Gonadal-sparing total body irradiation with the use of helical tomotherapy for nonmalignant indications

Abstract

background: the aim was to demonstrate the feasibility and technique of gonadal sparing total body irradiation (tBi) with helical tomotherapy. total body irradiation is a common part of the conditioning regimen prior to allogeneic stem cell transplantation. Shielding or dose-reduction to the gonads is often desired to preserve fertility, particularly in young patients undergoing transplant for non-malignant indications. helical tomotherapy (ht) has been shown to be superior to traditional tBi delivery for organ at risk (oaR) doses and dose homogeneity. Materials and methods:We present two representative cases (one male and one female) to illustrate the feasibility of this technique, each of whom received 3Gy in a single fraction prior to allogeneic stem cell transplant for benign indications. the planning target volume (PtV) included the whole body with a subtraction of oaRs including the lungs, heart, and brain (each contracted by 1cm) as well as the gonads (testicles expanded by 5 cm and ovaries expanded by 0.5 cm). results: For the male patient we achieved a homogeneity index of 1.35 with a maximum and median planned dose to the testes of 0.53 Gy and 0.35 Gy, respectively. in-vivo dosimetry demonstrated an actual received dose of 0.48 Gy. For the female patient we achieved a homogeneity index of 1.13 with a maximum and median planned dose to the ovaries of 1.66 Gy and 0.86 Gy, respectively. conclusion: Gonadal sparing tBi is feasible and deliverable using ht in patients with non-malignant diseases requiring tBi as part of a pre-stem cell transplant conditioning regimen.

Dosimetric Evaluation of the Uterus in Patients Receiving Total Body Irradiation with Ovarian Shielding

“…In this study, the uterine dose was reduced to 7–7.6 Gy, suggesting that uterine dose reduction does not affect the course of pregnancy and delivery for patients who received TBI with ovarian shielding after puberty. Recent advances in TBI using intensity-modulated radiation therapy have enabled the radiation dose to the reproductive organs to be reduced to the idealized dose [ 18 ]. As more and more TBI using intensity-modulated radiation therapeutic techniques are expected to be performed in the future, further studies with a larger number of patients are warranted to determine the radiation dose to the reproductive organs to maintain normal pregnancy and childbearing processes in female survivors who have undergone TBI.…”

Preservation of male fertility in patients undergoing pelvic irradiation

“…Compared to a conformal 3D plan, modulated treatments (such as IMRT and VMAT) require the utilization of more MUs and are therefore less efficient in delivering the prescription dose, which consequently results in proportional increases in collimator scatter and head leakage [ 50 ]. However, if flattening-filter-free (FFF) beams are used, MUs will increase but gantry head leakage will decrease owing to the absence of the flattening filter, a major contributor to head leakage [ 52 ]. With the exception of neutron contribution, out-of-field doses vary little with beam energy or depth in the patient, except at the patient’s surface near the field edge [ 50 ].…”

“…With the exception of neutron contribution, out-of-field doses vary little with beam energy or depth in the patient, except at the patient’s surface near the field edge [ 50 ]. Dibs et al demonstrated meaningful gonadal sparing with the use of helical tomotherapy for patients undergoing total body irradiation for nonmalignant indications [ 52 ].…”