Physics Department, Faculty of Science, King Abdul-Aziz University, Jeddah, Saudi Arabia.
Medical Physics Unit, Radiology and Intervention Dept, Faculty of Medicine, Alexandria University, Egypt.
J Xray Sci Technol. 2019;27(3):473-483. doi: 10.3233/XST-180468.
Cervical cancer radiotherapy is usually administrated through 3-Dimensional Conformal Radiation Therapy (3DCRT) followed by a brachytherapy (BT) boost.
To investigate whether Volumetric Modulated Arc Therapy (VMAT) can replace High Dose Rate (HDR) intracavitary BT boost for patients undergoing cervical cancer radiotherapy.
Computed Tomography (CT) images for ten patients with tandem and ovoids were included in this study. Target volumes, rectum, bladder, sigmoid, small bowel and both femoral heads were delineated. Two plans were carried out including (a) a BT plan optimized manually by modifying dwell time and Ir-192 source positions, (b) a VMAT plan generated using two partial arcs with 10 MV photon beam. The prescribed dose was 7 Gy. The relevant dose volume parameters (DVPs) of target volumes and OARs for the two plans were analyzed statistically using SPSS Wilcoxon Signed Rank test.
VMAT plan showed a significant reduction of 9.1%, 9.3%, 15.4%, 14.4% and 13.1% in rectum maximum dose, rectum D2cc, bladder maximum dose, bladder D2cc and sigmoid maximum dose (P < 0.05). VMAT and BT plans showed comparable D2cc of sigmoid and small bowel maximum doses (P = 0.333 and P = 0.646). On the other hand, VMAT showed significantly higher small bowel D2cc and maximum point dose for both femoral heads comparing to BT plan (P < 0.05). Also, VMAT plan yielded greater homogeneous target coverage compared to BT plan (P < 0.05).
The study demonstrated that VMAT plan achieves significant dose reduction of rectum, bladder and sigmoid, as well as superior homogeneous target coverage compared to BT plan. On the other hand, VMAT delivers more radiation exposures to small bowel and femoral heads.
宫颈癌放疗通常采用三维适形放疗（3DCRT）联合近距离放疗（BT）加量。
探讨容积旋转调强放疗（VMAT）是否可以替代高剂量率（HDR）腔内 BT 加量治疗宫颈癌患者。
纳入 10 例使用 T 型和宫腔施源器的宫颈癌患者，勾画靶区、直肠、膀胱、乙状结肠、小肠和双侧股骨头。分别制定 BT 计划（通过修改驻留时间和 Ir-192 源位置进行手动优化）和 VMAT 计划（使用 10MV 光子束进行两个部分弧照射），处方剂量为 7Gy。使用 SPSS Wilcoxon 符号秩检验对两种计划的靶区和 OAR 的相关剂量体积参数（DVPs）进行统计学分析。
VMAT 计划使直肠最大剂量、直肠 D2cc、膀胱最大剂量、膀胱 D2cc 和乙状结肠最大剂量分别显著降低 9.1%、9.3%、15.4%、14.4%和 13.1%（P<0.05）。VMAT 计划和 BT 计划的乙状结肠和小肠最大剂量 D2cc 无显著差异（P=0.333 和 P=0.646）。另一方面，VMAT 计划使双侧股骨头的小肠 D2cc 和最大点剂量显著升高（P<0.05）。此外，VMAT 计划的靶区均匀性优于 BT 计划（P<0.05）。
与 BT 计划相比，VMAT 计划能显著降低直肠、膀胱和乙状结肠的剂量，同时具有更好的靶区均匀性。但 VMAT 计划会增加小肠和股骨头的照射剂量。
