补硒在放射性临床治疗中的进展

Radiotherapy is an essential cancer treatment and contributes to the cure or palliation of many cancer patients. Approximately 50 % of patients who are diagnosed with cancer receive radiotherapy during the course of treatment. However, irradiation causes many side effects because of normal tissue injury . These short- and long-term side effects limit treatment tolerability and negatively affect quality of life of the patients , and thus it is important to reduce the side effects of radiotherapy .
Ionizing radiation results in the immediate generation of reactive oxygen species (ROS). ROS elevate oxidative stress in the cell and cause rapid protein modifications and damage to DNA, RNA, and cell membranes, which causes cell death and tissue damage.
In humans, there are 25 selenoproteins with selenocysteine at the active site. Glutathione peroxidases (GPxs) are selenoproteins and have strong activities in the reduction of ROS in most tissues. Selenium also exhibits roles in DNA-repair and cytokine control.
There is a good association between GPx activities and plasma selenium levels up to 70–100 μ g/L, which correlates with selenium intake and reflects short-term changes in the selenium state. Therefore,optimizing selenoprotein activities with supplementation has been considered beneficial in the course of treatment.
In our previous review, 16 clinical studies on the supplementation of selenium in radiotherapy between 1987 and 2012 were identified in PubMed. We concluded that selenium supplementation increased the blood selenium levels, improved quality of life, and prevented or reduced the side effects of radiotherapy, and did not reduce the effectiveness of radiotherapy or cause any toxicity. To establish guidelines for selenium supplementation in radiotherapy, we assessed the benefits and risks that were associated with selenium supplementation in radiotherapy through the recent advances in clinical studies.

放射治疗是一种重要的癌症治疗方法，有助于许多癌症患者的治愈或缓解。大约50%的被诊断为癌症的患者在治疗过程中接受放射治疗。然而，由于正常的组织损伤，辐射会引起许多副作用。这些短期和长期的副作用限制了治疗的耐受性，并对患者的生活质量产生负面影响，因此减少放疗的副作用非常重要。

放射治疗会立即产生大量氧自由基（ROS），ROS升高，细胞内的氧化应激增加，引起蛋白质的快速修饰和DNA、RNA、细胞膜的损伤，从而导致细胞死亡和组织损伤。

人体中含有25种含硒蛋白及硒代半胱氨酸作用于同一位点，谷胱甘肽过氧化物酶（GPxs）是一种硒蛋白，在大多数组织中具有很强的还原活性。硒还表现出DNA修复和细胞因子控制的作用。

GPx活性与血浆硒水平（高达70–100μg/L）之间存在良好的相关性，与硒摄入量相关，并反映硒状态的短期变化。因此，在治疗过程中，通过补充硒来优化硒蛋白活性被认为是有益的。

在我们之前的回顾中，PubMed确定了1987年至2012年间16项关于放疗中补充硒的临床研究。我们得出结论，补充硒可提高血硒水平，改善生活质量，预防或减少放射治疗的副作用，并且不会降低放射治疗的效果或引起任何毒性。为了建立放射治疗中硒补充的指南，我们通过临床研究的最新进展评估了放射治疗中硒补充的益处和风险。

本研究的结果有力地支持了以下结论：

口服剂量为200-500μg的硒，可提高血液硒水平，改善生活质量，预防或减少放射治疗的副作用，且不会降低放射治疗的效果或引起毒性。在癌症患者中，硒的水平往往较低，并且由于近期的放疗、败血症或其他一些病理并发症，使硒的水平进一步降低。