Preliminary Feasibility and Dosimetric Evaluation of Retroperitoneal Hydrogel Spacer Placement for Stereotactic Body Radiation Therapy: A Cadaveric Study

@article{tanabe2026preliminary,
  title = {{Preliminary Feasibility and Dosimetric Evaluation of Retroperitoneal Hydrogel Spacer Placement for Stereotactic Body Radiation Therapy: A Cadaveric Study}},
  author = {Shin Tanabe and Kotaro Yoshio and Takaaki Komiyama and Soichi Sugiyama and Toshiya Kameoka and Ryota Kimura and Takahiro Kawabata and Yuta Otsuka and Hideki Aoyama and Kenta Watanabe and Ayano Kawaguchi and Takao Hiraki},
  journal = {Advances in Radiation Oncology},
  year = {2026},
  month = sep,
  doi = {10.1016/j.adro.2026.102211},
  url = {https://doi.org/10.1016/j.adro.2026.102211},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Preliminary Feasibility and Dosimetric Evaluation of Retroperitoneal Hydrogel Spacer Placement for Stereotactic Body Radiation Therapy: A Cadaveric Study
AU  - Shin Tanabe
AU  - Kotaro Yoshio
AU  - Takaaki Komiyama
AU  - Soichi Sugiyama
AU  - Toshiya Kameoka
AU  - Ryota Kimura
AU  - Takahiro Kawabata
AU  - Yuta Otsuka
AU  - Hideki Aoyama
AU  - Kenta Watanabe
AU  - Ayano Kawaguchi
AU  - Takao Hiraki
PY  - 2026
DA  - 2026/09/12
JO  - Advances in Radiation Oncology
DO  - 10.1016/j.adro.2026.102211
UR  - https://doi.org/10.1016/j.adro.2026.102211
AB  - Purpose: Hydrogel spacers reduce the rectal radiation dose and toxicity in prostate cancer radiation therapy. However, their use in other malignancies, including renal cell carcinoma (RCC), remains underexplored. This study aimed to explore the feasibility of hydrogel spacer placement at different retroperitoneal sites and its potential dosimetric effects during stereotactic body radiation therapy for RCC using cadaveric models.  Methods and Materials: Hydrogel spacers were percutaneously administered under computed tomography (CT) guidance to 3 cadavers at the following retroperitoneal sites: (1) the perirenal space, (2) the perivascular region of the iliac vessels, and (3) the iliacus muscle region. Spacer stability and separation distance from organs at risk were evaluated using CT images acquired immediately after placement, at 1 week, and at 1 to 2 months. The dosimetric effect was assessed in the perirenal spacer case by comparing radiation treatment plans for a simulated RCC lesion generated before and after spacer placement using a treatment planning system.  Results: Hydrogel spacer placement in the perirenal space achieved a stable separation of approximately 1 cm between the kidney and bowel, which was maintained at the 1-month follow-up. The perivascular spacer failed to maintain its shape at the time of placement and became indistinguishable on the follow-up CT, whereas the iliacus muscle spacer remained stable but provided limited bowel separation. Treatment planning showed a reduction in bowel dose in the perirenal case, with the maximum dose to the small intestine reduced by 9.6% and to the large intestine by 35.9%.  Conclusions: This exploratory cadaveric study suggests that CT-guided hydrogel spacer placement in the perirenal space may be technically feasible and may reduce the bowel dose in simulated RCC stereotactic body radiation therapy. However, the other retroperitoneal locations evaluated in this study showed less favorable spacer behavior or limited bowel separation. Further studies are required to validate these preliminary findings.
SN  - 2452-1094
ER  -