BACKGROUND Dogs with sinonasal tumor can develop keratoconjunctivitis sicca (KCS) after radiation therapy (RT). In humans, the incidence of xerophtalmia is associated with the mean radiation dose received by the ipsilateral lacrimal gland (LG). HYPOTHESIS/OBJECTIVES The eyes receiving a higher mean LG dose are more likely to develop KCS. The aim of the study was to determine a starting threshold dose to use as dose constraint for intensity-modulated radiation therapy (IMRT). ANIMALS Dogs with nasal tumors treated with RT between August 2013 and December 2016. METHODS Case control retrospective study of dogs with sinonasal tumor treated with 42 Gray (Gy) in 10 fractions using IMRT. Dogs were included if development of KCS after RT was documented (cases) or adequate follow-up information with Schirmer tear test (STT) result for ≥6 months after RT was available (controls). Lacrimal glands were contoured and dose distribution was calculated using the original treatment plan to determine prescribed doses to LGs. RESULTS Twenty-five dogs were treated with RT and 5 dogs (20%) developed KCS. Fifteen dogs met the inclusion criteria including 5 unilateral KCS and 10 control dogs, resulting in 5 KCS eyes and 25 control eyes. KCS developed at a median of 111 days (84-122) after 1st RT. The mean LG dose reached using a 4.2 Gy per fraction was 33.08 Gy (range: 23.75-42.33) for KCS eyes and 10.33 Gy (1.8-24.77) for control eyes (P < .001). The minimum LG mean dose for developing KCS was 23.75 Gy. No eyes that received a mean LG dose <20 Gy developed KCS versus 5/7 (71%) developed with >20 Gy. CONCLUSION AND CLINICAL IMPORTANCE Contouring and applying a dose constraint on LGs should be performed when using IMRT in dogs with sinonasal tumors to reduce the risk of KCS.

中文翻译：

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放射疗法治疗鼻窦肿瘤狗的泪腺剂量与干燥性角结膜炎之间的临床剂量关系。

背景技术鼻窦肿瘤的狗可以在放射治疗（RT）后发展为干燥性角膜结膜炎（KCS）。在人类中，干燥性干燥症的发生与同侧泪腺（LG）接收到的平均辐射剂量有关。假设/目的接受较高平均LG剂量的眼睛更有可能患KCS。该研究的目的是确定起始阈值剂量，以用作强度调制放射治疗（IMRT）的剂量限制。动物在2013年8月至2016年12月之间，接受RT治疗的鼻肿瘤狗。方法病例对照研究回顾了使用IMRT对42份Gy（Gy）治疗的鼻窦肿瘤狗进行了10次治疗。如果记载了放疗后KCS的发展（病例），或在施行放疗后≥6个月具有Schirmer撕裂试验（STT）结果的足够的随访信息（对照），则将狗包括在内。轮廓泪腺，并使用原始治疗计划计算剂量分布，以确定LG的处方剂量。结果25只狗接受了RT治疗，而5只狗（占20％）发展为KCS。符合入选标准的15只犬包括5只单侧KCS和10只对照犬，导致5只KCS眼和25只对照眼。第一次RT后，KCS的中位数为111天（84-122）。使用每级4.2 Gy的LG平均剂量对于KCS眼睛为33.08 Gy（范围：23.75-42.33），对于对照眼为10.33 Gy（1.8-24.77）（P <.001）。发育KCS的最低LG平均剂量为23.75 Gy。接受平均LG剂量<20 Gy的眼睛没有发展为KCS，而超过20 Gy的为5/7（71％）。结论和临床意义在患有鼻窦肿瘤的狗中使用IMRT时，应当对LGs进行轮廓和剂量限制，以降低KCS风险。