由SABR再论放射敏感性

随着现代放射治疗技术进步，放疗已由过去二维时代进入三维和四维时代，治疗精度大幅度提高，分割模式也发生了深刻变革。从传统放射治疗发展到以三维适形放射治疗（3D-CRT）和调强放射治疗（IMRT）为代表的聚焦照射，提高了肿瘤靶区剂量，减少了正常组织的损伤。同时随着影像引导技术进步，治疗机与影像引导结合，每次治疗前通过影像扫描技术获得肿瘤靶区位置信息，或用4D影像引导技术精确地将射线投射到目标靶点，达到立体定向体部放射治疗（stereotactic body radiation therapy，SBRT）/立体定向消融放疗（stereotactic ablative radiotherapy，SABR）的目的，放射治疗完全进入精准、高效和低毒时代。高剂量、大分割照射已经取得令人信服和可喜的疗效，传统放射生物学理论已无法解释这种照射模式抗肿瘤细胞作用机制。传统放疗认为，肿瘤有敏感与不敏感之分，但是，进入SABR时代，肿瘤对其治疗均反应良好，放射治疗学迫切需要建立新的放射生物学学说和体系，在传统放射生物学理论基础上，更好地阐明新技术原理、作用机制，并建立与传统放射生物学内在联系，为临床普及和推广消融放疗技术奠定理论基础。

Review of tumor radiosensitivity from the point of view of stereotactic ablative radiotherapy

With the technical advances, radiotherapy has ushered in a new era of 3-D and 4D, which are associated with significantly improved therapy precision and profound change in fractionation pattern. The radiotherapy with focused rays, represented by both 3D-conformal radiotherapy (3D-CRT) and intensity modulated radiation therapy (IMRT), involves the delivery of high doses to the target volume, with a less attendant potential for damages to surrounding normal tissue. Radiotherapy has been able to deliver precise, efficient, low toxic access to therapeutic effects thanks to the advance in image-guided techniques, the combination of radiotherapy equipment with image-guided system, the availability of target position information before radiotherapy with 3D or 4D image modality, the stereotactic body radiation therapy (SBRT)/the stereotactic ablation radiosurgery (SABR). Conventional fractionated radiation has seen the therapeutic effect of convincing and promising. The conventional theory of radiobiology, which deems the tumor not sensitive to radiotherapy to have good reaction with SABR, has been unable to explain the mechanism of antitumor effects arising from such exposure modes. Therefore, it is now urgent to create new radiobiological theory and system for radiotherapy in order to better illustrate the principle and mechanism of new technologies, to establish its internal relation with conventional radiobiology and to lay theoretical groundwork for popularization and dissemination of SABR in clinical medicine.