Exploring the Relationship Between Radiation-Induced Moya Moya Syndrome and Radiation Dose for Pediatric Patients Treated with Proton Radiation Therapy: Moya Moya in Peds Patients After Proton RT.

Purpose: The incidence and risk factors associated with radiation-induced Moya-Moya Syndrome (RIMMS) in pediatric brain tumor patients treated with proton radiotherapy (PRT) remain poorly understood. The objective of this study was to determine the incidence of RIMMS in the setting of CNS proton radiotherapy (PRT) in a pediatric cohort and assess its relationship with dose to the Circle of Willis (COW) or optic chiasm (OC).

Methods & materials: We performed a retrospective review of pediatric brain tumor patient treated with intracranial PRT (1995-2021). The exposure of interest was mean dose to the optic chiasm due to close proximity to the COW vasculature. Wilcoxon rank-sum test was used to determine the association between OC dose and RIMMS. Univariable logistic regression modeling was used to determine the odds of developing RIMMS based on a cutpoint of 52Gy.

Results: Of 676 patients, 14 developed RIMMS, with a median onset of 1.9 years. The cumulative incidence of RIMMS at 8 years was 2.4%. Patients with RIMMS had higher mean OC dose than those without (51.5 Gy vs 23.7 Gy, p<0.0001). Univariable logistic regression showed patients with an OC dose > 52 Gy had increased RIMMS risk compared to those with dose < 52 Gy (OR = 9.9, p<0.001).

Conclusions: The incidence of RIMMS remains low in our primarily proton-treated pediatric cohort with a cumulative incidence of 2.4% over 8 years and is similar to photon-treated cohorts. Development of RIMMS was associated with higher doses to the COW and OC.