Houweling Antonetta C, Dijkema Tim, Roesink Judith M, Terhaard Chris H J, Raaijmakers Cornelis P J
Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands.
Radiother Oncol. 2008 Oct;89(1):64-70. doi: 10.1016/j.radonc.2008.04.008. Epub 2008 May 22.
The submandibular glands are proposed to be important in preventing xerostomia in head-and-neck cancer patients. We investigated the feasibility of sparing the contralateral submandibular gland (cSMG) by reducing the dose to the contralateral planning target volume (PTV) and by reducing the clinical target volume (CTV)-to-PTV margin.
Ten oropharyngeal cancer patients with a contralateral elective PTV were included in this planning study, using intensity modulated radiotherapy (IMRT). The effect on the mean dose to the cSMG of reducing the dose coverage to the contralateral elective PTV from 95 to 90% of the prescribed dose (54Gy in 1.8Gy daily fractions) was determined. The influence of reducing the margin for position uncertainty from 5 to 2mm was investigated.
The mean dose to the cSMG was reduced from 54Gy to approximately 40Gy if the dose coverage to the contralateral PTV was reduced to 90% of the prescribed dose. The estimated normal tissue complication probability (NTCP) was reduced below 50%. Reducing the margin from 5 to 2mm resulted in a decrease in the mean dose to the cSMG of approximately 6Gy.
Reducing the mean dose to the cSMG below 40Gy is possible with a reasonable dose coverage of the contralateral elective PTV.
有观点认为颌下腺在预防头颈癌患者口干症方面具有重要作用。我们通过降低对侧计划靶体积（PTV）的剂量以及缩小临床靶体积（CTV）至PTV的边界，研究保留对侧颌下腺（cSMG）的可行性。
本计划研究纳入了10例有对侧选择性PTV的口咽癌患者，采用调强放疗（IMRT）。确定将对侧选择性PTV的剂量覆盖范围从处方剂量（每日分次给予1.8Gy，共54Gy）的95%降至90%对cSMG平均剂量的影响。研究将位置不确定边界从5mm缩小至2mm的影响。
如果将对侧PTV的剂量覆盖范围降至处方剂量的90%，cSMG的平均剂量从54Gy降至约40Gy。估计的正常组织并发症概率（NTCP）降至50%以下。将边界从5mm缩小至2mm导致cSMG的平均剂量降低约6Gy。
通过合理覆盖对侧选择性PTV，有可能将cSMG的平均剂量降至40Gy以下。
