Dosimetric impacts on height development after radiotherapy for intracranial non-germinomatous germ cell tumors.

Objectives: Intracranial non-germinomatous germ cell tumors (NGGCTs) are rare pediatric central nervous system (CNS) tumors. Growth impairment induced by radiation treatment was rarely evaluated. We aimed to evaluate the impacts of radiotherapy on height development as well as the dosimetric constraints, providing potential insights for hormonal replacement treatment.

Methods: A total of 128 pediatric patients diagnosed with NGGCTs were retrospectively studied. Sex, age at irradiation, physical doses and biologically effective dose (BED), height and endocrine status were obtained for analysis. The cumulative change in height was assessed using age-matched normalized height (ANH). Cumulative physical doses and BEDs for the whole brain and pituitary were derived via dose-volume histograms (DVHs) and BED-volume histograms (BEDVHs).

Results: For pediatric patients ≤ 11.5 years, linear correlations between ANH and cumulative physical doses as well as BEDs to the whole brain and pituitary were identified. More specifically, dosimetric constraints to the pituitary were 36 Gy for physical dose (AUC = 0.70 [95% CI, 0.54-0.86], p < .05) and 63 Gy₂ BED (AUC = 0.69 [95% CI, 0.53-0.86], p < .05). Impaired hormone secretion with respect to growth hormone (GH) and thyroid-stimulating hormone (TSH) was observed following cranial irradiation (both p < .001), particularly for those with tumors at the suprasellar region (GH: p < .01, TSH: p < .001). Unlikely to patients > 11.5 years, the height development for patients with tumors in the suprasellar region was significantly more affected than those in the other locations (p < .01) among patients ≤11.5 years.

Conclusions: Our study revealed the impacts of cumulative doses and tumor locations for radiation-associated growth impairment. Reduced levels of GH and TSH were observed in patients ≤ 11.5 years particularly with tumors in the suprasellar region.