Overview
This prospective, single-center study will evaluate the feasibility, spatial stability, and dosimetric effects of an absorbable hydrogel spacer placed between the cervix/vagina and rectum before definitive radiotherapy for cervical cancer. Approximately 30 participants will receive hydrogel spacer implantation before the first fraction of external beam radiotherapy (EBRT), followed by standard definitive radiotherapy including EBRT and image-guided brachytherapy (IGBT).
Serial magnetic resonance imaging (MRI) and computed tomography (CT) will be used to assess spacer position, thickness, and stability throughout treatment. Radiation doses to the rectum and other organs at risk will be evaluated across the full course of radiotherapy. The primary objective is to assess the effect of the hydrogel spacer on cumulative rectal dose while maintaining adequate target coverage. Procedure-related safety and feasibility will also be evaluated.
Description
This is a prospective, single-center, single-arm exploratory study enrolling approximately 30 participants with cervical cancer who are scheduled to receive definitive radiotherapy. An absorbable hydrogel spacer will be implanted between the posterior cervix/vaginal wall and the anterior rectal wall before the first fraction of EBRT. The spacer procedure is performed in addition to standard oncologic treatment and does not otherwise alter the planned definitive radiotherapy or systemic therapy.
Participants will undergo longitudinal imaging to characterize the spacer throughout the course of treatment. Baseline imaging will be obtained before implantation (T0). Post-implantation MRI and planning CT will be performed at T1, followed by mid-course MRI during EBRT (T2), routine MRI before brachytherapy (T3), and follow-up MRI approximately 1 month after completion of radiotherapy (T4). Spacer thickness, volume, morphology, position, and displacement will be assessed over time.
Dosimetric analyses will evaluate the rectum and other organs at risk during both EBRT and IGBT. The primary endpoint is the cumulative rectal D2cc expressed as equivalent dose in 2-Gy fractions (EQD2) across the full course of radiotherapy. Target coverage and additional dose-volume parameters for the rectum, bladder, sigmoid colon, and small bowel will also be evaluated.
For EBRT, paired pre-spacer and post-spacer planning datasets will be used to evaluate changes in organ-at-risk dose under comparable planning conditions. Exploratory comparisons may also be performed using matched historical controls treated without hydrogel spacer implantation. Technical feasibility, procedure-related adverse events, spacer stability, and longitudinal imaging characteristics will be assessed as secondary or exploratory outcomes.
Eligibility
Inclusion Criteria:
- Female participants aged 18 to 75 years.
- Pathologically confirmed cervical cancer planned for definitive external beam radiotherapy combined with brachytherapy.
- Previously untreated disease with no prior pelvic radiotherapy.
- Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 and considered by the investigator to be able to complete definitive radiotherapy.
- Able to undergo pelvic magnetic resonance imaging (MRI) and other imaging examinations required by the study before treatment.
- Anatomical conditions considered suitable by imaging and investigator assessment for hydrogel spacer implantation between the posterior cervix/vaginal wall and the anterior rectal wall.
- Able to understand the study, willing to participate, and able to provide written informed consent.
Exclusion Criteria:
- Prior pelvic radiotherapy or other prior radiotherapy considered likely to substantially affect dosimetric evaluation in this study.
- Pregnancy or breastfeeding.
- Active pelvic infection, fever, or other acute condition making an invasive procedure unsuitable.
- Rectovaginal fistula, obvious rectal wall invasion, severe rectal inflammation, or other conditions considered by the investigator to substantially increase the risk of rectal perforation or fistula associated with spacer implantation.
- Severe coagulation abnormality or an uncorrectable bleeding risk.
- Severe cardiac, pulmonary, hepatic, renal, or other systemic disease considered by the investigator to prevent completion of treatment or study follow-up.
- Known history of severe allergy to components of the study product.
- Any other condition that, in the investigator's judgment, makes the participant unsuitable for the study.
