在分次内解剖变化存在的情况下，宫颈癌计划库和在线 MRI 引导放疗的剂量学比较。
Dosimetric comparison of library of plans and online MRI-guided radiotherapy of cervical cancer in the presence of intrafraction anatomical changes.
机构信息
Department of Radiation Oncology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, the Netherlands.
Present Address: Radiotherapeutisch Instituut Friesland, Borniastraat 36, Leeuwarden, the Netherlands.
出版信息
Radiat Oncol. 2019 Jul 12;14(1):126. doi: 10.1186/s13014-019-1322-0.
BACKGROUND
Online magnetic resonance imaging (MRI)-guided radiotherapy of cervical cancer has the potential to further reduce dose to organs at risk (OAR) as compared to a library of plans (LOP) approach. This study presents a dosimetric comparison of an MRI-guided strategy with a LOP strategy taking intrafraction anatomical changes into account.
METHODS
The 14 patients included in this study were treated with chemo radiation at our institute and received weekly MRIs after informed consent. The MRI-guided strategy consisted of treatment plans created on the weekly sagittal MRI with 3 mm and 5 mm planning target volume (PTV) margin for clinical target volume (CTV) cervix-uterus (MRI_3mm and MRI_5mm). The plans for the LOP strategy were based on interpolations of CTV cervix-uterus on pretreatment full and empty bladder scans. Dose volume histogram (DVH) parameters were compared for targets and OARs as delineated on the weekly transversal MRI, which was acquired on average 10 min after the sagittal MRI.
RESULTS
For the MRI_5mm strategy D of the high-risk CTV was at least 95% for all weekly MRIs of all patients, while for the LOP and MRI_3mm strategy this requirement was not satisfied for at least one weekly MRI for 1 and 3 patients, respectively. The average reduction of the volume of the reference dose (95% of the prescribed dose) as compared to the LOP strategy was 464 cm for the MRI_3mm strategy, and 422 cm for the MRI_5mm strategy. The bowel bag constraint V < 350 cm was violated for 13 patients for the LOP strategy and for 5 patients for both MRI_3mm and MRI_5mm strategy.
CONCLUSIONS
With online MRI-guided radiotherapy of cervical cancer considerable sparing of OARs can be achieved. If a new treatment plan can be generated and delivered within 10 min, an online MRI-guided strategy with a 5 mm PTV margin for CTV cervix-uterus is sufficient to account for intrafraction anatomical changes.
TRIAL REGISTRATION
NL44492.018.13.
背景
与基于计划库（LOP）的方法相比，在线磁共振成像（MRI）引导的宫颈癌放射治疗有可能进一步降低危及器官（OAR）的剂量。本研究介绍了一种考虑分次内解剖变化的 MRI 引导策略与 LOP 策略的剂量学比较。
方法
本研究纳入了在我院接受化疗和放疗的 14 名患者，在知情同意后每周接受 MRI 检查。MRI 引导策略包括在每周矢状 MRI 上创建治疗计划，CTV 宫颈-子宫采用 3mm 和 5mm 计划靶区（PTV）边界（MRI_3mm 和 MRI_5mm）。LOP 策略的计划基于预处理全膀胱和空膀胱扫描时 CTV 宫颈-子宫的插值。基于每周横断面 MRI 比较了目标和 OAR 的剂量体积直方图（DVH）参数，该横断面 MRI 是在矢状 MRI 后平均 10 分钟采集的。
结果
对于 MRI_5mm 策略，所有患者的所有每周 MRI 中，高危 CTV 的 D 至少为 95%，而对于 LOP 和 MRI_3mm 策略，至少有 1 名患者和 3 名患者的至少 1 次每周 MRI 不满足这一要求。与 LOP 策略相比，MRI_3mm 策略的参考剂量（处方剂量的 95%）体积平均减少 464cm，MRI_5mm 策略的参考剂量体积平均减少 422cm。对于 LOP 策略，有 13 名患者的肠袋体积 V<350cm³受到限制，而对于 MRI_3mm 和 MRI_5mm 策略，有 5 名患者的肠袋体积 V<350cm³受到限制。
结论
对于宫颈癌的在线 MRI 引导放疗，可以实现 OAR 的大量保护。如果可以在 10 分钟内生成和交付新的治疗计划，则对于 CTV 宫颈-子宫采用 5mm PTV 边界的在线 MRI 引导策略足以考虑分次内解剖变化。
试验注册
NL44492.018.13.
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