Hermans Bregtje C M, Persoon Lucas C G G, Podesta Mark, Hoebers Frank J P, Verhaegen Frank, Troost Esther G C
a Department of Radiation Oncology (MAASTRO clinic) , Maastricht University Medical Centre , Maastricht , the Netherlands.
b Helmholtz Zentrum Dresden-Rossendorf , Germany.
Acta Oncol. 2015;54(9):1483-9. doi: 10.3109/0284186X.2015.1061210. Epub 2015 Jul 29.
Use of highly conformal radiotherapy in patients with head and neck carcinoma may lead to under-/overdosage of gross target volume (GTV) and organs at risk (OAR) due to changes in patients' anatomy. A method to achieve more effective radiation treatment combined with less toxicity is dose-guided radiotherapy (DGRT). The aim of this study was to evaluate discrepancies between planned and actually delivered radiation dose in head and neck patients and to identify predictive factors.
In this retrospective analysis, 20 patients with cT2-4 N0-3 M0 carcinoma originating from oropharynx, oral cavity, larynx and hypopharynx (Cohort 1), and seven patients with cT1-4 N0-3 M0 nasopharyngeal carcinoma (Cohort 2) treated with primary (chemo)radiotherapy and undergoing weekly kV-CBCT scans were included. Radiation dose was recalculated on 184 kV-CBCT images, which was quantified by D95% (GTV), Dmean (parotid and submandibular glands) and D2% (spinal cord). Predictive factors investigated for changes in these dose metrics were: gender, age, cT/N-stage, tumor grade, HPV-status, systemic therapy, body mass index at start of treatment, weight loss and volume change over the duration of the radiotherapy.
There was no significant difference between the planned and delivered dose for GTV and OARs of Week 1 to subsequent weeks for Cohort 1. In Cohort 2, actually delivered Dmean to parotid glands was significant higher than planned dose (1.1 Gy, p = 0.002). No clinically relevant correlations between dose changes and predictive factors were found.
Weekly dose calculations do not seem to improve dose delivery for patients with tumors of the oral cavity, oropharynx, larynx and hypopharynx. In patients with nasopharyngeal carcinoma, however, mid-treatment imaging may facilitate DGRT.
头颈部癌患者使用高剂量适形放疗时，由于患者解剖结构的变化，可能导致大体肿瘤体积（GTV）和危及器官（OAR）的剂量不足/过量。一种能实现更有效放射治疗且毒性更小的方法是剂量引导放疗（DGRT）。本研究的目的是评估头颈部患者计划放射剂量与实际 delivered 放射剂量之间的差异，并确定预测因素。
在这项回顾性分析中，纳入了20例原发于口咽、口腔、喉和下咽的cT2 - 4 N0 - 3 M0癌患者（队列1），以及7例接受原发（化疗）放疗且每周进行千伏锥形束CT（kV - CBCT）扫描的cT1 - 4 N0 - 3 M0鼻咽癌患者（队列2）。在184 kV - CBCT图像上重新计算放射剂量，通过D95%（GTV）、平均剂量（腮腺和颌下腺）和D2%（脊髓）进行量化。针对这些剂量指标变化所研究的预测因素包括：性别、年龄、cT/N分期、肿瘤分级、人乳头瘤病毒（HPV）状态、全身治疗、治疗开始时的体重指数、体重减轻以及放疗期间的体积变化。
队列1中，第1周与后续几周的GTV和OAR的计划剂量与 delivered 剂量之间无显著差异。在队列2中，腮腺实际 delivered 的平均剂量显著高于计划剂量（1.1 Gy，p = 0.002）。未发现剂量变化与预测因素之间存在临床相关的相关性。
每周剂量计算似乎并未改善口腔、口咽、喉和下咽肿瘤患者的剂量 delivery。然而，对于鼻咽癌患者，治疗中期成像可能有助于DGRT。
