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.