Table 2.
Linear Mixed Effects Model of IQ Change Over Time by RT Group (n = 123)*
| Parameter | Beta† | 95% CI | P |
|---|---|---|---|
| Time since RT, years | −0.7 | −1.6 to 0.2 | .130 |
| RT group (XRT) × time since RT, years | −0.4 | −1.6 to 0.8 | .509 |
| RT group, XRT | −8.7 | −15.5 to −2.0 | .011 |
| Age at RT, years | −0.1 | −0.9 to 0.8 | .905 |
| Total RT dose to tumor, Gy | −0.1 | −0.9 to 0.7 | .810 |
| CSI | 4.7 | −6.5 to 15.8 | .414 |
| VP shunt | −4.7 | −10.9 to 1.6 | .144 |
| Tumor location, supratentorial‡ | −1.3 | −10.2 to 7.7 | .778 |
| Tumor diameter, cm‡ | −1.3 | −3.5 to 0.8 | .227 |
| Histology | .276 | ||
| Glioma | — | ||
| Medulloblastoma/PNET | −7.7 | −21.4 to 6.0 | .271 |
| Ependymoma | 7.3 | −6.9 to 21.6 | .312 |
| Germ cell tumor | −2.6 | −16.7 to 11.5 | .716 |
| Other§ | 5.7 | −5.2 to 16.5 | .306 |
| Performance score ≤ 80‡║ | −6.7 | −13.9 to 0.4 | .063 |
| SES‡ | −18.3 | −46.1 to 9.5 | .197 |
| Race/ethnicityঠ| .146 | ||
| White | — | ||
| Black | −10.2 | −19.0 to -1.4 | .023# |
| Hispanic/Latino | −2.2 | −10.1 to 5.6 | .579 |
| Other | 0.5 | −11.0 to 12.0 | .935 |
| IQ test type | .000 | ||
| Leiter | — | ||
| Woodcock-Johnson | 12.1 | 5.2 to 19.1 | .001 |
| Wechsler | 2.1 | −3.6 to 7.8 | .465 |
Abbreviations: —, reference group; CSI, craniospinal irradiation; IQ, intelligence quotient; PNET, primitive neuroectodermal tumor; RT, radiation therapy; SES, socioeconomic status; VP, ventriculoperitoneal; XRT, photon radiation therapy.
Twenty-seven patients were excluded from the model because of missing data on covariates.
Beta = slope.
Data were missing for tumor location (n = 2), tumor diameter (n = 7), performance score (n = 15), SES (n = 1), and race (n = 3).
Other histology category includes craniopharyngioma (n = 13), choroid plexus carcinoma (n = 4), meningioma (n = 2), ganglioneuroblastoma (n = 1), neuronal glial (n = 1), epidermoid (n = 1), and undetermined (n = 1).
║Performance score was obtained from the Lansky/Karnofsky rating at the first clinic visit after diagnosis.
Other race category includes Asian (n = 8) and American Indian (n = 2).
Because the overall effect for race/ethnicity was not significant, the significant result for the black versus white contrast is not interpreted as a significant effect.