Comparison of linear and volumetric criteria for the determination of therapeutic response in dogs with intracranial gliomas

Magnetic resonance and computed tomographic imaging characteristics and potential molecular mechanisms of feline meningioma associated calvarial hyperostosis

Meningiomas are the most common feline primary brain tumours, and calvarial hyperostosis (CH) is frequently documented in association with this neoplastic entity. The clinical significance of and mechanisms driving the formation of CH in cats with meningiomas are poorly understood, although tumour invasion into the skull and tumour production of cytokines and enzymes have been implicated as causes of CH in humans. This retrospective study investigated relationships between signalment, MRI or CT imaging features, histopathologic tumour characteristics, alkaline phosphatase (ALP) isoenzyme concentrations, tumour expression of matrix metalloproteinases (MMP)-2, MMP-9, and interleukin-6 (IL-6), and progression free survival times (PFS) following surgical treatment in 27 cats with meningiomas with (n = 15) or without (n = 12) evidence of CH. No significant differences in breed, age, sex, body weight, tumour grade, tumour volume, peritumoral edema burden, ALP isoenzyme concentrations, tumour Ki-67 labelling indices or MMP-2 or MMP-9 expression and activity, or PFS were noted between cats with or without CH. There was a trend towards higher serum (p = .06) and intratumoral (p = .07) concentrations of IL-6 in cats with CH, but these comparisons were not statistically significant. Histologic evidence of tumour invasion into bone was observed in 5/12 (42%) with CH and in no (0/6) cats without CH, although this was not statistically significant (p = .07). Tumour invasion into bone and tumour production of IL-6 may contribute to the formation of meningioma associated CH in cats, although larger studies are required to further substantiate these findings and determine their clinical relevance.

Chemotherapy for the treatment of intracranial glioma in dogs

Gliomas are the second most common primary brain tumor in dogs and although they are associated with a poor prognosis, limited data are available relating to the efficacy of standard therapeutic options such as surgery, radiation and chemotherapy. Additionally, canine glioma is gaining relevance as a naturally occurring animal model that recapitulates human disease with fidelity. There is an intense comparative research drive to test new therapeutic approaches in dogs and assess if results translate efficiently into human clinical trials to improve the poor outcomes associated with the current standard-of-care. However, the paucity of data and controversy around most appropriate treatment for intracranial gliomas in dogs make comparisons among modalities troublesome. To further inform therapeutic decision-making, client discussion, and future studies evaluating treatment responses, the outcomes of 127 dogs with intracranial glioma, either presumed (n = 49) or histologically confirmed (n = 78), that received chemotherapy as leading or adjuvant treatment are reviewed here. This review highlights the status of current chemotherapeutic approaches to intracranial gliomas in dogs, most notably temozolomide and lomustine; areas of novel treatment currently in development, and difficulties to consensuate and compare different study observations. Finally, suggestions are made to facilitate evidence-based research in the field of canine glioma therapeutics.

The T2-FLAIR mismatch sign as an imaging biomarker for oligodendrogliomas in dogs

BACKGROUND

In humans, the T2-weighted (T2W)-fluid-attenuated inversion recovery (FLAIR) mismatch sign (T2FMM) is a specific imaging biomarker for the isocitrate dehydrogenase 1 (IDH1)-mutated, 1p/19q non-codeleted low-grade astrocytomas (LGA). The T2FMM is characterized by a homogeneous hyperintense T2W signal and a hypointense signal with a hyperintense peripheral rim on FLAIR sequences. In gliomas in dogs, the T2FMM has not been described.

HYPOTHESES/OBJECTIVES

In dogs with focal intra-axial brain lesions, T2FMM will discriminate gliomas from other lesions. The T2FMM will be associated with the LGA phenotype and presence of microcysts on histopathology. Interobserver agreement for T2FMM magnetic resonance imaging (MRI) features will be high.

ANIMALS

One hundred eighty-six dogs with histopathologically diagnosed focal intra-axial lesions on brain MRI including oligodendrogliomas (n = 90), astrocytomas (n = 47), undefined gliomas (n = 9), cerebrovascular accidents (n = 33), and inflammatory lesions (n = 7).

METHODS

Two blinded raters evaluated the 186 MRI studies and identified cases with the T2FMM. Histopathologic and immunohistochemical slides of T2FMM cases were evaluated for morphologic features and IDH1-mutations and compared to cases without the T2FMM. Gene expression analyses were performed on a subset of oligodendrogliomas (n = 10) with and without T2FMM.

RESULTS

The T2FMM was identified in 14/186 (8%) of MRI studies, and all dogs with T2FMM had oligodendrogliomas (n = 12 low-grade [LGO], n = 2 high-grade [HGO]; P < .001). Microcystic change was significantly associated with the T2FMM (P < .00001). In oligodendrogliomas with T2FMM, IDH1-mutations or specific differentially expressed genes were not identified.

CONCLUSION AND CLINICAL IMPORTANCE

The T2FMM can be readily identified on routinely obtained MRI sequences. It is a specific biomarker for oligodendroglioma in dogs, and was significantly associated with non-enhancing LGO.

Dynamic contrast-enhanced computed tomography perfusion parameters of canine suspected brain tumors at baseline and during radiotherapy might be different depending on tumor location but not associated with survival

Introduction

Treatment of brain tumors in dogs can be associated with significant morbidity and reliable prognostic factors are lacking. Dynamic contrast-enhanced computed tomography (DCECT) can be used to assess tumor perfusion. The objectives of this study were to assess perfusion parameters and change in size of suspected brain tumors before and during radiotherapy (RT) depending on their location and find a potential correlation with survival.

Methods

Seventeen client-owned dogs with suspected brain tumors were prospectively recruited. All dogs had a baseline DCECT to assess mass size, blood volume (BV), blood flow (BF), and transit time (TT). Twelve dogs had a repeat DCECT after 12 Gy of megavoltage RT. Survival times were calculated.

Results

Intra-axial masses had lower BF (p = 0.005) and BV (p < 0.001) than extra-axial masses but not than pituitary masses. Pituitary masses had lower BF (p = 0.001) and BV (p = 0.004) than extra-axial masses. The volume of the mass was positively associated with TT (p = 0.001) but not with BF and BV. Intra-axial masses showed a more marked decrease in size than extra-axial and pituitary masses during RT (p = 0.022 for length, p = 0.05 for height). Extra-axial masses showed a greater decrease in BF (p = 0.011) and BV (p = 0.012) during RT than pituitary masses and intra-axial masses. Heavier dogs had a shorter survival time (p = 0.011). Perfusion parameters were not correlated with survival.

Conclusion

DCECT perfusion parameters and change in size of brain masses during RT might be different based on the location of the mass.