack around the heart), diaphragm (breathing muscle), or the lymph nodes.
Magnetic resonance imaging (MRI): An MRI scan can be particularly useful to determine how extensive the cancer is and whether it can be removed with surgery. In addition to identifying the extent and whether the cancer can be removed with surgery, a special type of MRI, called contrast-enhanced MRI, is also helpful for differentiating mesothelioma from other types of cancer.3
Positron emission tomography (PET): Unlike techniques that provide anatomical images, such as X-ray, CT and MRI, PET shows chemical and physiological changes related to metabolism. This is important because these functional changes often occur before structural changes in tissues. PET images may therefore show abnormalities long before they would be revealed by X-ray, CT, or MRI. PET can sometimes distinguish between malignant and non-malignant fibrous processes in the pleura.3
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.
Patients with stage I-III disease have cancer that can potentially be removed with surgery.
Stage IA: Patients with stage IA disease have cancer limited to the pleura on one side of the chest with no involvement of lymph nodes and no spread to other sites.
Stage IB: Patients with stage IB disease have cancer that has spread to the parietal pleura, including mediastinal and diaphragmatic pleura on one side of the chest and can have scattered foci of tumor also involving the visceral pleura. There is no involvement of lymph nodes or distant spread.
Stage II: Patients with stage II disease have cancer involving both parietal and visceral pleura and can have involvement of diaphragmatic muscle or extension into the lung. There can be lymph node involvement, but there is no distant spread.
Stage III: Patients with stage III cancer have locally advanced but potentially surgically resectable cancer. They have cancer involving parietal, mediastinal, diaphragmatic, and visceral pleura. They can also have spread to fascia, mediastinal fat, and soft tissue of the chest wall or involvement of the pericardium. These patients can have spread to the bronchopulmonary or hilar lymph nodes or to subcarinal or mediastinal lymph nodes, including the internal mammary nodes. They do not have spread to the opposite side of the chest or distant metastasis.
Patients with stage IV disease have cancer that cannot be typically removed with surgery. They have spread of cancer to the mediastinal, internal mammary or supraclavicular lymph nodes on the side of the chest opposite to the original cancer. Distant metastasis can also be present.
Patients with recurrent cancer have disease recurrence after primary treatment or failed primary treatment.
1 Adams RF, Gray W, Davies RJ, et al. Percutaneous image-guided cutting needle biopsy of the pleura in the diagnosis of malignant mesothelioma. Chest. 2001;120:1798-802.
2 Rusch VW. A Proposed New International TNM Staging System for Malignant Pleural Mesothelioma. Chest 1995;108:1122-1128.
3 Eibel R, Tuengerthal S, Schoenberg SO. The Role of New Imaging Techniques in Diagnosis and Staging of Pleural Mesothelioma. Current Opinion in Oncology. 2003;15:131-138.