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Volumetric Modulated Arc Therapy and Conventional Intensity-modulated Radiotherapy for Simultaneous Maximal Intraprostatic Boost: a Planning Comparison Study

2009; Elsevier BV; Volume: 21; Issue: 5 Linguagem: Inglês

10.1016/j.clon.2009.01.014

1433-2981

Richard Shaffer, William Morris, Vitali Moiseenko, Margaret Welsh, Catherine Crumley, Sandy Nakano, M. Schmuland, Tom Pickles, Karl F. Otto,

Prostate Cancer Diagnosis and Treatment

Aims Volumetric modulated arc therapy (VMAT) is a novel extension of intensity-modulated radiotherapy (IMRT) where an optimised three-dimensional dose distribution may be delivered in a single gantry rotation. This optimisation algorithm is the predecessor to Varian's RapidArc. The aim of this study was to compare the ability of conventional static nine-field IMRT (cIMRT) and VMAT to boost as much of the clinical target volume (CTV) as possible to 88.8 Gy without exceeding organ at risk (OAR) dose-volume constraints. Materials and methods Optimal cIMRT and VMAT radiotherapy plans were produced for 10 patients with localised prostate cancer using common planning objectives: (1) Treat ≥98% of the planning target volume (PTV) to ≥95% of the prescription dose (74 Gy in 37 fractions); (2) keep OAR doses within predefined limits; (3) treat as much of prostate CTV (minus urethra) as possible to ≥120% of prescription dose (=88.8 Gy); (4) keep within maximum dose limits in and out of target volumes; (5) conformality index (volume of 95% isodose/volume of PTV)≤1.2. Results VMAT and cIMRT boosted an average of 68.8 and 63.5% of the CTV to ≥120% of the prescription dose (P=0.002). All dose constraints were kept within predefined limits. VMAT and cIMRT required an average of 949 and 1819 monitor units and 3.7 and 9.6 min, respectively, to deliver a single radiation fraction. Conclusions VMAT is able to boost more of the CTV to ≥120% than cIMRT without contravening OAR dose constraints, and uses 48% fewer monitor units. Treatment times were 61% less than with cIMRT.