Feasibility of upright carbon ion radiotherapy for prostate cancer: Dosimetric comparison between supine and upright postures.

Authors

Yusuke Nomura, Taku Inaniwa, Yoshitake Yamada, Minoru Yamada, Yoichi Yokoyama, Hideyuki Mizuno, Shunsuke Yonai, Yoshiyuki Iwata, Kohei Oguma, Junichi Fukada, Naoyuki Shigematsu, Atsuya Takeda, Hitoshi Ishikawa, Masahiro Jinzaki

Published in

Medical physics. Volume 53. Issue 7. Pages e70555.

Abstract

Carbon ion radiotherapy (CIRT) in the upright posture is a treatment technique which delivers carbon ion beams from a fixed direction to patients who sit or stand on a rotating chair. Although various potential advantages of the upright positioning have been discussed, feasibility of upright CIRT for prostate cancer has not been quantitatively evaluated.
This study demonstrated prostate cancer CIRT in the upright posture and evaluated its feasibility by comparing anatomy and dosimetric metrics between the supine and upright postures.
A total of 12 pairs of computed tomography (CT) images of asymptomatic volunteers in the supine and upright postures were retrospectively analyzed. Based on a clinical treatment protocol, clinical target volume (CTV) was defined as being a prostate gland and proximal seminal vesicle. Other target and organ-at-risk (OAR) contours within a planning volume were also delineated. A CIRT plan was calculated for each CT volume with the same dose prescription and evaluation criteria. The delineated contour volumes, 16 dosimetric metrics, dose-volume histograms (DVHs) of CTV and OARs, and robustness against setup and range uncertainties were compared between the supine and upright postures.
No significant differences in the contour volumes were found between the two postures (p > 0.05). The CTV and rectum contour volumes were 34.30 ± 7.76 and 36.35 ± 13.53 cm³ for the supine posture and 35.89 ± 7.37 and 32.96 ± 8.08 cm³ for the upright posture, respectively. Moreover, mean absolute differences of five CTV dosimetric metrics (D2%, D5%, D50%, D95%, and D98%) were all less than 0.15 Gy (0.29% of the prescription dose of 51.6 Gy). Nine other dosimetric metrics in the upright posture were also equivalent to those in the supine posture. The DVHs and robustness in the upright posture were in agreement with those in the supine posture.
The upright CIRT provided dose distributions with target dose coverage and OAR dose sparing equivalent to those of the conventional supine CIRT. Upright CIRT for prostate cancer is expected to have equivalent treatment effectiveness while offering reduced installation costs and simple system management of platforms.

PMID:
42440346
Bibliographic data and abstract were imported from PubMed on 13 Jul 2026.

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