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Dose-Volume Analysis of Radiation-Induced Optic Neuropathy After Single-Fraction Stereotactic Radiosurgery

Pollock, Bruce E. MD*,‡; Link, Michael J. MD*,§; Leavitt, Jacqueline A. MD; Stafford, Scott L. MD

Neurosurgery:
doi: 10.1227/NEU.0000000000000457
Research-Human-Clinical Studies
Abstract

BACKGROUND: The risk of radiation-induced optic neuropathy (RION) is the primary limitation of single-fraction stereotactic radiosurgery (SRS) for many patients with parasellar lesions.

OBJECTIVE: To define the normal tissue complication probability of the anterior visual pathways (AVPs) after single-fraction SRS.

METHODS: Retrospective review comparing visual function before and after SRS in 133 patients (266 sides) with pituitary adenomas having SRS between October 2007 and July 2012. Patients with prior radiation therapy or SRS were excluded. The median follow-up after SRS was 32 months.

RESULTS: The median maximum point dose to the AVP was 9.2 Gy (interquartile range [IQR], 6.9-10.8). One hundred seventy-four sides (65%) received >8 Gy: the median 8-Gy volume was 15.8 mm3 (IQR, 3.7-36.2). Ninety-four sides (35%) received >10 Gy; the median 10-Gy volume was 1.6 mm3 (IQR, 0.5-5.3). Twenty-nine sides (11%) received >12 Gy; the median 12-Gy volume was 0.1 mm3 (IQR, 0.1-0.6). No patient had a RION after SRS. The chances of developing a RION at the 8-Gy, 10-Gy, and 12-Gy volumes (95% confidence interval) in this series were 0% to 2.6%, 0% to 4.7%, and 0% to 13.9%, respectively.

CONCLUSION: The AVP in patients without prior radiation treatments can safely receive radiation doses up to 12 Gy with a low risk of RION. Although additional studies are needed to better delineate the normal tissue complication probability of the AVP, adherence to the AVP radiation tolerance guidelines developed 20 years ago (8 Gy) limits the applicability and potentially the effectiveness of single-fraction SRS for patients with lesions in the parasellar region.

ABBREVIATIONS: AVP, anterior visual pathway

CI, confidence interval

EBRT, external beam radiation therapy

IQR, interquartile range

RION, radiation-induced optic neuropathy

SRS, stereotactic radiosurgery

Author Information

*Department of Neurological Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota;

Department of Radiation Oncology, Mayo Clinic College of Medicine, Rochester, Minnesota;

§Department of Otorhinolaryngology-Head and Neck Surgery, Mayo Clinic College of Medicine, Rochester, Minnesota;

Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, Minnesota

Correspondence: Bruce E. Pollock, MD, Department of Neurological Surgery, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail: pollock.bruce@mayo.edu

Received February 21, 2014

Accepted May 02, 2014

Copyright © by the Congress of Neurological Surgeons