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.

Canine presumed glial brain tumours treated with radiotherapy: Is there an inferior outcome in tumours contacting the subventricular zone?

“…5,6 One group, however, recently described cystic tumours of presumed glial origin to have shorter OS. 4 We found an increased risk for tumour progression in larger tumours.…”

“…This was in line with findings in dogs with glioma treated with radiation therapy, where the risk of death increased with relatively larger tumours. 4 The correlation described in Lim et al that tumour location relative to the SVZ predicts the pattern of progression and outcome focused on glioblastoma multiforme, while in our study histopathology is lacking and only imaging was available to characterize the brain tumours. The tumours described herein most likely represent a heterogenous glioma population.…”

“…MR features are commonly the only access to information on canine intracranial tumours treated with radiation therapy, as pretreatment histopathologic evaluation is uncommon. [4][5][6][34][35][36] MRI is the preferred modality for the evaluation of intracranial disease with a 70% accuracy of predicting the type of primary brain tumours. [37][38][39] While MR features provide a multitude of valuable information, no features allow to reliably differentiate tumours on a cellular level, such as astrocytoma from oligodendroglioma or provide a tumour grade.…”

“…Of these 10 cases, only three dogs experienced additional local progression. MR features are commonly the only access to information on canine intracranial tumours treated with radiation therapy, as pretreatment histopathologic evaluation is uncommon 4–6,34–36 . MRI is the preferred modality for the evaluation of intracranial disease with a 70% accuracy of predicting the type of primary brain tumours 37–39 .…”

“…Treatments for intracranial tumours in dogs have received a constant trickle of attention in the last decades, without massive improvement in outcome 1–3 . For glial tumours treated with radiation therapy, outcome is described with a rather broad range of median overall survival times between 8 and 23 months 4–6 . Median survival times after surgery range from 2 to 6 months, 7,8 with more promising outcomes of 7–28 months 9 when experimental unspecified therapy (chemo‐, immuno‐, gene‐therapy) was added.…”