Physics Contribution Generalizable Class Solutions for Treatment Planning of Spinal Stereotactic Body Radiation Therapy David C. Weksberg, M.D., Ph.D.,* Matthew B. Palmer, B.S., M.B.A.,* Khoi N. Vu, B.S.,* Neal C. Rebueno, B.S.,* Hadley J. Sharp, M.D.,* Dershan Luo, Ph.D., y James N. Yang, Ph.D., y Almon S. Shiu, Ph.D., y Laurence D. Rhines, M.D., z Mary Frances McAleer, M.D., Ph.D.,* Paul D. Brown, M.D.,* and Eric L. Chang, M.D. x Departments of *Radiation Oncology, y Radiation Physics, and z Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, Texas; and x Department of Radiation Oncology, University of Southern California Keck School of Medicine, Norris Cancer Hospital, Los Angeles, California Received Aug 22, 2011, and in revised form Dec 12, 2011. Accepted for publication Dec 14, 2011 Summary Producing high-quality treatment plans for spinal stereotactic body radiation therapy (SBRT) is difficult and time-consuming. Class solutions are presented for novel intensity-modulated radiation therapy for spinal SBRT, incorporating a plan- ning clinical target volume (pCTV) quality metric. Use of class solutions generates superior treatment plans with respect to target coverage, conformality, and integral dose. The class solution approach also affords substantial improvements in planning efficiency, Purpose: Spinal stereotactic body radiation therapy (SBRT) continues to emerge as an effective therapeutic approach to spinal metastases; however, treatment planning and delivery remain resource intensive at many centers, which may hamper efficient implementation in clinical prac- tice. We sought to develop a generalizable class solution approach for spinal SBRT treatment planning that would allow confidence that a given plan provides optimal target coverage, reduce integral dose, and maximize planning efficiency. Methods and Materials: We examined 91 patients treated with spinal SBRT at our institution. Treatment plans were categorized by lesion location, clinical target volume (CTV) configura- tion, and dose fractionation scheme, and then analyzed to determine the technically achievable dose gradient. A radial cord expansion was subtracted from the CTV to yield a planning CTV (pCTV) construct for plan evaluation. We reviewed the treatment plans with respect to target coverage, dose gradient, integral dose, conformality, and maximum cord dose to select the best plans and develop a set of class solutions. Results: The class solution technique generated plans that maintained target coverage and improved conformality (1.2-fold increase in the 95% van’t Riet Conformation Number describing the conformality of a reference dose to the target) while reducing normal tissue inte- gral dose (1.3-fold decrease in the volume receiving 4 Gy (V 4Gy ) and machine output (19% monitor unit (MU) reduction). In trials of planning efficiency, the class solution technique reduced treatment planning time by 30% to 60% and MUs required by w20%: an effect inde- pendent of prior planning experience. Conclusions: We have developed a set of class solutions for spinal SBRT that incorporate a pCTV metric for plan evaluation while yielding dosimetrically superior treatment plans with Reprint requests to: Eric L. Chang, M.D., Radiation Oncology Department, USC Keck School of Medicine, USC/Norris Cancer Hospital, 1441 Eastlake Avenue NOR G-356, Los Angeles, CA 90033. Tel: (323) 865-3072; Fax: (323) 865-3037; E-mail: eric.L.chang@usc.edu or echang@mdanderson.org Conflict of interest: none. Supplementary material for this article can be found at www.redjournal.org. Int J Radiation Oncol Biol Phys, Vol. 84, No. 3, pp. 847e853, 2012 0360-3016/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.ijrobp.2011.12.060 Radiation Oncology International Journal of biology physics www.redjournal.org