Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York.
Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York.
Int J Radiat Oncol Biol Phys. 2019 May 1;104(1):177-187. doi: 10.1016/j.ijrobp.2019.01.073. Epub 2019 Jan 23.
Spatially fractionated radiation therapy represents a significant departure from canonical thinking in radiation oncology despite having origins in the early 1900s. The original and most common implementation of spatially fractionated radiation therapy uses commercially available blocks or multileaf collimators to deliver a nonconfluent, sieve-like pattern of radiation to the target volume in a nonuniform dose distribution. Dosimetrically, this is parameterized by the ratio of the valley dose in cold spots to the peak dose in hot spots, or the valley-to-peak dose ratio. The radiobiologic mechanisms are postulated to involve radiation-induced bystander effects, microvascular alterations, and/or immunomodulation. Current indications include bulky or locally advanced disease that would not be amenable to conventional radiation or that has proved refractory to chemoradiation. Early-phase clinical trials have shown remarkable success, with some response rates >90% and minimal toxicity. This has promoted technological developments in 3-dimensional formats (LATTICE), micron-size beams (microbeam), and proton arrays. Nevertheless, more clinical and biological data are needed to specify ideal dosimetry parameters and to formulate robust clinical indications and guidelines for optimal standardized care.
尽管时空分割放射治疗起源于 20 世纪初，但它代表了放射肿瘤学中对经典思维的重大突破。时空分割放射治疗的最初和最常见的实现方法是使用市售的挡块或多叶准直器，以非均匀剂量分布向靶区递送非融合的、筛状的放射模式。从剂量学角度来看，这可以通过冷点的谷剂量与热点的峰剂量之比，或者谷峰剂量比来参数化。其放射生物学机制被假设涉及放射诱导的旁观者效应、微血管改变和/或免疫调节。目前的适应证包括体积较大或局部晚期疾病，这些疾病不适宜常规放射治疗或对放化疗有抗药性。早期临床试验取得了显著成功，一些缓解率>90%，毒性最小。这促进了三维格式（LATTICE）、微米级光束（微束）和质子阵列等技术的发展。然而，还需要更多的临床和生物学数据来确定理想的剂量学参数，并为最佳标准化治疗制定稳健的临床适应证和指南。
