Mesothelioma Lung Cancer
Pleural Mesothelioma is the only identified pleural cancer and is caused by asbestos exposure in almost all cases.
- Asbestos workers have up to a 10% lifetime risk of developing the disorder, with an average latency of 30 years.
- Risk is independent of smoking. Mesothelioma can spread locally, or it can metastasize to the hilar and mediastinal lymph nodes, pericardium, diaphragm, peritoneum, liver, adrenals, or kidneys and, rarely, the tunica vaginalis of the testes.
SIGNS AND SYMPTOMS OF MESOTHELIOMA
Patients most often present with dyspnea and non-pleuritic chest pain. Constitutional symptoms are uncommon at presentation. Invasion of the chest wall and other adjacent structures may cause severe pain, hoarseness, dysphagia, Homer syndrome, brachial plexopathy, or ascities.
DIAGNOSIS OF MESOTHELIOMA
- Chest x-ray
- Pleural fluid cytology or pleural biopsy
- Sometimes, video- assisted thoracoscopic surgery (VATS) or thoracotomy
- Staging with chest CT, Mediastinoscopy, and MRI, or sometimes with PET scan and bronchoscopy
The pleural form of mesothelioma, which represents more than 90% of all cases ( the other 10% include pericardial and peritoneal mesotheliomas), appears on x-ray as diffuse unilateral or bilateral pleural thickening that appears to encase the lungs, usually producing blunting of the costophrenic angles. Pleural effusions are present in 95% of cases and are typically unilateral, large, and hemorrhagic. Diagnosis is based on pleural fluid cytology or pleural biopsy. If diagnosis is not certain after these procedures, biopsy by VATS or thoracotomy is done
Chest CT, Mediastinoscopy, and MRI are usually used for staging. Sensitivity and specificity and MRI and CT are comparable, although MRI is helpful on determining tumor extension into the spine or spinal cord. PET may have better sensitivity and specificity for distinguishing benign from malignant pleural thickening. Bronchoscopy should be done to rule out coexisting endobronchial lung cancers. Increased levels of hyaluronidase in pleural fluid are suggestive but not diagnostic of mesothelioma. Soluble mesothelin-related proteins released into the serum by mesothelial cells are being studied as possible tumor markers for disease detection and monitoring, but the false-positive rate may limit their effectiveness.
TREATMENT OF MESOTHELIOMA
- Supportive care
- Pleurodesis or pleurectomy for pleural effusions and relief of dyspnea
- Analgesia with opioids and sometimes radiation therapy
- Chemotherapy for tumor shrinkage and symptom relief
- Experimental therapies
Complete surgical resection usually is not practical. Premtrexed (an antifolate antimetabolite) and Cisplatin combination shows some good results but warrants further study.
The major focus of treatment is supportive care and relief of pain and dyspnea. Given the diffuse nature of the disorder, radiation therapy is usually not suitable except to treat localized pain and for needle- tract metastases. It is not commonly used for treatment of nerve root pain. To help reduce dyspnea caused by pleural effusions, pleurodesis or pleurectomy can be used. Adequate analgesia is important but difficult to achieve. Usually opioids, both transdermal and delivered via indwelling epidural catheters, are used. Chemotherapy using cisplatin and gemcitabine relieves symptoms in most cases and sometimes decreases tumor size. Multimodality therapies are advocated by some authorities. Intrapleural injection of granulocyte- macrophage colony- stimulating factor or interferon –y1b, IV ranpirnase (a ribonuclease), and gene therapies are under study.
PROGNOSIS OF MESOTHELIOMA
Mesothelioma remains an incurable cancer, and long-term survival is very rare. Surgery to remove the pleura, ipsilateral lung, phrenic nerve, hemidiaphragm and pericardium combined with chemotherapy and radiation therapy may be done, however it does not significantly change prognosis or survival time. No treatment substantially prolongs survival. Survival from time of diagnosis averages 8 to 15 months, depending on the location and cell type. A few patients, usually younger patients with shorter duration of symptoms, have more favorable prognosis, sometimes surviving for several years after diagnosis.
OTHER ASBESTOS- RELATED PLEURAL DISEASE
Pleural disease is a hallmark of asbestos exposure; it includes formation of pleural plaques, calcification, thickening, rounded atelectasis, adhesions, effusion, and mesothelioma,
Pleural disease generally produces effusion but with few symptoms. All pleural changes are diagnosed by chest x-ray or CT, though chest CT is more sensitive that chest x-ray for detecting pleural disorders. Treatment is seldom needed except for cancer.
Discrete plaques, which occur in up to 60% of workers exposed to asbestos, normally affect the bilateral parietal pleurae between the 5th and 9th ribs and adjacent to the diaphragm. Generally, plaque calcifications are common which can lead to misdiagnosis of severe pulmonary disease when radiographically superimposed on lung fields. CT can distinguish pleural from parenchymal disease in this setting. Fat stripes may be mistake for pleural plaques on chest x-ray. Also, CT scan can distinguish pleural disease from far artifact.
Diffuse thickening affects visceral as well as parietal plurae. It may be an extension of pulmonary fibrosis from parenchyma to the pleurae or a non specific reaction to pleural effusion. With or without calcification, pleural thickening can cause a restrictive defect.
Rounded atelectasis is a benign symptom of pleural thickening in which invagination of pleura into the parenchyma can entrap lung tissue, causing atelectasis. On chest x-ray and CT, it normally appears as a curvilinear cicatricial mass, often in the lower lung zones, and can be confused with a pulmonary cancer.
Pleural effusions occur but are less common that the other pleural changes they accompany. These benign effusions are usually bilateral, exudative, and often hemorrhagic. They usually resolve spontaneously. <END> Mesothelioma Cancer