Invited Review—neuroimaging Response Assessment Criteria for Brain Tumors in Veterinary Patients

Abstract

The evaluation of therapeutic response using cross-sectional imaging techniques, particularly gadolinium-enhanced MRI, is an integral part of the clinical management of brain tumors in veterinary patients. Spontaneous canine brain tumors are increasingly recognized and utilized as a translational model for the study of human brain tumors. However, no standardized neuroimaging response assessment criteria have been formulated for use in veterinary clinical trials. Previous studies have found that the pathophysiologic features inherent to brain tumors and the surrounding brain complicate the use of the Response Evaluation Criteria in Solid Tumors (RECIST) assessment system. Objectives of this review are to describe strengths and limitations of published imaging-based brain tumor response criteria and propose a system for use in veterinary patients. The widely used human Macdonald and Response Assessment in Neuro-oncology (RANO) criteria are reviewed and described as to how they can be applied to veterinary brain tumors. Discussion points will include current challenges associated with the interpretation of brain tumor therapeutic responses such as imaging pseudophenomena and treatment-induced necrosis, and how advancements in perfusion imaging, positron emission tomography, and magnetic resonance spectroscopy have shown promise in differentiating tumor progression from therapy-induced changes. Finally, although objective endpoints such as MR-imaging and survival estimates will likely continue to comprise the foundations for outcome measures in veterinary brain tumor clinical trials, we propose that in order to provide a more relevant therapeutic response metric for veterinary patients, composite response systems should be formulated and validated that combine imaging and clinical assessment criteria.

Maximizing Local Access to Therapeutic Deliveries in Glioblastoma. Part V: Clinically Relevant Model for Testing New Therapeutic Approaches

“…Incorporating therapeutic plans developed from patient-specific, segmented medical images imported into finite element analysis modeling software, we have confirmed the ability of IRE and H-FIRE to safely and precisely ablate normal and neoplastic canine brain tissues with a submillimeter line of demarcation between ablated and non-treated tissues (79,86,89). IRE treatment of canine gliomas resulted in significant objective tumor responses in 4/5 dogs with quantifiable target lesions (Figure 3), and these radiographic responses were accompanied by improvements in Karnofsky (72,86). Similarly, using a treat and resect treatment paradigm, we have confirmed the ability of H-FIRE to safely and precisely ablate clinically relevant volumes of canine brain tumors without the induction of muscular contractions during pulse delivery (Figure 4).…”

“…Efficacy is determined by characterizing objective tumor responses using RANO and volumetric criteria modified for use in canine patients (72). Using this approach, we have achieved robust and clinically relevant volumes of infusate distribution in unresected canine MGs (Figure 2).…”

Comparison of visual metric and planimetry methods for brain tumor measurement in dogs

“…15 Recently, criteria were proposed for assessment of veterinary neuro-oncology patients, referred to as response assessment in veterinary neuro-oncology. 16 Criteria for human and veterinary assessment are largely based on diameter measurements in 2 or 3 dimensions.…”

New Treatment Modalities for Brain Tumors in Dogs and Cats

“…[1][2][3][4] MRI has also served as a fundamental platform for the development of technologies and procedures that have contributed to improvements in the management of brain tumors, including image-guided neuronavigation, functional neuroimaging, surgical and radiotherapeutic planning, and objective therapeutic response assessment. [5][6][7][8][9] Despite this progress, definitive antemortem diagnosis of brain tumors in animals remains uncommon, and few data exist in veterinary medicine regarding the influence of treatment on clinical outcomes of animals with brain tumors. Primary brain tumors, in particular the malignant variants, remain a source of significant morbidity and mortality in small animals and humans.…”