Definitive-intent uniform megavoltage fractioned radiotherapy protocol for presumed canine intracranial gliomas: retrospective analysis of survival and prognostic factors in 38 cases (2013–2019)

Abstract

Background Radiotherapy (RT) is currently considered the treatment of choice for presumed canine intracranial gliomas. However, variable therapeutic responses are described, due to heterogeneous populations and different radiation methods or protocols. Only one study dedicated to intracranial suspected glioma highlighted prognostic criteria. Determination or confirmation of specific clinical and imaging prognostic factors may guide the therapeutic management of these tumours. The objectives were to provide data on long-term clinical outcome (including quality of life, QoL) and to determine specific prognostic factors associated with survival time. We report a single-institution retrospective study, including all dogs with suspected symptomatic primary solitary intracranial glioma, treated with a complete uniform fractionated megavoltage radiation protocol of 15x3Gy over 5 weeks, between January 2013 and February 2019. Thirty-eight client-owned dogs were included. Medical records were retrospectively evaluated for median overall survival time (MST), clinical and imaging responses. Prognostic factors on survival were researched in terms of signalment, clinical presentation, tumour imaging characteristics and response following RT. Finally, the RT’s impact on the dogs’ clinical signs and Qol were evaluated by the owners. Results The disease-specific MST was 698 days (95% CI: 598–1135). Survival at 1 and 2 years were respectively 74.2 ± 7.4% and 49.0 ± 9.8%. Initial clinical signs were related to survival, as well as tumour characteristics such as cystic-pattern, mass effect and Tumour/Brain volume ratio. No significant adverse effect or radiotoxicity was observed. Conclusions RT appears as a safe and effective treatment for canine intracranial gliomas, allowing long-term tumour control, improvement of life’s quality and management of associated clinical signs. The initial clinical signs and MRI characteristics (Tumour/Brain volume ratio, cyst-like lesion and mass effect) may help predict the prognosis.

Clinical and Magnetic Resonance Imaging (MRI) Features, Tumour Localisation, and Survival of Dogs with Presumptive Brain Gliomas

“…In our study, 80% of dogs belonged to one of these breeds. Our population differed from others in that two-thirds of the dogs were French Bulldogs, while in other reports these percentages ranged between 7% and 52% [5][6][7]24]. This probably not only reflects the popularity of this breed in our geographical area but also highlights a higher predisposition.…”

“…Previous studies have found a genetic predisposition to develop brain gliomas in Bulldogs, Boxers, and Boston Terriers, with percentages ranging from 48% to 78% [4][5][6][7][8]10,12,24]. In our study, 80% of dogs belonged to one of these breeds.…”

“…Brachycephalic dogs have shown a predisposition [4][5][6][7][8], and males are reported in many studies to be overrepresented [7,8]. Most brain gliomas are rostrotentorial, and neurological signs are variable, with epileptic seizures (ES) being the most frequently described clinical sign.…”

“…Sci. 2022, 9, 257 2 of 18 The reported overall survival times (OS) in canine gliomas are mainly related to the chosen treatment [6,7,11,12]. Described OS for dogs with brain gliomas that receive palliative treatment are short, ranging from 26 to 94 days [7,[12][13][14].…”

Temozolomide is additive with cytotoxic effect of irradiation in canine glioma cell lines

“…Similar to human glioblastoma, canine glial tumors are associated with high treatment resistance and guarded overall outcome. Single‐modality radiation therapy or surgery often represents the most promising strategy with median survival times of 8–23 months (Debreuque et al., 2020 ; Hubbard et al., 2018 ; Schwarz et al., 2018 ). Other than in human medicine and rodent models using human xenografts, possible benefit of combined treatment has not been described.…”