Volumetric-modulated arc stereotactic radiotherapy for canine adrenocortical tumours with vascular invasion

To evaluate the feasibility and efficacy of hypofractionated stereotactic volumetric-modulated arc radiotherapy in treating canine adrenal tumours with vascular invasion.

A single-arm clinical study was performed. The dogs underwent total body computed tomography, brain and abdomen magnetic resonance imaging and endocrine assay. Adrenal masses were classified as cortisol-secreting adrenal tumour or non-secreting adrenal tumour. Radiotherapy treatments were delivered by hypofractionated stereotactic volumetric-modulated arc radiotherapy via a linear accelerator. The overall survival was estimated by the Kaplan-Meier method. The overall response and radio-toxicity effects were determined.

Nine dogs were enrolled. Three dogs were affected by cortisol-secreting adrenal tumours and the remaining dogs had non-secreting adrenal tumours. The prescribed doses ranged from 30 to 45 Gy in three or five consecutive daily fractions. The median overall survival time was 1030 days, and the overall mean reduction of the diameter and volume were ~32 and 30% respectively. The endocrine profile normalised in two dogs with cortisol-secreting adrenal tumours. Radio-toxicities were mild and self-limiting. Seven deaths were recorded during the follow-up period and two dogs were censored.

Hypofractionated stereotactic volumetric-modulated arc radiotherapy should be considered as a feasible and effective therapeutic option for adrenal tumours with vascular invasion.