ESTRO 2025 - Abstract Book

S1625

Clinical – äediatric tumours

ESTRO 2025

Material/Methods: The study obtained ethical approval (21-10088-BO) from the local Ethics Committee. Clinical and dosimetric data was available from a prospective registry (DRKS00005363). Endocrine evaluation was performed at the affiliated endocrinology department before and regularly after PBT allowing retrospective assessment of growth hormone status from laboratory values and provocation tests. Patients with pre-irradiation GHD were excluded for this analysis. Cumulative incidence of GHD since start of PBT was estimated using Kaplan-Meier method. In subgroup analysis, dose thresholds of 20 Gy D mean to the hypothalamus [1, 2] and 30 Gy D mean to the pituitary [3, 4] were evaluated. Log rank testing was used to detected differences between dose groups. Results: Data of 42 children (boys/girls 19/23) with a median age at RT of 7.8 years (range, 1.7-17.6 years) treated between 2013-2021 was evaluable. The cohort consisted of different CNS/base of skull tumours. Median total dose was 54 Gy RBE (range, 18-74 Gy RBE ). Nine patients (21.4%) received craniospinal irradiation with a cranial boost. Median D mean to the hypothalamus and to the pituitary was 40.1 Gy RBE (range, 0.0-59.3 Gy RBE ) and 40.4 Gy RBE (range, 0.5-66.0 Gy RBE ), respectively (Figure 1).

The median endocrine follow up (FU) time was 3.6 years (range, 0.6-8.7 years). 15 patients (35.7%) experienced GHD after a median of 1.2 years (range, 0.5-5.7 years). The 1-, 2- and 3-years CI of GHD was 9.5%±4.5%, 28.1%±7.3% and 36.3%±0.8%. D mean to the hypothalamus and pituitary was ≤ 20 Gy RBE , and/or ≤ 30 Gy RBE , respectively, in 11 patients, and > 20 Gy RBE , and/or > 30 Gy RBE , respectively, in 31 patients. GHD was only observed in the group with doses above threshold, whereas no one in the group below threshold, developed GHD (p=.004; Figure 2).