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首页> 外文期刊>Radiotherapy and oncology: Journal of the European Society for Therapeutic Radiology and Oncology >Dose-response relationships within the parotid gland after radiotherapy for head and neck cancer.
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Dose-response relationships within the parotid gland after radiotherapy for head and neck cancer.

机译：头颈癌放疗后腮腺内的剂量反应关系。

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摘要

BACKGROUND AND PURPOSE: To determine the salivary function, after parotid-sparing radiotherapy (RT), of different regions within the parotid gland and to evaluate dose-function relationships within the parotid glands and between patients. PATIENTS AND METHODS: Sixteen head and neck cancer patients, irradiated between September 1999 and November 2000 using a conformal parotid-sparing technique, were included in this study. Before RT and 7 months after RT (range 6-10 months), a salivary gland scintigraphy was performed in all patients combined with a single photon emission computed tomography (SPECT). The salivary excretion fraction (SEF) was measured, after stimulation, in 8-12 transverse 5mm SPECT slices of each parotid. Loss of salivary excretion fraction (dSEF %) of these slices was calculated as the proportion of SEF after RT as compared to SEF before RT. Since the planning CT-scan and the SPECT-scintigraphy were performed in the same treatment position, the dose to a transverse slice within the parotid gland could be matched to the loss of salivary excretion fraction of that respective slice. A non-linear model was fitted to the dose-loss of function data and the dose resulting in 50% loss of salivary excretion fraction (D(50)) was calculated. RESULTS: Before RT, all but one patient presented with normal salivary excretion fractions (SEF) of both parotid glands. Within the same parotid gland, the SEF's of the different slices were almost equal. Seven months after RT, the reduction in SEF was statistically significant (P-value <0.0001). A significant difference in loss of salivary excretion fraction (dSEF) was also observed between both parotid glands (P<0.0001) as a result of the parotid-sparing technique. When plotting the dSEF of a slice versus the dose given to that slice, doses as low as 10-15Gy could result in a serious loss of function (dSEF >50%). After fitting a non-linear model to these plots, the mean dose resulting in 50% loss of salivary excretion fraction (D(50)) 7 months after RT was 22.5Gy. A large inter-patient variability was found in D(50). CONCLUSIONS: Salivary SPECT is a useful tool for the evaluation of the salivary function of different slices within the parotid gland. Before irradiation, the different slices within one parotid gland act as functional sub-units contributing equally to the function of the entire gland. Seven months after an average dose of 22.5Gy (D(50)) the functional sub-unit has lost 50% of its excretion fraction. The high inter-patient variability in D(50) and the observation that low doses (10-15Gy) can induce serious loss of function should prompt us in the clinic to reduce the dose to the parotids even lower than the threshold of 22.5Gy.
机译：背景与目的：在腮腺保留放疗（RT）之后，确定腮腺内不同区域的唾液功能，并评估腮腺内以及患者之间的剂量-功能关系。患者与方法：本研究包括1999年9月至2000年11月之间使用保形腮腺保形技术照射的16例头颈癌患者。在放疗前和放疗后7个月（范围6-10个月），所有患者均进行了唾液腺闪烁显像，并结合了单光子发射计算机断层扫描（SPECT）。刺激后，在每个腮腺的8-12个横向5mm SPECT切片中测量唾液排泄分数（SEF）。将这些切片的唾液排泄分数损失（dSEF％）计算为RT后SEF与RT前SEF的比例。由于计划的CT扫描和SPECT闪烁照相术是在相同的治疗位置进行的，因此腮腺内横向切片的剂量可以与相应切片唾液排泄分数的损失相匹配。将非线性模型拟合到功能数据的剂量损失，并计算导致唾液排泄分数（D（50））损失50％的剂量。结果：在放疗前，除一名患者外，所有腮腺的唾液排泄分数（SEF）均正常。在同一腮腺中，不同切片的SEF几乎相等。放疗后七个月，SEF的降低具有统计学意义（P值<0.0001）。由于腮腺保留技术，两个腮腺之间的唾液排泄分数（dSEF）损失也存在显着差异（P <0.0001）。将切片的dSEF与该切片的剂量作图时，低至10-15Gy的剂量可能会导致严重的功能丧失（dSEF> 50％）。对这些图拟合非线性模型后，RT后7个月导致唾液排泄分数（D（50））损失50％的平均剂量为22.5Gy。在D（50）中发现较大的患者间差异。结论：唾液SPECT是评估腮腺中不同切片的唾液功能的有用工具。在辐照之前，一个腮腺内的不同切片起着功能性亚基的作用，对整个腺体的功能起着同等作用。平均剂量22.5Gy（D（50））七个月后，该功能性亚基的排泄分数降低了50％。 D（50）患者之间的高变异性以及低剂量（10-15Gy）可能导致严重功能丧失的观察结果应促使我们在临床中减少腮腺的剂量，甚至低于22.5Gy的阈值。

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