Lin Alexander J, Zhang Juying, Cho-Lim Jennie, Inouye Warren, Lee Steve P
Department of Radiation Oncology, VA Long Beach Healthcare System, Long Beach, CA; Department of Radiation Oncology, University of California, Irvine, CA.
Department of Radiation Oncology, VA Long Beach Healthcare System, Long Beach, CA; Department of Radiation Oncology, University of California, Los Angeles, CA.
Med Dosim. 2019;44(1):56-60. doi: 10.1016/j.meddos.2018.02.001. Epub 2018 Mar 23.
We performed a case-control study to characterize the dose-volume relationship and other variables leading to hypothyroidism after head and neck (H&N) cancer radiation therapy (RT) in a homogenous Veterans Affairs (VA) population. All records of patients receiving RT for various H&N cancers at a single VA medical center between 2007 and 2013 (n = 143) were screened for post-RT thyroid stimulating hormone (TSH) levels (n = 77). The thyroid gland was contoured on each slice of the planning computed tomography scan when available (hypothyroid: n = 18; euthyroid > 2 years: n = 16), and dose-volume histograms based on physical dose and biologically equivalent dose (BED) were compared systematically to find the significant dose-volume thresholds that distinguish the patients who developed clinical hypothyroidism. Dosimetric and clinical variables were considered in univariate and multivariate analysis. Preirradiation prevalence of hypothyroidism was 8 of 143 (5.6%). After RT, 36 of 77 (47%) screened patients had abnormally high TSH, of which 22 of 36 (61%) had clinical hypothyroidism after 1.29 ± 0.99 years. The median follow-up durations were 3.3 years and 4.7 years for euthyroid and hypothyroid patients, respectively. Compared with the euthyroid cohort (n = 41), these hypothyroid patients displayed no significant difference in age, gender, primary tumor site, thyroid volume, hypertension, diabetes, or use of chemotherapy, surgery, or intensity-modulated radiation therapy (IMRT). They were more likely to have had stage 3 or 4 cancer than euthyroid patients (86.5% vs 73.2%, p = 0.01). The odds ratios of hypothyroidism for stage 3 + 4 cancers and V50Gy < 75% were 5.0 and 0.2, respectively (p < 0.05). Equivalent BED threshold of V75Gy < 75% gave an odds ratio of 0.156 for developing hypothyroidism (p = 0.02). The prevalence of post-RT clinical hypothyroidism was relatively high for patients with H&N cancers and warrants routine surveillance, especially in those with higher stage malignancy. V50Gy < 75% may be a useful guideline to avoid hypothyroidism. We also show BED data which could be used for unconventionally fractionated schemes, and V75Gy < 75% may be a useful guideline.
我们开展了一项病例对照研究，以确定在同质化的退伍军人事务部（VA）人群中，头颈部（H&N）癌放疗（RT）后导致甲状腺功能减退的剂量-体积关系及其他变量。对2007年至2013年间在单一VA医疗中心接受各种H&N癌放疗的患者的所有记录（n = 143）进行筛查，以获取放疗后促甲状腺激素（TSH）水平（n = 77）。如有可能，在计划计算机断层扫描的每一层上勾勒出甲状腺轮廓（甲状腺功能减退：n = 18；甲状腺功能正常>2年：n = 16），并系统比较基于物理剂量和生物等效剂量（BED）的剂量-体积直方图，以找出区分发生临床甲状腺功能减退患者的显著剂量-体积阈值。在单因素和多因素分析中考虑剂量学和临床变量。放疗前甲状腺功能减退的患病率为143例中的8例（5.6%）。放疗后，77例接受筛查的患者中有36例（47%）TSH异常升高，其中36例中的22例（61%）在1.29±0.99年后出现临床甲状腺功能减退。甲状腺功能正常和甲状腺功能减退患者的中位随访时间分别为3.3年和4.7年。与甲状腺功能正常队列（n = 41）相比，这些甲状腺功能减退患者在年龄、性别、原发肿瘤部位、甲状腺体积、高血压、糖尿病或化疗、手术或调强放疗（IMRT）的使用方面无显著差异。与甲状腺功能正常的患者相比，他们患3期或4期癌症的可能性更大（86.5%对73.2%，p = 0.01）。3 + 4期癌症和V50Gy < 75%的甲状腺功能减退优势比分别为5.0和0.2（p < 0.05）。V75Gy < 75%的等效BED阈值导致发生甲状腺功能减退的优势比为0.156（p = 0.02）。H&N癌患者放疗后临床甲状腺功能减退的患病率相对较高，需要进行常规监测，尤其是在那些患有更高分期恶性肿瘤的患者中。V50Gy < 75%可能是避免甲状腺功能减退的有用指导原则。我们还展示了可用于非常规分割方案的BED数据，V75Gy < 75%可能是一个有用的指导原则。
