Asbestos- uses, dangers, disposal…

A mesothelioma patient frequently forgets his or her contact with asbestos. To track down the source of asbestos exposure, obtain a detailed work history, beginning with the first job the patient held; ask about materials the patient and his fellow workers used.

Positive identification of asbestos exposure significantly helps to clarify clinical and radiologic suspicion, as well as pathologic diagnosis of mesothelioma, gastrointestinal cancer, or lung cancer. Also file a report of work injury. An individual should be compensated for medical expenses and disability due to a hazardous work environment that has subjected him to high risk or to diseases such as mesothelioma.

Although a cure for pleural mesothelioma–stage I, or carcinoma in situ–is associated with a five-year survival o’70-100 percent. Thus, identifying workers at high risk from asbestos, through periodic chest X-ray study and sputum cytology, is merited.

It also is important to screen a potentially hazardous work environment for epidemiologic information. Hazardous materials then can be identified and inhalational exposure controlled by suitable respiratory exhaust ventilation, and substitution of other materials for asbestos. Waiting for signs and/or symptoms of cancer to appear is waiting far too long.

“Treatment for malignant mesothelioma remains investigational. . .. Radical surgery, such as pleuropneumonectomy for patients who have pleural mesothelioma, in the majority of patients is not curative.”

Early diagnosis of malignant mesothelioma is difficult. A patient often presents with an isolated pleural effusion of unknown etiology; pleural thickening or scalloping may be absent. Pleural cytology and needle biopsy rarely are diagnostic.

A recent review of our experience at Mount Sinai Hospital indicates that the diagnosis of malignant mesothelioma was delayed for more than six months in 25 percent of patients. Many patients were observed during several months or received treatment for suspected tuberculosis, rheumatoid arthritis, or lupus.

Three diagnostic steps are important. First, suspect the diagnosis. The most helpful hint is a history of past asbestos exposure. Be sure to list the dates and durations of the patient’s jobs when taking a careful occupational history. Temporary employment such as summer jobs while in high school or college and activities during World War II are impotant. It took six months for one of my patients to remember that she had been exposed to asbestos; only when she discussed the matter with an old friend did they both recall having worked in a factory 40 years previously insulating electric wires with asbestos.

When a history of occupational exposure is absent, explore the possibility of environmental or familial exposure to asbestos, such as residential proximity to shipyards or asbestos factories. I have seen several patients below age 40 with mesothelioma who were exposed to asbestos as children through the work clothes of a family member, usually the father. Cigarette smoking does not appear to increase the risk of malignant mesothelioma, although it seems to act synergistically with asbestos to induce lung cancer .

Second, obtain an adequate biopsy specimen for diagnosis. Usually this requires an open surgical approach, such as thoracotomy or laparotomy, although thoracoscopy or laparoscopy may be substituted at an early stage when serosal thickening still is minimal. When the pathologic features are characteristic–as in mixed (biphasic) mesothelioma, where both epithelial and fibrosarcomatous elements are present–the diagnosis is established. The majority of cases of mesothelioma, however, are epithelial (tubulopapillary) and quite often are confused with a metastatic adenocarcinoma in the lung, breast, pancreas, or in the ovaries.

Third, confirm the diagnosis by ruling out another primary tumor and obtaining special stains. The absence of mucin (as indicated by muciearmine stain or the periodic acid-Schiff stain) and the presence of hyaluronic acid (as indicated by colloidal iron or Alcian blue stains), followed by hyaluronidase digestion, are characteristic of epithelial mesothelioma. If doubt persists, a repeat biopsy or electron microscopy may become necessary.

Treatment for malignant mesothelioma remains investigational. A staging system based on the tumor, nodes, metastasis (TNM) classification has been proposed.

Radical surgery, such as pleuropneumonectomy for patients with pleural mesothelioma, usually is not curative. But palliative surgery such as pleural decortication may be beneficial, particularly in patients with recurrent pleural effusion. radiotherapy often is disappointing, partly because the extent of disease would requires very large radiation fields. And clinical experience with chemotheraly–doxorubicin HCl Adriamycin has been the most commonly employed agent–is limited.

Malignant mesotheliomas are staged surgically as follows:

Stage 1–tumor confined to one hemithorax or to the peritoneal cavity Stage 2–tumor involving the chest wall: mediastinum, pericardium, or the contra-lateral pleura. Stage 3–tumor in both thorax and abdomen or in lymph nodes outside the chest Stage 4–distant bloodborne metastases.

While the extent of disease cannot be accurately delineated on a flat chest film, the characteristic orange-peel appearance and mediastinal involvement can frequently be seen clearly on CT scan. The CT scan is used increasingly for staging.

Mesothelioma encases the lung, preventing proper expansion, but direct invasion of the lungs is not usually encountered. In early stage 1, the peel is relatively thin, and it is sometimes possible merely to peel the pleura from the lung without doing a pneumonectomy.

More extensive resection is usually necessary with a thicker tumor. Beyond stage 1, the tumor is more difficult to resect, and the attempt is made only occasionally.

Mesothelioma is a highly malignant, almost invariably lethal tumor regardless of histologic type. Survival time appears to correlate with the stage of disease. But even patients with stage 1 disease–the majority–do not have a good prognosis. The typical mesothelioma survival rate with stage 1 or 2 disease generally die within two years.

Virtually the average mesothelioma patient with stage 3 disease are dead within one year, with a median survival of only six months. Almost half of patients have no known history of asbestos exposure; however, there is no correlation of exposure or site of the primary lesion with prognosis.

In general, the longer the duration of symptoms before diagnosis, the better the prognosis–that is, indolent tumors remain slow growing. Degree of dyspnea is apparently dependent upon the amount of pleural effusion, in addition to tumor volume; a small amount of tumor may be associated with a large pleural effusion. The degree of pain appears to be related to invasion of the chest wall, denoting a more aggressive tumor.

The most frequent cause of death from mesothelioma is respiratory failure, mainly because the disease in almost half of patients remains localized to the chest. Pleural mesothelioma is bilateral at presentation in fewer than 5 percent of patients. Spread to the opposite lung or into the abdomen–bowel obstruction also may be a cause of death–does not usually occur until late in the disease course.

Small bowel obstruction is the most frequent cause of death resulting from primary peritoneal mesotheliomas. Patients with pericardial or cardiac involvement may die of arrhythmia, congestive heart failure, or, if vessels are compromised, a myocardial infarct.