title: Compensator-based intensity-modulated radiation therapy for malignant pleural mesothelioma post extrapleural pneumonectomy.
abstract: The present work investigated the potential of compensator-based intensity-modulated radiation therapy (CB-IMRT) as an alternative to multileaf collimator (MLC)-based intensity-modulated radiation therapy (IMRT) to treat malignant pleural mesothelioma (MPM) post extrapleural pneumonectomy. Treatment plans for 4 right-sided and 1 left-sided MPM post-surgery cases were generated using a commercial treatment planning system, XIO/CMS (Computerized Medical Systems, St. Louis, MO). We used a 7-gantry-angle arrangement with 6 MV beams to generate these plans. The maximum required field size was 30 x 40 cm. We evaluated IMRT plans with brass compensators (.Decimal, Sanford, FL) by examining isodose distributions, dose-volume histograms, metrics to quantify conformal plan quality, and homogeneity. Quality assurance was performed for one of the compensator plans. Conformal dose distributions were achieved with CB-IMRT for all 5 cases, the average planning target volume (PTV) coverage being 95.1% of the PTV volume receiving the full prescription dose. The average lung V20 (volume of lung receiving 20 Gy) was 1.8%, the mean lung dose was 6.7 Gy, and the average contralateral kidney V15 was 0.6%. The average liver dose V30 was 34.0% for the right-sided cases and 10% for the left-sided case. The average monitor units (MUs) per fraction were 980 MUs for the 45-Gy prescriptions (mean: 50 Gy) and 1083 MUs for the 50-Gy prescriptions (mean: 54 Gy). Post surgery, CB-IMRT for MPM is a feasible IMRT technique for treatment with a single isocenter. Compensator plans achieved dose objectives and were safely delivered on a Siemens Oncor machine (Siemens Medical Solutions, Malvern, PA). These plans showed acceptably conformal dose distributions as confirmed by multiple measurement techniques. Not all linear accelerators can deliver large-field MLC-based IMRT, but most can deliver a maximum conformal field of 40 x 40 cm. It is possible and reasonable to deliver IMRT with compensators for fields this size with most conventional linear accelerators.
authors.affiliation: Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, and Radiation Oncology, Tampa, Florida, U.S.A.
authors.forename: Khosrow
authors.initials: K
authors.lastname: Javedan
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute at the University of South Florida, Tampa, Florida, U.S.A.
authors.forename: Craig W
authors.initials: CW
authors.lastname: Stevens
authors.affiliation: H. Lee Moffitt Cancer Center and Research Institute at the University of South Florida, Tampa, Florida, U.S.A.
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Forster
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology; D008654:Mesothelioma / Q000473:pathology / Q000532:radiotherapy*; D010315:Particle Accelerators; D010997:Pleural Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011013:Pneumonectomy / Q000379:methods; D011786:Quality Control; D011859:Radiography; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results