The incidence of radiation-induced moyamoya among pediatric brain tumor patients who received photon radiation versus those who received proton beam therapy: a systematic review.

Cranial irradiation is associated with several adverse events such as endocrinopathy, growth retardation, neurocognitive impairment, secondary malignancies, cerebral vasculopathy, and potential stroke. The better side effects profile of proton beam therapy compared with that of photon radiation therapy is due to its physical properties, mainly the sharp dose fall-off after energy deposition in the Bragg peak. Despite the better toxicity profile of proton beam therapy, the risk of  moyamoya syndrome still exists. We conducted a systematic review of the existing literature on moyamoya syndrome after receiving cranial radiation therapy for pediatric brain tumors to investigate the incidence of moyamoya syndrome after receiving photon versus proton radiation therapy. In this review, we report that the incidence of moyamoya syndrome after receiving proton beam therapy is almost double that of photon-induced moyamoya syndrome. Patients who received proton beam therapy for the management of pediatric brain tumors are more likely to develop moyamoya syndrome at the age of less than 5 years. Meanwhile, most patients with proton-induced moyamoya are more likely to be diagnosed within the first 2 years after the completion of their proton beam therapy.