ESTRO 2025 - Abstract Book

S2769

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2025

Material/Methods:

We derived ovarian doses from radiation treatment planning data in pediatric CT images of 50 patients aged 5–16 years. We created VMAT and IMPT treatment plans with clinical target volumes (CTVs) defined up to S3 to mitigate asymmetric growth due to rapid dose gradients in patients with immature skeletal structures. A 23.4 Gy dose was prescribed to cover ≥99% of the CTV. We then performed multiple regression analysis to develop a predictive model for ovarian doses. The explanatory variables were set as the bladder and small- and large-bowel volumes. A total of 49 cases were used for model development. One case was used for testing with five cross-validations. The risk calculator based on female childhood cancer survivor data from the St. Jude lifetime cohort was used to estimate the ovarian insufficiency risk.

Results:

The mean absolute error results from comparing the planned max dose and the predicted dose were 0.95 ± 0.72 Gy in the VMAT and 0.70 ± 0.11 Gy in IMPT plans, respectively, enabled accurate ovarian dose predictions for both irradiation methods. The estimated mean ovarian insufficiency risks for patients ≤40 years old were 20% in VMAT and 15% in IMPT for CSI, which gave significant reductions in the fertility risk. Conclusion: We developed a predictive model for the primary ovarian insufficiency risk based on the treatment planning dose and the bladder and bowel volumes in pediatric patients with CSI. The expected exposure dose and ovarian insufficiency risk from our predictive models were assumed in subsequent VAMT and IMPT.

Keywords: Primary ovarian insufficiency risk, CSI, Predict