Compensator‐based intensity‐modulated radiation therapy for malignant pleural mesothelioma post extrapleural pneumonectomy

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 [Formula: see text]. 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 [Formula: see text] (volume of lung receiving 20 Gy) was 1.8%, the mean lung dose was 6.7 Gy, and the average contralateral kidney [Formula: see text] was 0.6%. The average liver dose [Formula: see text] 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 [Formula: see text]. It is possible and reasonable to deliver IMRT with compensators for fields this size with most conventional linear accelerators. PACS numbers: 87.56.ng, 87.56.N, 87.55.D, 87.55.dk