Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
Department of Medical Physics, Grand River Regional Cancer Centre, Kitchener, Ontario, Canada.
Vet Comp Oncol. 2022 Sep;20(3):559-567. doi: 10.1111/vco.12807. Epub 2022 Mar 7.
Radiation therapy (RT) is being utilized more commonly for rabbit thymomas due to high perioperative mortality rates with surgery. Median overall survival times reported for rabbit thymomas treated with a variety of RT protocols and techniques range from 6 months to greater than 2 years. As thymomas are radiation-responsive tumours and may shrink rapidly after RT, adaptive radiotherapy (ART) is often warranted. The purpose of this single-institution retrospective case series was to investigate the tumour volume reduction during RT, the frequency of replanning during RT, and survival time in rabbit thymomas treated using intensity-modulated/image-guided radiation therapy (IMRT/IGRT) and a weekly hypofractionated protocol delivering a total dose of 30 Gy. Ten rabbits met the inclusion criteria from October 2014 to October 2019. The median progression-free survival was 561 days and the median overall survival was 634 days (range: 322-1118 days). The tumour volume gradually decreased with each RT fraction. On post-hoc analysis, only the first RT fraction was associated with a significant GTV reduction (of more than 50% on average, p < .001). All subsequent RT fractions did not further reduce the GTV significantly (p > .06). Hypofractionated RT using a weekly protocol of 5 fractions of 6 Gy is a reasonable option to treat rabbit thymomas and replanning should be anticipated. The results of this study support the use of RT to rapidly relieve thymoma-induced dyspnoea in rabbits.
放射治疗（RT）在兔胸腺瘤中的应用越来越普遍，因为手术的围手术期死亡率很高。用各种 RT 方案和技术治疗的兔胸腺瘤的中位总生存时间报告从 6 个月到 2 年以上不等。由于胸腺瘤是辐射敏感的肿瘤，并且在 RT 后可能迅速缩小，因此通常需要适应性放射治疗（ART）。本单机构回顾性病例系列研究的目的是调查兔胸腺瘤在 RT 期间的肿瘤体积缩小、RT 期间重新计划的频率以及使用调强/图像引导放射治疗（IMRT/IGRT）和每周分次方案治疗的生存时间，该方案总剂量为 30Gy。2014 年 10 月至 2019 年 10 月，有 10 只兔子符合纳入标准。无进展生存期的中位数为 561 天，总生存期的中位数为 634 天（范围：322-1118 天）。肿瘤体积随每次 RT 逐渐缩小。事后分析表明，只有第一次 RT 与 GTV 显著减少有关（平均减少超过 50%，p<.001）。所有后续 RT 剂量均未进一步显著减少 GTV（p>.06）。每周 5 次、每次 6Gy 的分次 RT 是治疗兔胸腺瘤的合理选择，应预期进行重新计划。本研究结果支持使用 RT 迅速缓解兔胸腺肿瘤引起的呼吸困难。
