ASCO 2013：脑肿瘤患者行光子放疗会降低IQ

IQ change within three years of radiation therapy in pediatric brain tumor patients treated with proton beam radiation therapy versus photon radiation therapy
Background
Radiation therapy (RT), an essential treatment for pediatric brain tumors, increases the risk of cognitive impairment. Advanced RT techniques reduce the volume of normal tissues receiving radiation dose. Proton beam radiation therapy (PBRT) minimizes irradiation to surrounding healthy brain tissue, with the potential to preserve cognitive function better than photon radiotherapy (XRT). We examined change in IQ over time between patients treated for pediatric brain tumors with PBRT versus XRT.
Methods
IQ scores obtained in the first 3 years post-RT were abstracted for pediatric brain tumor patients treated with PBRT or XRT.
Results
Baseline and follow-up IQ scores were available for 53 survivors (31 PBRT, 22 CRT). A linear regression model predicted follow-up IQ scores controlling for baseline IQ, age-at-RT, time-since-RT, and craniospinal irradiation (CSI), F(7,45)=23.4, p<.001. Follow-up IQ scores were significantly lower in the XRT group compared to the PBRT group (p<.05). The XRT group lost 10.3 IQ points on average with each additional year post-RT (p<.01), while the PBRT group remained stable, losing only 0.1 points per year on average (p<.05). CSI was associated with IQ decline in both groups (p<.05), while age-at-RT was not in either group (p=.154). Total RT dose was not associated with IQ with the above variables in the model.
Conclusions
Findings suggest significant cognitive risk is associated with XRT, with IQ scores declining by more than half a standard deviation with each additional year post-RT. In contrast, IQ remained stable in the PBRT group. Preliminary findings suggest that PBRT may spare cognitive functioning in the first 3 years post-RT. Future research should replicate these findings with a larger sample and should study longer-term cognitive outcomes in patients treated with PBRT versus XRT.