背景:头颈癌的调强放疗(IMRT)导致正常组织的放疗剂量减少,像唾液腺一样,同时保持较高的局部控制率。口腔粘膜和皮肤毒性仍然是治疗相关发病率的主要来源。发生在大多数患者身上。
目的:我们进行了剂量学可行性研究,目的是建立一种理论上可以减少皮肤和口腔粘膜辐射剂量的方法,同时保持对其他危险器官的类似回避,和规划目标量(PTV)覆盖率。
方法:使用光子优化器(PO)15.6版和AcurosXB剂量计算算法,在TrueBeamSTx上使用共面VMAT弧重新扫描先前治疗的患者的临床计划。在三种方法之间进行了比较:“传统,\"\"皮肤保护\"和皮肤/粘膜避免(\"SMART\")技术,使用方差分析比较剂量指标,使用Bonferroni校正来解释多个成对比较。治疗期间粘膜炎和放射性皮炎的最大等级与不同的剂量-体积指标相关,以预测什么可能有临床意义。
结果:16名患者符合研究标准,并使用皮肤保护和SMART技术进行了重新检查。皮肤备用结构的最大剂量从64.2Gy减少到56.6和55.9Gy,在保留皮肤和SMART计划中(p<0.0001),平均剂量从26.7Gy减少到20.0和20.2Gy,分别(p<0.0001)。两种技术均未降低口腔结构的最大剂量,然而,通过SMART技术,口腔结构的平均剂量从39.03Gy降至33.5Gy(p<0.0001).在SMART计划中,PTV_V95%的覆盖率略有下降(99.52%与98.79%,p=0.0073),和类似的轻微减少PTV_低覆盖率V95%的皮肤保留和SMART计划(99.74%与97.89%与97.42%,p<0.0001)。不同技术对有风险器官的最大剂量没有统计学差异。放疗期间口腔剂量与最大等级相关。剂量的Spearman相关系数为20%,50%,80%的口腔体积为0.5(p=0.048),0.64(p=0.007),和0.62(p=0.010),分别。仅发现皮肤毒性等级与皮肤保留结构的D20%相关(Spearman相关系数为0.58,p=0.0177)。
结论:SMART技术似乎能够减少最大和平均皮肤剂量,以及平均口腔剂量,虽然只是稍微减少了PTV的覆盖范围,可接受的OAR剂量。我们认为这些改进需要在临床试验中进行调查。
BACKGROUND: Intensity modulated radiotherapy (IMRT) for head and neck cancer has led to a reduction in radiotherapy doses to normal tissues, like the salivary glands, while maintaining high rates of local control. Oral mucosal and skin toxicity is still a major source of treatment-related morbidity, occurring in most patients.
OBJECTIVE: We conducted a dosimetric feasibility
study with the goal of creating a methodology that could theoretically reduce the dose of radiation to skin and oral
mucosa, while maintaining comparable avoidance of other organs at risk, and planning target volume (PTV) coverage.
METHODS: The clinical plans of patients treated previously were replanned using coplanar VMAT arcs on a TrueBeam STx using the photon optimizer (PO) version 15.6 and the Acuros XB dose calculation algorithm. Comparisons were made between three methodologies: \"Conventional,\" \"Skin Sparing\" and a skin/
mucosa avoiding (\"SMART\") technique, with dose metrics being compared using analysis of variance, with a Bonferroni correction to account for multiple pairwise comparisons. The maximum grade of mucositis and radiation dermatitis during treatment was correlated to different dose-volume metrics to predict what could be clinically meaningful.
RESULTS: Sixteen patients met the
study criteria and were replanned using the skin sparing and SMART techniques. Maximum doses to the skin sparing structure were reduced from 64.2 Gy to 56.6 and 55.9 Gy, in the skin sparing and SMART plans (p < 0.0001), and mean doses reduced from 26.7 Gy to 20.0 and 20.2 Gy, respectively (p < 0.0001). Maximum doses to the oral cavity structure were not reduced by either technique, however mean dose to the oral cavity structure was reduced from 39.03 Gy to 33.5 Gy by the SMART technique (p < 0.0001). There was a slight reduction in PTV_High coverage by the V95% in the SMART plans (99.52% vs. 98.79%, p = 0.0073), and a similar slight reduction in PTV_Low coverage by the V95% by both the skin sparing and SMART plans (99.74% vs. 97.89% vs. 97.42%, p < 0.0001). Maximum doses to organs at risk were not statistically different between techniques. Dose to oral cavity and maximum grade experienced during radiotherapy correlated. The Spearman correlation coefficient for dose to 20%, 50%, and 80% of the volume of oral cavity was 0.5 (p = 0.048), 0.64 (p = 0.007), and 0.62 (p = 0.010), respectively. Skin toxicity grade was only found to be correlated with the D20% of the skin sparing structure (Spearman correlation coefficient of 0.58, p = 0.0177).
CONCLUSIONS: The SMART technique appears to be able to reduce maximum and mean skin dose, as well as mean oral cavity doses, while only slightly reducing PTV coverage, with acceptable OAR doses. We feel the improvements warrant investigation in a clinical
trial.