Robustness of patient positioning for interfractional error in carbon ion radiotherapy for stage I lung cancer: Bone matching versus tumor matching.

Abstract

BACKGROUND AND PURPOSE:

Patient positioning was compared by tumor matching (TM) and conventional bony structure matching (BM) in carbon ion radiotherapy for stage I non-small cell lung cancer to evaluate the robustness of TM and BM in determining interfractional error.

MATERIAL AND METHODS:

Sixty irradiation fields were analyzed. Computed tomography (CT) images acquired before treatment initiation for confirmation (Conf-CT) were obtained under the same settings as the treatment planning CT images and used to evaluate both positioning methods. The dose distributions were recalculated for Conf-CT using both BM and TM, and the dose-volume histogram parameters [V95% of clinical target volume, V5Gy(RBE) of normal lung, and acceptance ratio (ratio of cases with V95% > 95%)] were evaluated. The required margin, which in 90% of cases achieved the acceptable condition, was also examined.

RESULTS:

Using BM and TM, the median V95% was 98.93% and 100% (p < 0.001) and the mean V5Gy(RBE) was 135.9 and 125.8 (p = 0.694), respectively. The estimated required margins were 7.9 and 3.3 mm and increased by 53.9% and 2.5% of V5Gy(RBE), respectively, compared with planning.

CONCLUSIONS:

TM ensured a better dose distribution than did BM. To enable TM, volumetric imaging is crucial and should replace 2D radiographs for carbon therapy of stage I lung cancer.

• Authors: Makoto Sakai, Yoshiki Kubota, Jun-Ichi Saitoh, Daisuke Irie, Katsuyuki Shirai, Ryosuke Okada, Masami Torikoshi, Tatsuya Ohno, Takashi Nakano
• Journal: Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology (Radiother Oncol) Vol. 129 Issue 1 Pg. 95-100 (10 2018) ISSN: 1879-0887 [Electronic] Ireland
• PMID: 29100701 (Publication Type: Comparative Study, Evaluation Study, Journal Article)
• Copyright: Copyright © 2017 Elsevier B.V. All rights reserved.

Topics

• Aged
• Aged, 80 and over
• Bone and Bones (radiation effects)
• Carcinoma, Non-Small-Cell Lung (radiotherapy)
• Female
• Heavy Ion Radiotherapy (methods)
• Humans
• Lung (radiation effects)
• Lung Neoplasms (radiotherapy)
• Male
• Middle Aged
• Patient Positioning (methods)
• Radiotherapy Dosage
• Radiotherapy Planning, Computer-Assisted (methods)
• Tomography, X-Ray Computed