Stereotactic radiotherapy outcomes for intraventricular brain tumours in 11 dogs.

Published radiotherapy data for canine intraventricular tumours are limited. In this retrospective, longitudinal study (9/2011-2018), 11 dogs with intraventricular masses were treated with stereotactic radiotherapy (SRT). Pathologic diagnosis was available from surgery or necropsy in 6/11 cases, revealing choroid plexus papilloma (3) or carcinoma (2), and ependymoma (1). The remainder were magnetic resonance imaging (MRI)-diagnosed as suspected choroid tumours or ependymomas. Tumours were located in the third or lateral ventricle (8), fourth ventricle (2), and cerebellopontine angle (1). Surgery was performed in three dogs prior to radiotherapy, and all showed gross residual/recurrent disease at treatment. Dogs received 8 Gray × 3 fractions (7), or 15 Gray × 1 fraction (4). Ten dogs were deceased at analysis, and one was living. The estimated median overall survival time (OS) from first SRT treatment was 16.9 months (515 days, 95% CI 33-1593 days). The survival time for two pathology-diagnosed carcinoma dogs were 24 and 133 days, respectively, and survival time for dogs with moderate to marked ventriculomegaly (4/11) ranged from 24 to 113 days. A total of 10/11 showed clinical improvement per owner or clinician, but two had short-lived benefits and were euthanized within 6 weeks of SRT. Limited conclusions on radiation-specific complications are possible due to the small dataset and limited follow-up imaging. This study provides preliminary evidence that radiotherapy outcomes are variable with intraventricular tumours, and some long-term survivors are noted.

Conventional fractionated radiotherapy outcomes for young dogs with nephroblastoma of the spinal cord: 5 cases.

Published radiotherapy results for spinal nephroblastomas in dogs are limited. In this retrospective longitudinal study (1/2007-1/2022), five dogs with a median age of 2.8 years received post-operative 3D conformal, conventional fractionated radiotherapy (CFRT) with 2-4 fields (parallel-opposed with or without two hinge-angle fields), for an incompletely resected nephroblastoma. Clinical findings prior to surgery included one or more of the following: pelvic limb paresis (5), faecal incontinence (2), flaccid tail (1), non-ambulatory (2) and deep pain loss (1). All masses were located between T11 and L3 and surgically removed via hemilaminectomy. Dogs received 45-50 Gray (Gy) in 18-20 fractions, and no dogs received chemotherapy post-radiation. At analysis, all dogs were deceased, with none lost to follow-up. The median overall survival (OS) from first treatment to death of any cause was 3.4 years (1234 days; 95% CI 68 days-upper limit not reached; range: 68-3607 days). The median planning target volume was 51.3 cc, with a median PTV dose of 51.4 Gy and median D98 = 48.3 Gy. Late complications or recurrence was difficult to fully determine in this small dataset; however, some degree of ataxia persisted throughout life in all dogs. This study provides preliminary evidence that post-operative radiotherapy may result in prolonged survival times dogs with spinal nephroblastomas.

Pre-clinical and clinical evaluation of the HYPERSCINT plastic scintillation dosimetry research platform for in vivo dosimetry during radiotherapy.

PURPOSE: The purpose of this work is to evaluate the Hyperscint-RP100 scintillation dosimetry research platform (Hyperscint-RP100, Medscint Inc., Quebec, QC, Canada) designed for clinical quality assurance (QA) for use in in vivo dosimetry measurements. METHODS: The pre-clinical evaluation of the scintillator was performed using a Varian TrueBeam linear accelerator. Dependency on field size, depth, dose, dose rate, and temperature were evaluated in a water tank and compared to calibration data from commissioning and annual QA. Angularity was evaluated with a 3D printed phantom. The clinical evaluation was first performed in two cadaver dogs, and then in three companion animal dogs receiving radiation therapy for nasal tumors. A treatment planning CT scan was performed for cadavers and clinical patients. Prior to treatment, the probe was inserted into the radiation field. Radiation was then delivered and measured with the scintillator. For cadavers, the treatment was repeated after making an intentional shift in patient position to simulate a treatment error. RESULTS: In the preclinical measurements the dose differed from annual measurements as follows: field size -0.77 to 0.43%, depth dose -0.36 to 1.14%, dose -0.54 to 2.93%, dose rate 0.3 to 3.6%, and angularity -1.18 to 0.01%. Temperature dependency required a correction factor of 0.11%/°C. In the two cadavers, the dose differed by -1.17 to 0.91%. The device correctly detected the treatment error when the heads were intentionally laterally shifted. In three canine clinical patients treated in multiple fractions, the detected dose ranged from 98.33 to 103.15%. CONCLUSION: Results of this new device are promising although more work is necessary to fully validate it for clinical dosimetry.

Cats and chemotherapy: treat as 'small dogs' at your peril.

PRACTICAL RELEVANCE: To safely and effectively treat cats with cancer it is important to understand the drugs being used and some species-specific concerns in relation to chemotherapy. CLINICAL CHALLENGES: While many of the same principles in treating cats with chemotherapy and targeted agents hold true as for other species, including dogs, cats display altered metabolism of drugs and species-specific toxicities that can present particular challenges for veterinarians. AUDIENCE: This article is aimed at practitioners who treat feline cancer or who help manage cats undergoing cancer therapy. EVIDENCE BASE: The article reviews the known literature regarding species differences between dogs and cats relating to the use of chemotherapy and targeted therapies. For many of the drugs mentioned there are limited studies and caution must be exercised when using drugs that have a low therapeutic index.