Therapeutic schedules influence the pattern of intellectual decline after irradiation of posterior fossa tumors.

Background: To evaluate intellectual decline in children with posterior fossa (PF) tumors treated with different therapeutic protocols.

Procedure: Forty children had a complete neuropsychological evaluation prospectively twice, at least 6 months year (y) after the end of their treatment. Patients were classified into four groups according to treatment schedules: Group 1 (n = 7) PF radiotherapy (PFRT) alone at 50 Gy; Group 2 (n = 13) reduced-dose cranio-spinal irradiation (CSI) at 25 Gy with a PF boost; Group 3 (n = 9) standard CSI at 35 Gy and a PF boost; and Group 4 (n = 11) high-dose chemotherapy with stem cell support followed by PFRT at 50 Gy.

Results: At the first evaluation (mean interval since diagnosis 3.7 y), the mean Full-Scale Intellectual Quotient (FSIQ) was 80 (SD = 19). Only patients in Group 1 had a normal mean IQ score of 92 (SD = 14). At the second evaluation (mean interval since diagnosis 6.3 y), the mean FSIQ scores were significantly lower with a mean difference of 2.4 points, i.e., a yearly decline of one point. The magnitude of the FSIQ decline was positively correlated with the first IQ score (P = 0.0001) and inversely correlated with age at diagnosis (P = 0.0005). A FSIQ decline was observed in all treatment groups except Group 1 (P = 0.005). The differences in FSIQ observed initially between the four treatment groups persisted at the second evaluation.

Conclusions: This study shows that FSIQ continues to decline more than 4 years after the diagnosis but this yearly decline seems to decrease with time from diagnosis. Therapeutic schedules influence the magnitude of this decline. Long-term follow-up into adulthood is necessary to effectively adapt patient rehabilitation.