Long-term intellectual outcome in children with posterior fossa tumors according to radiation doses and volumes.

Objective: To analyze the relationship between craniospinal irradiation (CSI) and intellectual outcome in children with posterior fossa (PF) tumors.

Methods: A neuropsychological evaluation was performed retrospectively in 31 children, aged 5-15 years, who had received radiotherapy for PF tumors, and who had been off therapy for at least 1 year. Factors evaluated for impact on intellectual outcome were: socioeconomic status, disease presentation, histology, complications, chemotherapy, age at radiotherapy, interval between radiotherapy and testing, and radiation doses and volumes. Patients were divided into 3 subgroups according to the CSI doses (0 Gy [i.e., PF irradiation only], 25 Gy, and 35 Gy), with 11, 11, and 9 patients, respectively.

Results: Long-term cognitive impairment occurred in most of the patients, even after PF irradiation only. Moreover, there was a significant correlation between the full-scale IQ score (FSIQ) and the CSI dose, with mean FSIQ scores at 84.5 (SD = 14.0), 76.9 (SD = 16.6), and 63.7 (SD = 15.4) for 0 Gy, 25 Gy, and 35 Gy of CS1, respectively. A marked drop in verbal comprehension scores was noted in children who had received the higher dose.

Conclusions: This preliminary study further supports the rationale for de-escalation of CSI doses and volumes in standard-risk PF tumors.