Spacer in Gynaecological MRI-guided brachytherapy: A feasibility study

Insertion of hyaluronic acid gel spacer (Barrigel) into the rectovaginal space in participants with in situ gynaecological cancer treated with high dose rate brachytherapy. Barrigel is used as a rectal spacer in prostate cancer radiation therapy but has had limited use in gynaecological cancers. Hyaluronic acid gel spacer insertion: The first brachytherapy session will proceed as per standard of care without spacer and will act as a control to explore the secondary outcome of dosimetric comparison. Insertion of the hyaluronic acid spacer will occur with the second fraction of brachytherapy, however, due to resource limitations including personnel, theatre time and relevant equipment, this may not be feasible and may occur with a different fraction. Spacer insertion will occur at the institution operating theatre under general (or spinal) anaesthesia, approximately 10-30 minutes prior to gynaecological brachytherapy applicator insertion. The radiation oncologist will inject Barrigel transvaginally or transperineally into the rectovaginal space under transrectal ultrasound guidance to increase the space between the rectum and gynaecological target (cervix and/or vagina). The volume injected will be at the discretion of the radiation oncologist based on individual anatomy. The radiation oncologist will insert the brachytherapy applicator immediately after spacer insertion and the participant will then continue with standard MRI-guided brachytherapy processes per institution protocol. There will only be one spacer insertion for the entire brachytherapy course which may comprise of 3-4 brachytherapy sessions. Additional MRI scans (imaging only without brachytherapy) will be performed at 3 months and 12 months to assess for presence of the gel and characteristics.