Anatomical and dosimetric variations during volumetric modulated arc therapy in patients with locally advanced nasopharyngeal carcinoma after induction therapy: Implications for adaptive radiation therapy

IF 2.7 3区医学 Q3 ONCOLOGY

Clinical and Translational Radiation Oncology Pub Date : 2024-09-17 DOI:10.1016/j.ctro.2024.100861

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引用次数: 0

Abstract

Purpose

To investigate anatomical and dosimetric changes during volumetric modulated arc therapy (VMAT) in patients with locally advanced nasopharyngeal carcinoma (LA-NPC) after induction therapy (IT) and explore characteristics of patients with notable variations.

Materials and methods

From July 2021 to June 2023, 60 LA-NPC patients undergoing VMAT after IT were retrospectively recruited. Adaptive computed tomography (aCT), reconstructed from weekly cone-beam computed tomography(CBCT), facilitates recontouring and planning transplantation. Volume, dice similarity coefficients, and dose to target volumes and organs at risk(OARs) on planning CT(pCT) and aCT were compared to identify changing patterns. Multivariate logistic regression was used to investigate risk factors.

Results

The volumes of PGTVnasopharynx (PGTVp), PGTVnode (PGTVn), ipsilateral and contralateral parotid glands decreased during VMAT, with reductions of 2.25 %, 6.98 %, 20.09 % and 18.00 %, respectively, at 30 fractions from baseline (P < 0.001). After 25 fractions, D99 and D95 of PGTVn decreased by 7.94 % and 4.18 % from baseline, respectively, while the Dmean of ipsilateral and contralateral parotid glands increased by 7.80 % and 6.50 %, marking the peak rates of dosimetric variations (P < 0.001). The dosimetric fluctuations in PGTVp, the brainstem, and the spinal cord remained within acceptable limits. Furthermore, an initial BMI ≥ 23.5 kg/m² and not-achieving objective response (OR) after IT were regarded as risk factors for a remarkable PGTVn dose reduction in the later stages of VMAT.

Conclusions

Replanning for post-IT LA-NPC patients appears reasonable at 25F during VMAT. Patients with an initial BMI ≥ 23.5 kg/m² and not-achieving OR after IT should be considered for adaptive radiation therapy to stabilize the delivered dose.

查看原文本刊更多论文

局部晚期鼻咽癌患者在诱导治疗后接受容积调制弧治疗期间的解剖和剂量变化：适应性放射治疗的意义

目的研究诱导治疗（IT）后局部晚期鼻咽癌（LA-NPC）患者在容积调控弧治疗（VMAT）期间的解剖学和剂量学变化，并探索有显著变化的患者的特征。材料和方法从2021年7月到2023年6月，回顾性招募了60名IT后接受VMAT治疗的LA-NPC患者。根据每周锥束计算机断层扫描（CBCT）重建的自适应计算机断层扫描（aCT）有助于重新构图和规划移植。比较了计划 CT（pCT）和 aCT 的体积、骰子相似系数以及目标体积和危险器官（OAR）的剂量，以确定变化的模式。结果在 VMAT 期间，PGTVnasopharynx (PGTVp)、PGTVnode (PGTVn)、同侧和对侧腮腺的体积均有所减少，在 30 次分割时，与基线相比分别减少了 2.25 %、6.98 %、20.09 % 和 18.00 %（P < 0.001）。25 个分次后，PGTVn 的 D99 和 D95 分别比基线下降了 7.94 % 和 4.18 %，而同侧和对侧腮腺的 Dmean 则分别上升了 7.80 % 和 6.50 %，达到了剂量变化的峰值（P <0.001）。PGTVp、脑干和脊髓的剂量波动仍在可接受范围内。此外，初始 BMI ≥ 23.5 kg/m2 和 IT 后未达到客观反应 (OR) 被视为 VMAT 后期 PGTVn 剂量显著降低的风险因素。初始 BMI ≥ 23.5 kg/m2 和 IT 后未达到 OR 的患者应考虑进行适应性放疗，以稳定给药剂量。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Clinical and Translational Radiation Oncology Medicine-Radiology, Nuclear Medicine and Imaging

CiteScore

5.30

自引率

3.20%

发文量

114

审稿时长

40 days