2012年10月28-31日，第54届美国放射肿瘤学会（ASTRO）年会在美国波士顿举行。来自世界各地的放射肿瘤学领域的医生及相关人士共计11000多人参会。本届年会的主题是“通过创新改善患者治疗（Advancing Patient Care through Innovation）”。金宝搏网站登录技巧 对本届年会进行了专题报道（http://zt.cmt.com.cn/zt/astro2012/index.html），敬请关注！

　　会上，美国学者报告了一项研究：A New Use for an Old Treatment: Radiation Therapy and Alzheimer's Disease ，其摘要如下：

Purpose/Objective(s)
Alzheimer disease (AD) is the most common form of dementia in the United States and currently affects 1 in 8 older Americans. AD is characterized by extracellular beta-amyloid (Aβ) plaques and neurofibrillary tangles of Tau protein. Existing drugs for AD provide only short-term symptomatic relief without affecting disease progression, while the development of new drugs is overtly time consuming and costly. Therefore, we investigated an entirely novel strategy to treat AD pathologies using single dose and low-dose fractionated cranial X-irradiation. The aim of the current study is to define the role of dose intensity.

Materials/Methods
Two transgenic mouse models of AD, B6.Cg-Tg (APPswe,PSEN1dE9)85Dbo/J and B6;129-Psen1tm1MpmTg(APPSwe tauP301L)1Lfa/J (which express human Aβ, and human Aβ and tau transgenes, respectively) were X-irradiated (160 kVp Faxitron cabinet, 0.5 mm Cu and Al filters [HVL: 0.77 (mm CU)]) using a dose rate of 0.69 Gy/min. Animals were treated at 6 months of age when Aβ plaques are abundant in the cortex with smaller numbers evident in the hippocampus. Single doses of 5-15 Gy or fractionated treatments (1 Gy daily x 10 days, 2 Gy x 5 days) were given. Aβ plaques were assessed at 2-8 weeks post RT in histological sections, along with biomarkers of radiation injury and inflammation to evaluate the effects of dose intensity on AD pathology. Tau expression at 4 weeks post-RT was scored as percent hemi-brain involvement and tangle grade (using a qualitative 4-point scale).

Results
Both single dose and fractionated treatments were effective at reducing insoluble Aβ plaques. Overall, increasing the size of the single dose treatment (5 Gy, 10 Gy, and 15 Gy) produced a more effective response. The corresponding average reduction in Aβ plaques at 4 weeks post treatment was 29.3%, 45.7% and 56.9% respectively for the single dose treatments, while the fractionated schedules produced 50.6% (1 Gy x 10), and 72% (2 Gy x 5) reductions. Given the BED (α/β = 2) of the five regimens is 17.5 (5 Gy), 60 (10 Gy), 116 (15 Gy), 15 (1 Gy x 10), and 30 (2 Gy x 5), the effect is independent of dose intensity. However, assessment time post treatment is important. The reduction in plaques after a single dose of 10 Gy, at 2, 4 and 8 wks was 32.8% (±12.5), 45.7% (±11.8), and 54.2% (±19.3). In addition, RT was associated with a 38% mean reduction in Tau expression and 15% mean reduction in tangle grade in the tau transgenic model. The less intense fractionated schedules produced lower levels of neuronal cell death (p = 0.012).

Conclusions
These experiments indicate that low-dose fractionated external beam ionizing radiation produces a significant reduction in amyloid-β plaques and Tau-expression, pathologies linked with AD. The 2 Gy x 5 regimen was the most effective. These data suggest that radiation therapy could therefore be used a novel treatment of AD-associated pathologies.