Original paper Treatment plan comparison between stereotactic body radiation therapy techniques for prostate cancer: Non-isocentric CyberKnife versus isocentric RapidArc Yu-Wei Lin a, b, c, * , Kuei-Hua Lin a , Hsiu-Wen Ho a , Hsiu-Man Lin a , Li-Ching Lin a, d , Steve P. Lee e , Chen-Shou Chui f a Department of Radiation Oncology, Chi Mei Medical Center, Tainan, Taiwan b Institute of Biomedical Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan c School of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan d School of Medicine, Taipei Medical University, Taipei, Taiwan e Department of Radiation Oncology, David Geffen School of Medicine of The University of California Los Angeles, Los Angeles, CA, USA f Department of Medical Physics, Koo Foundation Sun Yat-Sen Cancer Center, Taipei, Taiwan article info Article history: Received 5 January 2014 Received in revised form 18 March 2014 Accepted 19 March 2014 Available online xxx Keywords: Prostate cancer Stereotactic body radiation therapy Volumetric modulated arc therapy CyberKnife RapidArc abstract Purpose: The aim of this study was to evaluate the feasibility and dose distribution of two different stereotactic body radiation therapy (SBRT) techniques, isocentric RapidArc (RA) and non-isocentric CyberKnife (CK), for the treatment of localized prostate cancer. Methods: Two groups of patients (Groups 1 and 2 with ten patients per group) treated with CK were re- planned with RA. The patients were grouped according to the rectum constraint used (Group1, maximum dose for rectum; Group 2, doseevolume histogram for rectum). The prescription dose was 37.5 Gy in five fractions. The two SBRT techniques were compared by target coverage, normal tissue sparing, and dose distribution parameters. Monitor units (MUs) and the delivery time were likewise compared to assess delivery efficiency. Results: The RA plans consistently exhibited superior PTV coverage and better rectum sparing at low doses in the both groups. The conformity and heterogeneity indices of the RA plans were better than the CK plans. Additionally, the RA plans resulted in fewer low-dose regions, lower MUs, and faster delivery times than the CK plans. Conclusions: The good dosimetric distribution and shorter delivery time make RA an attractive SBRT technique for the treatment of localized prostate cancer. Ó 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved. Introduction Stereotactic body radiation therapy (SBRT) is an external beam radiation therapy method used to very precisely deliver a high dose of radiation to an extracranial target within the body, using either a single dose or a small number of fractions. The major features of SBRT are the accurate delivery of high doses to the target area and the rapid tapering of dose delivery away from the target area. Combined with radiobiology, the use of SBRT may result in a higher biological effective dose for prostate cancer and may achieve a higher therapeutic benefit [1e4]. Recently, researchers using SBRT, including the CyberKnife (CK, Accuray, Sunnyvale, CA, USA) technique, have achieved promising clinical results in the treatment of prostate cancer [5e8]. The CK stereotactic radiotherapy system is an accurate image-guided method for delivering radiation to a precisely targeted area using multiple non-isocentric beams with steep surrounding-dose gra- dients [9]. RapidArc (RA, Varian Medical System, Palo Alto, CA, USA) is a volumetric-modulated arc radiotherapy (VMAT) technique that can deliver highly conformal, intensity-modulated radiation doses by a single or multiple rotations of the gantry of the linear accel- erator [10]. RA allows achieving treatment plans of similar or improved quality compared to fixed-field intensity-modulated ra- diation therapy while reducing the treatment time per fraction [11]. * Corresponding author. Department of Radiation Oncology, Chi Mei Medical Center, No.901, Jhonghua Rd., Yongkang Dist., Tainan City 71004, Taiwan. Tel.: þ886 6 2812811x53501; fax: þ886 6 2850049. E-mail address: marklin1108@gmail.com (Y.-W. Lin). Contents lists available at ScienceDirect Physica Medica journal homepage: http://www.physicamedica.com http://dx.doi.org/10.1016/j.ejmp.2014.03.008 1120-1797/Ó 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved. Physica Medica xxx (2014) 1e8 Please cite this article in press as: Lin Y-W, et al., Treatment plan comparison between stereotactic body radiation therapy techniques for prostate cancer: Non-isocentric CyberKnife versus isocentric RapidArc, Physica Medica (2014), http://dx.doi.org/10.1016/j.ejmp.2014.03.008