Expert consensus
Brachytherapy is a special form of RT with the major advantage of having a small, circumscribed target volume compared to EBRT. Therefore, it affects less healthy tissue leading to reduced functional impairment. Application of BT needs to be adapted to the anatomy of the child. Therefore, individually adapted vaginal molds need to be created since intracavitary BT is the most common modality. Interstitial BT can be used for vulva rhabdomyosarcoma and highly infiltrating tumors may require a combination of interstitial and intracavitary brachytherapy.
When surgeons perform the vaginoscopy after 6 courses of chemotherapy to determine the presence or absence of residual tumor, biopsies or removal of any pedunculated part of the tumor without resecting the vaginal wall can be performed. This can be combined with laparoscopic temporary ovarian transposition and obtaining an impression of the vagina for a mold during the same procedure. The documentation of residual disease should initiate the planning for BT.
Prior to the initiation of BT, treatment planning should be carried out in an interdisciplinary fashion, including radiation oncologists and pediatric surgeons/urologists. Patients can be treated with either low-dose-rate (LDR), pulse-dose-rate (PDR) or high-dose-rate (HDR) BT using iridium-192 (192Ir) or other isotopes. Usually BT is administered as a total dose of 50-60 Gy (LDR and PDR) or 27.5-36 Gy (HDR) over differing timeframes. The residual disease should be considered as clinical target volume for BT but many consider the entire vaginal mucosa at risk for primary vaginal tumors. Definition of the target volume at time of BT is guided by clinical examination under general anesthesia and by any relevant imaging (most frequently MRI). Surgical clips may be placed to help identifying tumors limits on computed tomography. A vaginal impression is useful to guide catheters placement in regard to the target volumes and decrease the irradiated volume.