CLINICAL STUDIES VISUAL FIELD PRESERVATION AFTER MULTISESSION CYBERKNIFE RADIOSURGERY FOR PERIOPTIC LESIONS John R. Adler, Jr., M.D. Departments of Neurosurgery and Radiation Oncology, Stanford University Medical School, Stanford, California Iris C. Gibbs, M.D. Department of Radiation Oncology, Stanford University Medical School, Stanford, California Putipun Puataweepong, M.D. Department of Neurosurgery, Stanford University Medical School, Stanford, California Steven D. Chang, M.D. Department of Neurosurgery, Stanford University Medical School, Stanford, California Reprint requests: John R. Adler, Jr., M.D., Department of Neurosurgery, Room R-205, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305. Email: jra@stanford.edu Received, December 15, 2005. Accepted, April 6, 2006. OBJECTIVE: The restricted radiation tolerance of the anterior visual pathways repre- sents a unique challenge for ablating adjacent lesions with single-session radiosurgery. Although preliminary studies have recently demonstrated that multisession radiosur- gery for selected perioptic tumors is both safe and effective, the number of patients in these clinical series was modest and the length of follow-up limited. The current retrospective study is intended to help address these shortcomings. METHODS: Forty-nine consecutive patients with meningioma (n = 27), pituitary adenoma (n = 19), craniopharyngioma (n = 2), or mixed germ cell tumor (n = 1) situated within 2 mm of a “short segment” of the optic apparatus underwent multi- session image-guided radiosurgery at Stanford University Medical Center. Thirty-nine of these patients had previous subtotal surgical resection, and six had previously been treated with conventional fractionated radiotherapy (6). CyberKnife radiosurgery was delivered in two to five sessions to an average tumor volume of 7.7 cm 3 and a cumulative average marginal dose of 20.3 Gy. Formal visual testing and clinical examinations were performed before treatment and at follow-up intervals beginning at 6 months. RESULTS: After a mean visual field follow-up of 49 months (range, 6–96 mo), vision was unchanged postradiosurgery in 38 patients, improved in eight (16%), and worse in three (6%). In each instance, visual deterioration was accompanied by tumor progression that ultimately resulted in patient death. However, one of these patients, who had a multiply recurrent adrenocorticotropic hormone-secreting pituitary ade- noma, initially experienced early visual loss without significant tumor progression after both a previous course of radiotherapy and three separate sessions of radiosurgery. After a mean magnetic resonance imaging follow-up period of 46 months, tumor volume was stable or smaller in all other cases. Two patients died of unrelated nonbrain causes. CONCLUSION: Multisession radiosurgery resulted in high rates of tumor control and preservation of visual function in this group of perioptic tumors. Ninety-four percent of patients retained or improved preradiosurgical vision. This intermediate-term experi- ence reinforces the findings from earlier studies that suggested that multisession radiosurgery can be a safe and effective alternative to either surgery or fractionated radiotherapy for selected lesions immediately adjacent to short segments of the optic apparatus. KEY WORDS: CyberKnife, Meningioma, Pituitary adenoma, Stereotactic radiosurgery Neurosurgery 59:244-254, 2006 DOI: 10.1227/01.NEU.0000223512.09115.3E www.neurosurgery-online.com S ingle-session radiosurgical ablation has become a gener- ally accepted technique for managing a spectrum of small cranial base and inaccessible brain lesions (3, 14, 19, 21, 22, 28, 30, 33, 37, 45, 48, 51–53, 55–57, 62–65, 68, 70, 71, 74, 75). Nevertheless, the proximity of the anterior visual path- ways (optic nerve and optic chiasm) poses a particular chal- lenge for ablating “perioptic” tumors; it is widely acknowl- edged that the unique radiation sensitivity of the normal optic apparatus precludes conventional radiosurgery when a lesion is within 2 mm of the anterior visual pathways (23, 25, 35, 36, 244 | VOLUME 59 | NUMBER 2 | AUGUST 2006 www.neurosurgery-online.com