BACKGROUND: Approximately 30 patients with malignant mesothelioma following radiotherapy have been described. Population-based studies of this occurrence have not been reported. METHODS: Patients with malignant mesothelioma of the pleura were collected. All of the patients had a prior cancer and had received radiotherapy to the region in which the malignant mesothelioma developed. Data from the National Cancer Institute's Surveillance, Epidemiology and End Results Program and the Connecticut Tumor Registry were evaluated for cases of malignant mesothelioma of the pleura occurring in patients with a previous cancer. The literature on post-irradiation malignant mesotheliomas was reviewed. RESULTS: Eight patients (4 men, 4 women) with malignant mesothelioma occurring in sites of radiotherapy for a prior tumor were identified. The mean age at diagnosis of mesothelioma was 45 years (range: 22-78 years), and the average interval between radiotherapy and the mesothelioma was 21 years (range: 11-29 years). Three of the patients had also received chemotherapy. Histologically, the mesotheliomas were epithelial in five cases, biphasic in one, and sarcomatous in one. One hundred forty-two patients were identified in the epidemiologic survey. The majority were men (89%), with a mean age for all patients of 68.5 years (range: 35-86 years) and a median latency between first cancer and mesothelioma of 4.3 years (range: 2 months-29.9 years). CONCLUSIONS: Mesotheliomas rarely develop as second malignant neoplasms. Within a large, population-based survey of patients with cancer, temporal patterns and demographic features of most second primary mesotheliomas were similar to asbestos-related tumors, although the late effects of cancer treatment might have contributed to the occurrence of cancer in some patients.
