ABSTRACT
Objective To compare the dose distribution between volumetric-modulated arc therapy ( VMAT ) and intensity-modulated radiotherapy ( IMRT ) in patients with brain metastases receiving hippocampus-sparing whole brain radiotherapy. Methods Forty-six patients with brain metastases admitted to our hospital from 2013 to 2016 were recruited in this study. After fusing the CT and MRI images, the hippocampus was delineated on the fusion images. The three-grade hippocampal avoidance regions were created by using a volumetric expansion of 3,5 and 10 mm surrounding the hippocampus. The planning target volume ( PTV) was calculated by subtracting the 5-mm expansion surrounding the hippocampus from the whole brain. The prescription dose was 30 Gy/10 fractions. The 7-field IMRT and single arc VMAT were designed for each case. The dose distribution of PTV,hippocampus and other organs at risk ( OARs) were evaluated in both plans. Results The PTV was statistically compared between VMAT and IMRT:V95:95. 90％ and 94. 97％( P=0. 000 );V90:98. 17％ and 97. 48％( P=0. 000 );CI:0. 825 and 0. 813 ( P=0. 013);HI:0. 277 and 0. 289(P=0. 025).The hippocampal dose was also compared between VMAT and IMRT:the Dmax of hippocampus was 1698. 9 cGy for VMAT and 1784. 9 cGy for IMRT (P=0. 002).TheDmean of hippocampus was 1183. 8 cGy for VMAT and 1112. 7 cGy for IMRT (P=0. 000).No statistical significance was observed between IMRT and VMAT in protecting the OARs except the chiasma opticum ( 3262. 6 cGy and 3529. 3 cGy,P=0. 000).The MU and treatment time of VMAT and IMRT were 651 and 2768( P=0. 000) ,and 188 s and 504 s ( P=0. 000) . Conclusions The dose distribution of PTV in VMAT is significantly better than that in IMRT. VMAT is advantageous in protecting the hippocampus than IMRT. VMAT can significantly shorten treatment time and MU and enhance the equipment utilization. Besides, VMAT can achieve the goal of protecting the hippocampus and meet the prescription dose requirement of PTV.
ABSTRACT
Objective To preliminary investigate the clinical efficacy of whole brain simultaneous integrated boost intensity-modulated radiotherapy ( SIB-IMRT ) in patients diagnosed with brain metastases ( BM) . Methods Fifty-two cases of BM admitted to our hospital from January 2016 to December 2017 were equally recruited and randomly divided into the observation and control groups. Patients in the observation group were treated with SIB-IMRT, and those in the control group received conventional whole brain radiotherapy (WBRT).The clinical efficacy and prognosis were statistically compared between two groups. Results The ORR in the observation group was 77％, significantly higher than 27％ in the control group (P=0. 00).The median survival in the observation group was 384 d,significantly longer compared with 211 d in the control group (P=0. 00).All patients in both groups successfully completed corresponding treatment. Acute adverse reactions were mainly 1-2 grade reactions. Conclusions SIB-IMRT is an efficacious and safe treatment of BM,which yields tolerable adverse events and deserves application in clinical practice.
