Single fraction stereotactic radiation therapy (stereotactic radiosurgery) is a feasible method for treating intracranial meningiomas in dogs

Abstract

The aim of this retrospective, pilot study was to evaluate stereotactic radiosurgery as a method for treating intracranial meningiomas in dogs. Included dogs had an imaging diagnosis of presumed intracranial meningioma, were treated using a standardized stereotactic radiosurgery protocol, and had a follow-up time of >6 months after stereotactic radiosurgery. A single fraction of 16 Gy stereotactic radiosurgery was delivered to the tumor, with an internal simultaneously integrated boost to a total dose of 20-24 Gy to the central portion of the tumor. Thirty-two dogs were sampled. One dog was euthanized in the periprocedural period, and 10 of the remaining 31 dogs (31%) experienced an acute adverse event (defined as declining neurologic function due to tumor progression or treatment-associated complication within the first 6 months after stereotactic radiosurgery), three of which were fatal. Too few subjects (n = 6) had cross-sectional imaging after stereotactic radiosurgery to determine an objective response rate; however, 17/30 (57%) dogs assessed for response had a perceived clinical benefit from treatment. The overall median survival time was 519 days (95% confidence interval: 330-708 days); 64% and 24% of dogs were alive at 1 and 2 years after stereotactic radiosurgery, respectively. Dogs with infratentorial tumor location and high gradient indices had shorter survival. There were no factors identified which were predictive of acute adverse event. Survival times reported herein are similar to what has previously been reported for other stereotactic and traditional fractionated radiotherapy protocols. Findings therefore supported the use of stereotactic radiosurgery as an alternative method for treating dogs with presumed intracranial meningiomas.

Efficacy of frameless stereotactic radiotherapy for the treatment of presumptive canine intracranial gliomas: A retrospective analysis (2014‐2017)

“…The use of this hypo-fractionated form of RT, termed stereotactic radiation therapy (SRT), has been described for the treatment of various intracranial neoplasms. [14][15][16][17][18][19] The major concern with increasing dose per fraction when irradiating brain tumours relates to the potential to cause late delayed brain injury. Typically, the ideal target for SRT has well-defined margins, thus lending itself well to a rapid drop off of radiation dose outside of the defined target volume.…”

“…Consequently, little data exist on the efficacy and/or safety of SRT in dogs with glial tumours. 8,14,15,18 The objective of this retrospective study was to describe an SRT protocol of three fractions of 8 to 10 Gy for the treatment of canine patients with presumptive intracranial gliomas. Specifically, we aimed to demonstrate the delivery and to evaluate the efficacy and safety of such protocol.…”

Residual setup error in the canine intracranial region after megavoltage, kilovoltage, or cone‐beam computed tomographic image guidance for radiation therapy

“…When stereotactic radiation therapy (SRT) and stereotactic radiosurgery (SRS) are used to treat intracranial tumours, a small PTV expansion is desirable as normal tissues adjacent to the tumour are spared by avoidance, rather than fractionation. The PTV reported for canine patients with brain tumours treated with SRT and SRS in a variety of immobilization systems ranges from 0 to 3 mm . On‐board image guidance or portal imaging were used in these studies to minimize setup error.…”

Use of MRI increases interobserver agreement on gross tumor volume for imaging‐diagnosed canine intracranial meningioma

“…2 Highly conformal procedures utilizing intensity-modulated radiation therapy, such as stereotactic radiosurgery (SRS) and stereotactic radiation therapy (SRT), are increasingly used for canine intracranial meningioma. [4][5][6] Variability in GTV contours of a magnitude that could lead to errors in dose delivery greater than those due to variability in patient positioning has been reported for human brain tumor patients. 7,8 There are few investigations of interobserver variability in GTV delineation in veterinary patients.…”

“…15 A combination of CT and MRI is recommended for optimal target volume delineation for skull base meningiomas 13 and brain tumors 7 in human patients. Use of both CT and MRI to delineate GTV for meningiomas in canine patients is also reported [4][5][6]11,12 although CT imaging alone is also used. 6,11,12 The complementary data provided by CT and MRI for delineation of intracranial tumors and lack of information on the addition of MRI to CT imaging for treatment planning of canine meningiomas led to our second objective: to compare interobserver agreement on canine intracranial meningioma GTV delineation based on CT imaging alone versus fused CT-MRI.…”