External beam radiation therapy for the treatment of pleural mesothelioma.

Technical challenges in the treatment of pleural mesothelioma with radiotherapy remain. When there is limited or no resection of disease, delivery of high-dose RT to the entire hemithorax in the setting of an intact lung has not been shown to be associated with any survival benefit, and the toxicity is clearly significant. Conversely, the use of palliative RT delivered to limited fields (less than hemithorax) can provide pain relief in 50% to 70% of cases. After pleurectomy and decortication, delivery of a tumoricidal dose of radiation to potential microscopic mesothelioma is similarly problematic. Details of various sophisticated radiation techniques, such as photon and electron matching, intraoperative RT, and the use of multiple small treatment beams using IMRT, have been published, and the former two techniques have been used. Although these approaches are innovative and creative, they have significant limitations in terms of the total dose that can be delivered, dose homogeneity, and the ability to cover fully all the areas at risk (e.g., fissures). Finally, implementation of RT after EPP permits delivery of higher doses than in the post-pleurectomy setting using treatment techniques such as photon/electron matching and IMRT. The dosimetry remains limited by the surrounding normal structures (heart and liver, particularly). Studies have shown that it is feasible to deliver nominal doses of 50 to 54 Gy after EPP, and local control rates have improved . Although the target volumes may not be covered fully by these doses, it is a significant improvement over lower dose treatment plans. In the future, it is reasonable to continue to pursue aggressive surgical resection with EPP and further refine these complex radiotherapy techniques. Treatment with novel agents, such as alimta, in the neoadjuvant setting also may further enhance local and systemic control of pleural mesothelioma.