Injectable bio-absorbable spacers in brachytherapy for gynecological cancers: A scoping review

Purpose: Insertion of a spacer between tumor and an adjacent organ at risk may improve the therapeutic ratio in gynecological cancer brachytherapy. The purpose of this review was to assess the available literature on the use of injectable bio-absorbable spacers in brachytherapy for gynecological cancers. Material and methods: Embase, PubMed, Medline, and Cochrane Central Register of Controlled Trials were searched until March 28, 2024. Studies reporting on injectable bio-absorbable spacers in gynecological cancer brachytherapy were included. Two independent reviewers completed screening, assessment for eligibility, and data extraction of included studies. Data were collected on spacer material, technique, safety, feasibility, spacer quality, dosimetric values, clinical outcomes, and cost-effectiveness. Results: Seventeen studies met inclusion criteria, with a total of 312 patients and 169 spacers. Clinical application was primarily in cervix cancer brachytherapy (47%) and spacer placement in the recto-vaginal space (88%). Eight dif-ferent products were used, with no significant spacer-related adverse effects reported. Spacer insertion reduced rectal dose in eight studies, bladder dose in one study, sigmoid dose in four studies, and permitted tumor dose escalation in three studies. Five studies reported on tumor outcomes and eight studies on late toxicities. There were no studies evaluating patient-reported outcomes and cost-effectiveness. Conclusions: Injectable bio-absorbable spacers offer a promising approach for improving the therapeutic ratio in gynecological cancer brachytherapy. There is low certainty evidence available in the literature for their use, and rigor-ous prospective studies are needed to provide evidence on outcomes.