头颈部癌适应性放疗对保留腮腺及降低口干风险的影响。
Impact of head and neck cancer adaptive radiotherapy to spare the parotid glands and decrease the risk of xerostomia.
作者信息
Castelli Joel, Simon Antoine, Louvel Guillaume, Henry Olivier, Chajon Enrique, Nassef Mohamed, Haigron Pascal, Cazoulat Guillaume, Ospina Juan David, Jegoux Franck, Benezery Karen, de Crevoisier Renaud
机构信息
Department of Radiotherapy, Centre Eugene Marquis, Avenue de la bataille Flandre Dunkerque, F-35000, Rennes, France.
Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France.
出版信息
Radiat Oncol. 2015 Jan 9;10:6. doi: 10.1186/s13014-014-0318-z.
BACKGROUND
Large anatomical variations occur during the course of intensity-modulated radiation therapy (IMRT) for locally advanced head and neck cancer (LAHNC). The risks are therefore a parotid glands (PG) overdose and a xerostomia increase. The purposes of the study were to estimate: - the PG overdose and the xerostomia risk increase during a "standard" IMRT (IMRTstd); - the benefits of an adaptive IMRT (ART) with weekly replanning to spare the PGs and limit the risk of xerostomia.
MATERIAL AND METHODS
Fifteen patients received radical IMRT (70 Gy) for LAHNC. Weekly CTs were used to estimate the dose distributions delivered during the treatment, corresponding either to the initial planning (IMRTstd) or to weekly replanning (ART). PGs dose were recalculated at the fraction, from the weekly CTs. PG cumulated doses were then estimated using deformable image registration. The following PG doses were compared: pre-treatment planned dose, per-treatment IMRTstd and ART. The corresponding estimated risks of xerostomia were also compared. Correlations between anatomical markers and dose differences were searched.
RESULTS
Compared to the initial planning, a PG overdose was observed during IMRTstd for 59% of the PGs, with an average increase of 3.7 Gy (10.0 Gy maximum) for the mean dose, and of 8.2% (23.9% maximum) for the risk of xerostomia. Compared to the initial planning, weekly replanning reduced the PG mean dose for all the patients (p<0.05). In the overirradiated PG group, weekly replanning reduced the mean dose by 5.1 Gy (12.2 Gy maximum) and the absolute risk of xerostomia by 11% (p<0.01) (30% maximum). The PG overdose and the dosimetric benefit of replanning increased with the tumor shrinkage and the neck thickness reduction (p<0.001).
CONCLUSION
During the course of LAHNC IMRT, around 60% of the PGs are overdosed of 4 Gy. Weekly replanning decreased the PG mean dose by 5 Gy, and therefore by 11% the xerostomia risk.
背景
在局部晚期头颈癌（LAHNC）的调强放射治疗（IMRT）过程中会出现较大的解剖学变异。因此，存在腮腺（PG）剂量过量和口干风险增加的问题。本研究的目的是评估：- “标准”IMRT（IMRTstd）期间PG剂量过量和口干风险增加情况；- 每周重新计划的自适应IMRT（ART）在保护PG并限制口干风险方面的益处。
材料与方法
15例LAHNC患者接受了根治性IMRT（70 Gy）治疗。每周进行CT扫描以评估治疗期间的剂量分布，分别对应初始计划（IMRTstd）或每周重新计划（ART）。从每周的CT扫描中重新计算分次照射时PG的剂量。然后使用可变形图像配准估计PG的累积剂量。比较以下PG剂量：治疗前计划剂量、每次治疗的IMRTstd和ART。还比较了相应的估计口干风险。寻找解剖学标记与剂量差异之间的相关性。
结果
与初始计划相比，在IMRTstd期间，59%的PG出现剂量过量，平均剂量平均增加3.7 Gy（最大增加10.0 Gy），口干风险平均增加8.2%（最大增加23.9%）。与初始计划相比，每周重新计划降低了所有患者的PG平均剂量（p<0.05）。在照射过量的PG组中，每周重新计划使平均剂量降低了5.1 Gy（最大降低12.2 Gy），口干的绝对风险降低了11%（p<0.01）（最大降低30%）。PG剂量过量和重新计划的剂量学益处随着肿瘤缩小和颈部厚度减小而增加（p<0.001）。
结论
在LAHNC的IMRT过程中，约60%的PG剂量过量4 Gy。每周重新计划使PG平均剂量降低了5 Gy，从而使口干风险降低了11%。
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