Non-Malignant Asbestos Diseases at Greater Risk of Developing Asbestos Cancer
September 24, 2004 - The American Thoracic Society (ATS) has updated its guidelines for diagnosing patients with nonmalignant (non-cancerous) diseases caused by asbestos exposure ( Am J Respir Crit Care Med. 2004 Sep 15; 170(6): 691-715, available from National Library of Medicine for a small fee). These conditions affect breathing, lung capacity, and the quality of life. They include asbestosis, airflow obstruction, pleural thickening or pleural fibrosis, and pleural effusions (buildup of fluid in the pleural area). The pleura is the membrane covering the lungs and the chest cavity.
Doctors should consider three factors when making a diagnosis, according to the ATS:
- results from imaging tests (X-rays, CT scans) and histology (examination of tissues or samples under the microscope);
- the patient's occupation and history of asbestos exposure; and
- whether other causes for the illness may be excluded.
If these factors point to a diagnosis of an asbestos disease, then the doctor must determine how severely the patient is impaired.
Typically, nonmalignant asbestos diseases take at least 15 years to develop; although some who were exposed to extremely high levels of asbestos became ill within months. For example, shipyard workers who applied insulation in confined spaces developed asbestosis after brief periods of heavy exposure. Such cases of extreme exposure are becoming rare.
Exercise testing and the presence of disease symptoms are not necessary to make the initial diagnosis of a nonmalignant asbestos disease, the ATS report states. A chest X-ray is still considered useful for discovering pleural plaques or fluid in the pleural spaces. A high-resolution computed tomography scan (HRCT) is now the standard method for diagnosing asbestosis. A computed tomography or CT scan is a radiographic technique that uses a computer to combine multiple X-ray images into a two dimensional cross-sectional X-ray image. The computer turns the information into a detailed picture. An HRCT is more precise than a conventional CT scan. It uses a narrower X-ray beam and a high spatial frequency reconstruction to provide extremely high definition images of the lungs.
Patients with nonmalignant asbestos-related illnesses are at increased risk for developing cancers such as lung cancer and mesothelioma, an aggressive disease that attacks the membranes around the lungs, chest, or abdomen. Patients should have X-rays and pulmonary function tests every three to five years, periodic screening for colon cancer, and be carefully monitored for signs of lung cancer or mesothelioma, the ATS advises. Doctors should encourage patients with asbestos diseases to quit smoking. Smoking aggravates the lungs, and often leads to lung cancer. The combination of tobacco and asbestos exposure greatly increases the smoker's chances of developing the disease.
Asbestos Exposure is Still Too Common
The ATS estimates that asbestos remains a hazard for 1.3 million workers in the construction industry and for those involved in maintenance of asbestos-containing buildings, equipment, and older appliances. New products that may contain asbestos include brake pads, roofing materials, vinyl tile, and imported cement pipe and sheeting. Asbestos may also be present in insulation, especially vermiculite insulation found in some homes (see Tremolite Asbestos in Vermiculite Mines, Vermiculite Asbestos Attic Insulation).
Deaths in the United States from asbestosis increased 400% during the last two decades, according to the federal Centers for Disease Control and Prevention. Recently, a study by the Environmental Working Group found that about 10,000 deaths per year nationwide are due to asbestos exposure. The report included deaths from mesothelioma, asbestosis, gastrointestinal (GI) cancers, and asbestos-related lung cancers. It was based on government death certificates, statistics, and population studies. Sadly, the rate of asbestos diseases is not expected to decrease in the coming years because workers and their families continue to be exposed to asbestos products. Also, asbestos diseases usually take decades to develop.
Asbestos diseases are incurable, and treatment involves improving the quality of life. The shortness of breath experienced by asbestosis victims may be treated with inhaled or oral medicines called bronchodilators. They open up the bronchial tubes and allow better air passage. Patients may also use an ultrasonic, mist humidifier to loosen bronchial secretions so that they can be expelled through coughing. In severe cases of asbestosis, supplemental oxygen may be required.
Mesothelioma is a fatal disease. The aim of mesothelioma therapy is to decrease pain and increase survival time. Surgery may be helpful if the patient is otherwise healthy enough to withstand its rigors. An "extrapleural pneumonectomy" removes portions of the lung, the lining of the lung, the lining of the heart, and the diaphragm. This radical mesothelioma treatment can remove cancer cells, and may slow the progress of the disease.
Chemotherapy and radiation treatment may slow the rate of tumor growth. These procedures are used to treat both mesothelioma and asbestos-related lung cancer. A chemotherapy drug, pemetrexed (Alimta®), has recently been approved to treat advanced non-small cell lung cancer in patients who have already undergone chemotherapy without success. Alimta® plus a platinum compound, cisplatin, has been approved to treat pleural mesothelioma, the form of the disease that affects the membrane surrounding the lungs and chest. It is prescribed for mesothelioma patients when surgery is not an option. Pemetrexed attacks cancer cells by inhibiting enzymes that are necessary for cancer cell growth.