Canine pituitary tumours are increasingly treated with stereotactic radiotherapy (SRT). Here, we report clinical outcomes in dogs treated with single‐fraction SRT; we also explore technical aspects of SRT treatment planning. A single‐institution retrospective study was performed, including any dog with a pituitary mass (PM) that was treated using a standardized single‐fraction (16 Gy) SRT protocol between 2014 and 2017. Via medical records review, 13 cases were identified. Nine dogs neurologically improved after SRT. Four dogs experienced MRI‐documented tumour volume reduction. Nine dogs experienced neurologic decline in 1.5 to 18 months after SRT and were euthanized. The median overall survival time was 357 days, with 15% alive 18 months after SRT. To better understand whether SRT target delineation is predictably altered by use of magnetic resonance imaging (MRI) in addition to computed tomography (CT), two radiation oncologists (RO) retrospectively re‐evaluated all imaging studies used for SRT planning in these 13 cases. Gross tumour volume (GTV) was contoured on co‐registered CT and MRIs for each case. In seven cases, CT alone was deemed inadequate for GTV contouring by at least one RO. T1 post‐contrast MRI was considered the ideal image for GTV contouring in 11 cases. Contouring on MRI yielded larger GTV than CT for 11 cases. Inter‐observer variability existed in each case and was greater for MRI. In summary, use of co‐registered CT and MRI images is generally considered advantageous for PM delineation when using SRT. Notably, survival times reported herein are shorter than what has previously been reported for PM treated with finely fractionated full‐course RT protocols.

中文翻译：

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使用 CT 和 MRI 对 13 只狗进行垂体肿块统一立体定向放射治疗方案（16 Gy 单次放射治疗）的治疗结果和靶区描绘：（2014-2017）

犬垂体肿瘤越来越多地采用立体定向放射疗法 (SRT) 进行治疗。在这里，我们报告了接受单次 SRT 治疗的犬的临床结果；我们还探讨了 SRT 治疗计划的技术方面。进行了一项单机构回顾性研究，包括在 2014 年至 2017 年期间使用标准化单次 (16 Gy) SRT 方案治疗的任何垂体肿块 (PM) 犬。通过医疗记录审查，确定了 13 例病例。SRT 后 9 只狗的神经系统得到改善。四只狗经历了 MRI 记录的肿瘤体积减少。9 只狗在 SRT 后 1.5 至 18 个月内出现神经功能衰退并被实施安乐死。中位总生存时间为 357 天，SRT 后 18 个月存活率为 15%。为了更好地了解除了计算机断层扫描 (CT) 之外，使用磁共振成像 (MRI) 是否可预测地改变 SRT 靶区描绘，两名放射肿瘤学家 (RO) 回顾性地重新评估了这 13 例用于 SRT 计划的所有成像研究。每个病例的总肿瘤体积 (GTV) 在共同配准的 CT 和 MRI 上绘制轮廓。在七种情况下，至少有一个 RO 认为仅 CT 不足以进行 GTV 轮廓绘制。T1 增强后 MRI 被认为是 11 例 GTV 轮廓的理想图像。11 例 MRI 上的轮廓产生比 CT 更大的 GTV。在每种情况下都存在观察者间的变异性，并且在 MRI 中更大。总之，当使用 SRT 时，使用共同配准的 CT 和 MRI 图像通常被认为有利于 PM 描绘。尤其，