Outcomes of Image-guided High-dose-rate Uterovaginal Brachytherapy With Single Implantation

Plain-language summary

Background and Rationale: Locally advanced cervical cancer remains a major public health concern worldwide and in France. Standard-of-care management involves concurrent chemoradiotherapy followed by brachytherapy, which is critical for local tumour control and survival. Conventional high-dose-rate (HDR) brachytherapy protocols often require multiple implantations under anaesthesia, entailing increased logistical demands, operating room use, and patient discomfort. The UNICURE-HD study investigates a simplified brachytherapy approach - a single intraoperative implantation delivering all planned fractions - combined with image guidance (MRI and/or CT) and 3D dosimetry, in order to assess whether it can maintain oncological outcomes while reducing treatment complexity and resource consumption. Objectives: Primary objective: To evaluate local control at 3 and 5 years after completion of chemoradiotherapy and image-guided HDR uterovaginal brachytherapy with single implantation. Secondary objectives: To assess pelvic nodal control, para-aortic nodal control, distant control, progression-free survival, overall survival, and acute/late severe toxicities (CTCAE v5.0 ≥ grade 3). Prognostic factors will be analysed, and exploratory predictive models will be developed. Study Design: This is a retrospective, observational, multicentre study involving six French cancer centres (Pitié-Salpêtrière, Saint-Louis, Tenon, Institut de Cancérologie de Lorraine, Centre Oscar Lambret, CHU de La Réunion). Eligible patients are women ≥18 years, diagnosed with FIGO 2018 stage IB3-IV cervical cancer, treated between January 2014 and June 2024 with concurrent chemoradiotherapy followed by image-guided HDR uterovaginal brachytherapy using a single implantation. Methods: Data will be extracted from medical records (electronic or paper), pseudonymised locally, and entered into a secure AP-HP-hosted database compliant with GDPR and the MR004 framework. Variables collected include demographics, tumour characteristics, EBRT details, brachytherapy technique (endocavitary vs hybrid/interstitial), dosimetric parameters (EQD2 for HR-CTV, IR-CTV, OARs), and outcomes. Imaging protocols, applicator types, and treatment times will also be recorded. Statistical analysis will use descriptive statistics, Kaplan-Meier survival estimation, log-rank tests, and multivariable Cox regression. Predictive models (LASSO, random forests) will be explored. Analyses will be conducted in R software. Sample Size: Approximately 400 patients are expected, representing all eligible cases treated over the 10-year period in the participating centres. Ethics and Regulatory Compliance: The study follows GDPR and French data protection regulations (MR004). Ethics opinion has been requested from the Sorbonne Université Ethics Committee. Each centre will retain the correspondence table linking identifiers to pseudonyms locally; no directly identifying data will be shared. Potential Impact: If the single-implantation HDR brachytherapy strategy achieves equivalent tumour control and toxicity profiles compared to multi-implant protocols, it could streamline cervical cancer management, reduce anaesthetic risk, improve patient comfort, and optimise resource use in high-volume oncology departments. This could have significant implications for accessibility and cost-effectiveness of cervical cancer care, particularly in settings with limited resources.

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