Elsevier

Radiotherapy and Oncology

Volume 144, March 2020, Pages 224-230
Radiotherapy and Oncology

Original Article
Dose assessment for patients with stage I non-small cell lung cancer receiving passive scattering carbon-ion radiotherapy using daily computed tomographic images: A prospective study

https://doi.org/10.1016/j.radonc.2020.01.003Get rights and content
Under a Creative Commons license
open access

Highlights

  • All patients’ accumulated doses were satisfactory using tumor matching.

  • Bone matching may lead to hypofractionated carbon ion therapy failure.

  • Tumor matching enables a smaller required margin.

  • Daily CT alignment is necessary for patients with non-small cell lung cancer.

Abstract

Background and purpose

This study aimed to assess dose distributions for stage I non-small cell lung cancer (NSCLC) with passive scattering carbon-ion radiotherapy (C-ion RT) using daily computed tomography (CT) images.

Materials and methods

We enrolled 10 patients with stage I NSCLC and acquired a total of 40 pre-fractional CT image series under the same settings as the planning CT images. These CT images were registered with planning CT images for dose evaluation using both bone matching (BM) and tumor matching (TM). Using deformable image registration, we generated accumulated doses. Moreover, the volumetric dose parameters were compared in terms of tumor coverage and lung exposure and statistical analyses were performed.

Results

Overall, 25% of 40 fractional dose distributions were unacceptable with BM, compared with 2.5% with TM (P < 0.001). Using BM, three patients’ accumulated dose distributions were unacceptable; however, all were satisfactory with TM (P < 0.001). No differences were observed in water-equivalent path length (WEL). The required margins in patients with poor dose distribution were 5.9 and 4.4 mm for BM and TM, respectively.

Conclusions

This study establishes that CT image-based TM is robust compared with conventional BM for both daily and accumulated dose distributions. The effects of changes in WEL seem to be limited. Hence, daily CT alignment is recommended for patients with stage I NSCLC receiving C-ion RT.

Keywords

Carbon-ion radiotherapy
Dose assessment
Tumor matching
Bone matching
Lung cancer

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