BACKGROUND - Malignant pleural mesotheliomas (MPMs) are rare tumors that usually have a fatal outcome. The association of these tumors with asbestos exposure is well established. Induction of malignant mesothelioma by nonasbestos-related causes also has been reported in the literature, although the number of documented cases is extremely small. Two additional patients with malignant pleural mesothelioma many years after radiotherapy for breast cancer are reported.
METHODS - The observations as reported in the literature on the involvement of radiation in the development of MPMs are reviewed and compared with the authors' clinical experience. In a retrospective random review, 1000 patients who received thoracic irradiation at M. D. Anderson Cancer Center were studied for histologic and radiographic evidence of MPM. The selection criteria included the development of a unilateral pleural effusion years after successful treatment with thoracic irradiation for a proven malignancy. Patients with a history compatible with asbestos exposure were excluded from the review.
RESULTS - There have been only three previous cases of documented MPM associated with thoracic irradiation reported in the English literature. A review of the experience at our institution has demonstrated three patients with radiation-induced MPM. One patient has been reported elsewhere. Details of the other two patients are discussed in this paper.
CONCLUSIONS - Nonasbestos-related causes of MPMs are rare. The additional two patients lend added support to the association between thoracic irradiation and the development of MPM. The development of a unilateral pleural effusion occurring years after successful treatment of a proven malignancy with thoracic irradiation should alert the clinician to the possibility of MPM.