PURPOSE: Intensity Modulated Radiation Therapy (IMRT) can significantly improve local control of malignant pleural mesothelioma following extrapleural pneumonectomy (EPP). Recently concerns have been raised regarding the risk of radiation injury to the contralateral lung. The purpose of this study was to investigate the incidence of fatal pulmonary events following IMRT and EPP.
METHODS: We retrospectively reviewed 63 consecutive patients with mesothelioma who underwent EPP and IMRT (median dose 45 Gy). Endpoints were any pulmonary-related death (PD) and non-cancer death (NCD). PD was defined as death within 6 months of IMRT from pneumonia or pneumonitis. NCD included deaths from all other causes excluding PD and cancer. V5, V10 and V20 were defined as the percent volume of contralateral lung receiving 5, 10 and 20 Gy respectively.
RESULTS: There were 6 (10%) deaths from PD (pneumonia 4; pneumonitis 2). 7 (11%) patients died from NCD. 3 of these patients died from non-parenchymal pulmonary causes including embolus (2) and sepsis following bronchopleural fistula (1). 4 patients died from unknown causes, but had no radiographic evidence of either pulmonary disease or recurrent cancer. Patients with PD received significantly more radiation to the contralateral lung (Table). On univariate analysis, factors identified to predict PD included lower preoperative ejection fraction (p=0.021), V10 (p=0.032), V20 (p=0.002), volume of lung spared ≥ 10Gy (p=0.025), and mean lung dose (0.013). On multivariate analysis, only V20 was significant for PRD (p=0.017, odds ratio 1.50, CI 1.08-2.08) and NCD (p=0.033, odds ratio 1.21, CI 1.02-1.45).analysis, only V20 was significant for PRD (p=0.017, odds ratio 1.50, CI 1.08-2.08) and NCD (p=0.033, odds ratio 1.21, CI 1.02-1.45).
CONCLUSION: Fatal pulmonary-related events following IMRT after EPP are associated with the amount of radiation received by the contralateral lung. The V20 at which no PD occurred (5%) was considerably lower than the value accepted during standard thoracic radiation therapy (35%).
CLINICAL IMPLICATIONS: In the post-pneumonectomy setting, radiation exposure to the contralateral lung should be limited, and V20 should be kept below 5%.
DISCLOSURE: David Rice, None.