Dose dependent cerebellar atrophy in glioma patients after radio(chemo)therapy

Background and purpose:

Radiotherapy is a standard treatment option for high-grade gliomas. Cognitive impairment is a side effect associated with radiotherapy particularly in long-term survivors. Recent findings suggest involvement of the cerebellum in cognitive function. The goal of this study was therefore to investigate dose dependent cerebellar atrophy using prospective, longitudinal MR data from adult glioma patients who received radiotherapy.
Materials and methods:
Cerebellar volumes were measured using T1-weighted MR images from 91 glioma patients before radiotherapy and every three months thereafter. We calculated the average cerebellar volume change per year per Gy, based on the mean cerebellar dose, using linear regression analysis. Subsequently, patient age was investigated as a confounding factor using multiple linear regression analysis. The impact of chemotherapy was assessed separately in a subgroup of patients receiving a cerebellar dose ≤ 1 Gy. Cerebellar mean dose and cerebellar volume changes were compared between patients treated with proton (N = 38) and photon therapy (N = 52).
Results:
Cerebellar volume decreased 2.4 % per 10 Gy per year (p < 0.001). The cerebellar volume loss was progressive over time without signs of recovery within the observational period of two years. Neither patient age (p = 0.27) nor chemotherapy (p = 0.43) had a significant impact on cerebellar atrophy. Compared to patients treated with photons, the cerebellar dose was significantly lower in patients treated with proton therapy (p < 0.001, r = 0.62) which also translated to a significantly lower cerebellar volume reduction per year (p = 0.016, r = 0.25).
Conclusion:
Cerebellar volume decreased significantly and irreversibly after radiotherapy as function of time and dose. Further work is now needed to correlate these results with cognitive function and motor performance.