Nakano Hisashi, Takizawa Takeshi, Kawahara Daisuke, Tanabe Satoshi, Utsunomiya Satoru, Kaidu Motoki, Maruyama Katsuya, Takeuchi Shigekazu, Onda Kiyoshi, Koizumi Masahiko, Nishio Teiji, Ishikawa Hiroyuki
Department of Radiation Oncology, Institute of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima-shi, Hiroshima, Japan.
Department of Radiation Oncology, Niigata University Medical and Dental Hospital, 1-757 Asahimachi-dori, Chuo-ku, Niigata-shi, Niigata, Japan.
BJR Open. 2022 Nov 24;4(1):20220013. doi: 10.1259/bjro.20220013. eCollection 2022.
We evaluated the radiobiological effect of the irradiation time with the interruption time of stereotactic radiosurgery (SRS) using CyberKnife (CK) systemfor brain metastases.
We used the DICOM data and irradiation log file of the 10 patients with brain metastases from non-small-cell lung cancer (NSCLC) who underwent brain SRS. We defined the treatment time as the sum of the dose-delivery time and the interruption time during irradiations, and we used a microdosimetric kinetic model (MKM) to evaluate the radiobiological effects of the treatment time. The biological parameters, α, β, and the DNA repair constant rate ( + c), were acquired from NCI-H460 cell for the MKM. We calculated the radiobiological dose for the gross tumor volume (GTV) to evaluate the treatment time's effect compared with no treatment time as a reference. The D95 (%) and the Radiation Therapy Oncology Group conformity index (RCI) and Paddick conformity index (PCI) were calculated as dosimetric indices. We used several DNA repair constant rates ( + c) (0.46, 1.0, and 2.0) to assess the radiobiological effect by varying the DNA repair date ( + c) values.
The mean values of D95 (%), RCI, and PCI for GTV were 98.8%, 0.90, and 0.80, respectively, and decreased with increasing treatment time. The mean values of D95 (%), RCI, and PCI of GTV at 2.0 (a+c) value were 94.9%, 0.71, and 0.49, respectively.
The radiobiological effect of the treatment time on tumors was accurately evaluated with brain SRS using CK.
There has been no published investigation of the radiobiological impact of the longer treatment time with multiple interruptions of SRS using a CK on the target dose distribution in a comparison with the use of a linac. Radiobiological dose assessment that takes into account treatment time in the physical dose in this study may allow more accurate dose assessment in SRS for metastatic brain tumors using CK.
我们使用射波刀（CK）系统评估了立体定向放射外科治疗（SRS）的照射时间及中断时间对脑转移瘤的放射生物学效应。
我们使用了10例接受脑部SRS的非小细胞肺癌（NSCLC）脑转移患者的DICOM数据和照射日志文件。我们将治疗时间定义为剂量输送时间与照射期间中断时间之和，并使用微剂量动力学模型（MKM）来评估治疗时间的放射生物学效应。从NCI-H460细胞中获取用于MKM的生物学参数α、β和DNA修复常数率（+c）。我们计算了大体肿瘤体积（GTV）的放射生物学剂量，以评估与无治疗时间作为对照相比治疗时间的效应。计算D95（%）、放射治疗肿瘤学组适形指数（RCI）和帕迪克适形指数（PCI）作为剂量学指标。我们使用了几个DNA修复常数率（+c）（0.46、1.0和2.0），通过改变DNA修复日期（+c）值来评估放射生物学效应。
GTV的D95（%）、RCI和PCI的平均值分别为98.8%、0.90和0.80，且随治疗时间增加而降低。在2.0（a+c）值时，GTV的D95（%）、RCI和PCI的平均值分别为94.9%、0.71和0.49。
使用CK进行脑部SRS可准确评估治疗时间对肿瘤的放射生物学效应。
与使用直线加速器相比，尚未有关于使用CK进行多次中断的较长治疗时间对SRS靶区剂量分布的放射生物学影响的公开研究。本研究中考虑物理剂量中治疗时间的放射生物学剂量评估可能会使使用CK治疗转移性脑肿瘤的SRS剂量评估更准确。
