Patterns of local and nodal failure in malignant pleural mesothelioma after extrapleural pneumonectomy and photon-electron radiotherapy

Introduction: Multimodality therapy including extrapleural pneumonectomy (EPP), chemotherapy, and radiotherapy (RT) is often recommended for fit patients with early stage malignant pleural mesothelioma. Planning RT after an EPP is difficult due to the large target area, the high doses required to prevent recurrence, and the proximity of critical structures. We studied patterns of local and nodal recurrence in patients treated at our institution with EPP and RT, and whether advanced treatment planning techniques, such as intensity modulated radiotherapy (IMRT), could have been of potential benefit. Methods: From 1993 to 2008, 86 patients with malignant pleural mesothelioma underwent EPP followed by hemithoracic RT (median dose: 54 Gy). The RT technique included a combination of photons and electrons to maximize dose to the target, whereas minimizing dose to normal tissues. After treatment, patients were followed with serial imaging and patterns of local and nodal failure were studied. Results: Median follow-up time for 78 analyzed patients was 17 months. Eight percent were in stage I, 35% stage II, 55% stage III, and 2% stage IV. Ten percent of all patients developed late grade 3 pulmonary toxicity and no patient died of RT. Fifteen patients failed in local and/or nodal sites and did not have a distant component to their failure pattern. Of these 15 patients, 10 failed in regions of dose inhomogeneity and could have possibly benefited from IMRT. Conclusions: The photon-electron technique was tolerable, but IMRT may provide better target coverage in some patients. IMRT's advantages must be balanced against the increased risk of fatal pulmonary toxicity.