Pediatr Blood Cancer 2005;45:304–310

Robotically Guided Radiosurgery for Children Cole A. Giller, PhD, MD,1* Brian D. Berger, MD,1 David A. Pistenmaa, MD,2 Frederick Sklar, MD,4 Bradley Weprin, MD,4 Kenneth Shapiro, MD,4 Naomi Winick, MD,3 Arlynn F. Mulne, MD,3 Janice L. Delp,2 Joseph P. Gilio, PhD,2 Kenneth P. Gall, PhD,2 Karel A. Dicke, MD, PhD,5 Dale Swift, MD,4 David Sacco, MD,4 Kesha Harris-Henderson, MD,2 and Daniel Bowers, MD3 Background. A robotically guided linear accelerator has recently been developed which provides frameless radiosurgery with high precision. Potential advantages for the pediatric population include the avoidance of the cognitive decline associated with whole brain radiotherapy, the ability to treat young children with thin skulls unsuitable for frame-based methods, and the possible avoidance of general anesthesia. We report our experience with this system (the ‘‘Cyberknife’’) in the treatment of 21 children. Procedures. Cyberknife radiosurgery was performed on 38 occasions for 21 patients, age ranging from 8 months to 16 years (7.0  5.1 years), with tumors considered unresectable. Three had pilocytic astrocytomas, two had anaplastic astrocytomas, three had ependymomas (two anaplastic), four had medulloblastomas, three had atypical teratoid/ rhabdoid tumors, three had craniopharyngio-

mas, and three had other pathologies. The mean target volume was 10.7  20 cm3, mean marginal dose was 18.8  8.1 Gy, and mean followup is 18  11 months. Twenty-seven (71%) of the treatments were single-shot and eight (38%) patients did not require general anesthesia. Results. Local control was achieved in the patients with pilocytic and anaplastic astrocytoma, three of the patients with medulloblastoma, and the three with craniopharyngioma, but not for those with ependymoma. Two of the patients with rhabdoid tumors are alive 16 and 35 months after this diagnosis. There have been no procedure related deaths or complications. Conclusion. Cyberknife radiosurgery can be used to achieve local control for some children with CNS tumors without the need for rigid head fixation. Pediatr Blood Cancer 2005;45:304– 310. ß 2004 Wiley-Liss, Inc.

Key words: Cyberknife; pediatric brain tumors; radiosurgery

INTRODUCTION

The advantages of radiosurgery for the treatment of pediatric brain tumors have been recognized for many years, and radiosurgical treatment of children has been successfully implemented at many institutions [2,4,5,7,9– 12,14–16,19,21,23,24,27,28,31,34,36,37]. The popularity of this method is due to the ability of radiosurgical techniques to spare surrounding tissues by focusing the delivered dose onto the tumor, an ability critical to pediatric patients who are prone to devastating cognitive decline following conventional radiotherapy [8,17,18]. A variety of radiosurgical devices have been used to treat children. Frame-based systems such as the Gamma Knife are widely available but require placement of a stereotactic frame anchored to the skull [4,10,12,14, 21,36]. Although the frame ensures a high precision, it is unsuitable for the thin skulls of young children and its use usually mandates general anesthesia [3,33]. Frameless systems are also used for pediatric radiosurgery, often aided by customized head holders for immobilization. Many centers, however, are reluctant to use frameless systems for single-shot radiosurgery, which requires uncompromising precision and accuracy [22]. A robotically controlled radiosurgical system (Cyberknife, Accuray, Inc., Sunnyvale, California) has recently ß 2004 Wiley-Liss, Inc. DOI 10.1002/pbc.20267

been developed, which consists of a linear accelerator mounted on a robotic arm [1,29]. Because of the use of a large number of beams and because the position of the robot is updated with real-time radiographs obtained during treatment, the system achieves precision and accuracy rivaling that of frame-based systems but without the requirement of a rigid frame [1,6,25]. We hypothesized that these advantages might make the Cyberknife ideal for pediatric radiosurgery, since the lack of requirement for a frame allows treatment of infants and young children and might obviate the need for general anesthesia in older children. We have reported our preliminary experience ——————

1

Baylor University Medical Center, Dallas, Texas

2

Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas

3

Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas

4

Children’s Medical Center, Dallas, Texas

5

Arlington Cancer Center, Arlington, Texas

*Correspondence to: Cole A. Giller, Baylor University Medical Center, HTPN, 8080 N. Central Expressway, Suite 1650, Dallas, TX 75206. E-mail: [email protected] Received 28 July 2004; Accepted 8 October 2004