Nanda Tavish, Wu Cheng-Chia, Campbell Ashley A, Bathras Ryan M, Jani Ashish, Kazim Michael, Wang Tony J C
Columbia University College of Physicians and Surgeons, New York, NY, USA; Harkness Eye Institute, Columbia University Medical Center, New York, NY, USA; Department of Radiation Oncology, Columbia University Medical Center, New York, NY, USA.
Department of Radiation Oncology, Columbia University Medical Center, New York, NY, USA.
Med Dosim. 2017;42(4):357-362. doi: 10.1016/j.meddos.2017.07.007. Epub 2017 Aug 4.
With improvements in systemic therapy, patients with cancer treated with whole-brain radiotherapy (WBRT) are living long enough to develop late toxicities, including dry eye syndrome. In general practice, dose to the lacrimal gland (LG) is not constrained (maximum constraint <40 Gy) in WBRT. The purpose of this study was to measure dose to the LG in WBRT and determine methods for reducing radiation exposure. We conducted a retrospective review of 70 3-dimensional (3D) conformal plans; thirty-six plans with a radiation prescription of 30 Gy in 10 fractions and 34 plans with a prescription of 37.5 Gy in 15 fractions. LGs were contoured in accordance with Freedman and Sidani (2015). Biological effective dose (BED)3 maximum constraints were calculated from 40 Gy and 20 Gy to be 32.17 Gy (30 Gy) and 36.70 Gy (37.5 Gy). Both regimens demonstrated supraorbital blocking by 3 methods: T1, bordering the supraorbital ridge; T2, no contact with supraorbital ridge; and T3, coverage of the supraorbital ridge. Mean dose for the plans with a 30-Gy prescription and the plans with a 37.5-Gy prescription was 27.5 Gy and 35.2 Gy, respectively (p ≤ 0.0001). BED3 maximum constraint (D) was violated 16 of 26 (61.5%) in T1 (average D: 32.2 Gy), 13 of 28 (46.4%) in T2 (average D: 32.1 Gy), and 5 of 18 (27.8%) in T3 (average D: 31.8 Gy) for the 30-Gy prescription. D was violated in 32 of 32 (100%) in T1 (average D: 40.1 Gy), 22 of 22 (100%) in T2 (average D: 40.3 Gy), and 14 of 14 (100%) in T3 (average D: 39.4) for the 37.5 Gy prescription. Average D for the 37.5-Gy prescription was highly significant in favor of T3 (p = 0.0098). Patients who receive WBRT may develop dry eye syndrome as a late toxicity. Constraints are commonly violated with a prescription of 37.5 Gy. Methods to reduce dose include T3 supraorbital blocking, an easily implementable change that may dramatically improve patient quality of life.
随着全身治疗的改善，接受全脑放疗（WBRT）的癌症患者存活时间足够长，从而出现包括干眼症综合征在内的晚期毒性反应。在一般临床实践中，WBRT对泪腺（LG）的剂量未作限制（最大限制<40 Gy）。本研究的目的是测量WBRT中LG的剂量，并确定减少辐射暴露的方法。我们对70个三维（3D）适形计划进行了回顾性分析；36个计划的放射处方为10次分割共30 Gy，34个计划的处方为15次分割共37.5 Gy。LG根据Freedman和Sidani（2015年）的方法进行轮廓勾画。生物等效剂量（BED）3的最大限制从40 Gy和20 Gy计算得出，分别为32.17 Gy（30 Gy）和36.70 Gy（37.5 Gy）。两种治疗方案均通过3种方法进行眶上遮挡：T1，毗邻眶上嵴；T2，不接触眶上嵴；T3，覆盖眶上嵴。30 Gy处方计划和37.5 Gy处方计划的平均剂量分别为27.5 Gy和35.2 Gy（p≤0.0001）。对于30 Gy处方，T1组26例中有16例（61.5%）违反了BED3最大限制（D）（平均D：32.2 Gy），T2组28例中有13例（46.4%）（平均D：32.1 Gy），T3组18例中有5例（27.8%）（平均D：31.8 Gy）。对于37.5 Gy处方，T1组32例全部（100%）违反D（平均D：40.1 Gy），T2组22例全部（100%）（平均D：40.3 Gy），T3组14例全部（100%）（平均D：39.4 Gy）。37.5 Gy处方的平均D在T3组明显更低（p = 0.0098）。接受WBRT的患者可能会出现干眼症综合征作为晚期毒性反应。37.5 Gy的处方通常会违反剂量限制。减少剂量的方法包括T3眶上遮挡，这是一种易于实施的改变，可能会显著改善患者的生活质量。
