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Comparative Study
. 2016 Apr 1;34(10):1043-9.
doi: 10.1200/JCO.2015.62.1383. Epub 2016 Jan 25.

Comparing Intelligence Quotient Change After Treatment With Proton Versus Photon Radiation Therapy for Pediatric Brain Tumors

Lisa S Kahalley  1 , M Douglas Ris  2 , David R Grosshans  2 , M Fatih Okcu  2 , Arnold C Paulino  2 , Murali Chintagumpala  2 , Bartlett D Moore  2 , Danielle Guffey  2 , Charles G Minard  2 , Heather H Stancel  2 , Anita Mahajan  2
Affiliations
Comparative Study

Comparing Intelligence Quotient Change After Treatment With Proton Versus Photon Radiation Therapy for Pediatric Brain Tumors

Lisa S Kahalley et al. J Clin Oncol. .

Abstract

Purpose: Compared with photon radiation (XRT), proton beam radiation therapy (PBRT) reduces dose to normal tissues, which may lead to better neurocognitive outcomes. We compared change in intelligence quotient (IQ) over time in pediatric patients with brain tumors treated with PBRT versus XRT.

Patients and methods: IQ scores were available for 150 patients (60 had received XRT, 90 had received PBRT). Linear mixed models examined change in IQ over time since radiation therapy (RT) by RT group, controlling for demographic/clinical characteristics. Craniospinal and focal RT subgroups were also examined.

Results: In the PBRT group, no change in IQ over time was identified (P = .130), whereas in the XRT group, IQ declined by 1.1 points per year (P = .004). IQ slopes did not differ between groups (P = .509). IQ was lower in the XRT group (by 8.7 points) versus the PBRT group (P = .011). In the craniospinal subgroup, IQ remained stable in both the PBRT (P = .203) and XRT groups (P = .060), and IQ slopes did not differ (P = .890). IQ was lower in the XRT group (by 12.5 points) versus the PBRT group (P = .004). In the focal subgroup, IQ scores remained stable in the PBRT group (P = .401) but declined significantly in the XRT group by 1.57 points per year (P = .026). IQ slopes did not differ between groups (P = .342).

Conclusion: PBRT was not associated with IQ decline or impairment, yet IQ slopes did not differ between the PBRT and XRT groups. It remains unclear if PBRT results in clinically meaningful cognitive sparing that significantly exceeds that of modern XRT protocols. Additional long-term data are needed to fully understand the neurocognitive impact of PBRT in survivors of pediatric brain tumors.

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Conflict of interest statement

Authors’ disclosures of potential conflicts of interest are found in the article online at www.jco.org. Author contributions are found at the end of this article.

Figures

Fig 1.
Fig 1.
Bold lines represent the regression lines of IQ change over time since RT for each RT group, on the basis of average values for all variables included in the model (Table 2). Fine lines represent unadjusted change in IQ over time for individual patients. IQ, intelligence quotient; PBRT, proton beam radiation therapy; RT, radiation therapy; XRT, photon radiation therapy.
Fig 2.
Fig 2.
Regression lines of IQ change over time since RT for each RT group and by CSI/focal RT history, on the basis of average values for all variables included in the model (Tables 3 and 4). CSI, craniospinal irradiation; IQ, intelligence quotient; PBRT, proton beam radiation therapy; RT, radiation therapy; XRT, photon radiation therapy.
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References

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