Hemithoracic radiotherapy after extrapleural pneumonectomy for malignant pleural mesothelioma: A dosimetric comparison of two well-described techniques

Introduction: Extrapleural pneumonectomy (EPP) with adjuvant radiotherapy may be used to treat malignant pleural mesothelioma. Radiation pneumonitis, felt to be related to contralateral lung radiation dose, may affect patient mortality in this setting. Two standard therapeutic approaches currently used to deliver adjuvant radiotherapy were compared in this study: intensity modulation radiation treatment (IMRT) with a planned dose of 45 Gray (Gy) and a modified electron-photon technique delivering 54 Gy. Methods: Treatment plans of 10 mesothelioma patients who underwent EPP and hemithoracic IMRT to a total dose of 45 Gy were analyzed. Plans using a combination of opposed anterior posterior radiation fields and electron supplementation (electron-photon technique [EPT]) to a total dose of 54 Gy were then generated and compared with IMRT plans. Results: Dosimetric comparison revealed a significant reduction in contralateral lung dose with EPT versus IMRT, even with increased prescription dose used with EPT plans. Median heart and contralateral kidney doses were also significantly reduced with EPT versus IMRT. Dose coverage of planning target volume and doses to spinal cord, liver, and ipsilateral kidney were similar with use of the two techniques. ConclusionS: Our data suggest that hemithoracic radiotherapy delivered after EPP using EPT may minimize dose to contralateral lung and other structures when compared with IMRT, without compromise of planning target volume coverage.