Zhang Yingting, Lin Chengguang, Wu Jianhua, Jiang Xiaobo, Lee Shara W Y, Tam Shing-Yau, Wu Vincent W C
State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou, China.
Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hong Kong SAR, China.
J Med Radiat Sci. 2017 Sep;64(3):188-194. doi: 10.1002/jmrs.209. Epub 2017 Mar 4.
Radiotherapy of nasopharyngeal carcinoma patients with parapharyngeal space (PPS) involvement may deliver high dose to the parotid gland. This study evaluated parotid gland changes during and up to 3 months after radiotherapy.
Kilovoltage computed tomography (CT) scans of head and neck region of 39 nasopharyngeal carcinoma patients with PPS involvement were performed at pre-radiotherapy, 10th, 20th and 30th fractions and 3 months after treatment. The parotid glands were contoured in pre-radiotherapy planning CT scan and in subsequent scans. Dice similarity coefficient (DSC), percentage volume change and centroid movement between the planning CT and the subsequent CTs were obtained from the contouring software. In addition, the distance between medial and lateral borders of parotid glands from the mid-line at various time intervals were also measured.
The ipsilateral parotid gland received a mean dose of about 5 Gy higher than the contralateral side. The mean DSC and parotid volume decreased by more than 30% at 20th fraction and reached the minimum at 30th fraction. Partial recovery was observed at 3 months after treatment. The centroid displacement followed a similar pattern, which moved medially and superiorly by an average of 0.30 cm and 0.18 cm, respectively, at 30th fraction. The changes in ipsilateral gland were slightly greater than the contralateral side.
Substantial volume change and medial movement of parotid gland were observed with slightly greater magnitude in the ipsilateral side. Adaptive radiotherapy was suggested at around 15th to 20th fraction so as to optimise the original dose distribution of the plan.
鼻咽癌累及咽旁间隙（PPS）的患者在放疗时腮腺可能会受到高剂量照射。本研究评估了放疗期间及放疗后3个月内腮腺的变化。
对39例累及PPS的鼻咽癌患者在放疗前、放疗第10次、第20次、第30次时以及治疗后3个月进行头颈区域的千伏计算机断层扫描（CT）。在放疗前计划CT扫描及后续扫描中勾勒出腮腺轮廓。从轮廓软件中获取计划CT与后续CT之间的骰子相似系数（DSC）、体积变化百分比和质心移动情况。此外，还测量了不同时间间隔腮腺内侧和外侧边界距中线的距离。
同侧腮腺平均受量比 contralateral 侧高约5 Gy。第20次放疗时平均DSC和腮腺体积下降超过30%，并在第30次放疗时达到最小值。治疗后3个月观察到部分恢复。质心位移呈现类似模式，在第30次放疗时分别平均向内和向上移动0.30 cm和0.18 cm。同侧腺体的变化略大于 contralateral 侧。
观察到腮腺有明显的体积变化和向内移动，同侧变化幅度略大。建议在放疗第15至20次左右进行自适应放疗，以优化计划的原始剂量分布。
