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A-PDF Watermark DEMO: Purchase from www.A-PDF.com to remove the watermark David C. Rice, MB, BCh Associate Professor of Surgery The University of Texas, M.D. Anderson Cancer Center Staging refers to the process of defining the anatomic extent of a tumor. Based on extent cancers are placed into one of 4 stage groupings which encompass the spectrum from early stage localized tumors (Stage I) to advanced stage tumors that have spread to other organs (Stage IV). The purpose of staging is to define groups of patients who have similar prognosis and to guide appropriate therapy. It is essential that cancers be properly staged prior to embarking on treatment so that the most effective form of therapy can be delivered to the patient. Staging that occurs based on clinical information available prior to surgery is called ‘clinical staging’ and is generally less accurate than ‘pathologic staging’ which is based on precise anatomic information available only after the tumor has been examined after surgery. The most widely accepted staging system for mesothelioma is that endorsed by the International Mesothelioma Interest Group (IMIG) and the American Joint Commission on Cancer (AJCC). This system defines stage according to the extent of the tumor itself, the involvement of lymph glands (or nodes) and the presence of metastases to other organs. The current AJCC staging system is under evaluation and will probably be revised within the next few years. Other staging systems in clinical use include the Brigham and Women’s Staging System and the Butchart Staging System In its earliest manifestation, mesothelioma appears as multiple small white nodules that involve the thin translucent lining of the chest wall (parietal pleura). In general there is diffuse involvement of the pleura rather than a single discrete focus of tumor. This stage is rarely diagnosed and may be seen as either slight thickening of the pleura on CT scans or as fluid accumulation between the chest wall and lung (pleural effusion). As tumor spreads it will involve the thin pleural lining the lung surface (visceral pleura). The radiographic findings are similar to Stage Ia except there may be nodularity of the pleura seen in between the different lobes of the lung. As tumor grows it may invade into the lung or diaphragm (the muscle in between the chest cavity and the abdomen). CT scan is imprecise at accurately predicting either lung or diaphragm invasion, although in general the greater the degree of pleural thickening and tumor bulk, the greater the chance of lung or diaphragm invasion. Mesothelioma may grow across the pleural lining of the chest wall to invade into the substance of the chest wall itself. When this occurs in a single region it denotes Stage III. The tumor frequently invades the chest wall at the site of previous surgical incisions. CT scan and MRI are useful for determining chest wall invasion. Mesothelioma can also invade into the fibrous sac that surrounds the heart (pericardium). When there is only superficial invasion it also denotes Stage III. Lastly, mesothelioma, like other tumors can spread to lymph glands. When it spreads to glands in the chest on the same side as the tumor it denotes Stage III. Radiographic imaging (CT scan, PET scan or MRI) is inaccurate at determining pericardial invasion or nodal involvement. When mesothelioma invades multiple areas of the chest wall, invades through the pericardium or diaphragm, involves lymph glands outside the chest or spreads to other organs it denotes Stage IV disease. Chest wall invasion may be identified with CT or MRI, however they are poor at determining invasion across the diaphragm or pericardium. PET scan is a very useful technique for determining whether the tumor has spread outside the chest. Your doctor may order a variety of tests to determine the stage of your tumor. The results of these tests will help determine which therapy will be the most appropriate for your tumor. Non- invasive tests usually involve medical imaging or blood testing. Invasive tests are those that involve a minor surgical procedure or a image-guided biopsy. Non-Invasive Tests Serum Mesothelin – Measures blood levels of a protein secreted by certain mesotheliomas. Chest X-Ray – Defines extent of tumor within the chest. CT scan – Defines extent of tumor but gives more detailed information than chest x-ray MRI – Useful if chest wall invasion suspected on CT scan. PET scan – Very useful for determining whether tumor has spread to other organs outside of the chest. Non-Invasive Tests CT-guided core biopsy –Diagnosis of mesothelioma. Outpatient procedure. Thoracentesis – Outpatient evaluation of fluid from chest. Diagnostic only 30% of the time. Thoracoscopy – The most accurate method of diagnosing mesothelioma. Involves general anesthetic and a small incision on the chest. Mediastinoscopy – Outpatient surgical procedure to evaluate if lymph glands in the center of the chest contain tumor. Involves a small incision on the neck. Endobronchial ultrasound needle biopsy – Outpatient procedure that evaluates if lymph glands in the center of the chest contain tumor. Does not involve surgery. Laparoscopy – Outpatient surgical procedure to evaluate if tumor has spread to the abdomen. Surgical Staging In patients who are deemed candidates for surgery based on non-invasive tests, surgical staging is usually performed to ensure that tumor does not involve the lymph glands or the abdomen. This involves a single, short outpatient anesthetic where laparoscopy and endobronchial ultrasound guided fine needle aspiration are performed simultaneously. Occasionally thoracoscopy may be required to obtain additional tumor tissue to confirm the diagnosis of mesothelioma. In this case patients usually stay over night in hospital and go home the following day.
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