Abstract
Purpose: To evaluate the performance of the hippocampal normal tissue complication model that relates dose to the bilateral hippocampus to memory impairment at 18 months post-treatment in a population of low-grade glioma (LGG) patients.Methods: LGG patients treated within the radiotherapy-only arm of the EORTC 22033-26033 trial were analyzed. Hippocampal dose parameters were calculated from the original radiotherapy plans. Difference in Rey Verbal Auditory Learning test delayed recall (AVLT-DR) performance pre-and 18 (±4) months post-treatment was compared to reference data from the Maastricht Aging study. The NTCP model published by Gondi et al. was applied to the dosimetric data and model predictions were compared to actual neurocognitive outcome.Results: A total of 29 patients met inclusion criteria. Mean dose in EQD2 Gy to the bilateral hippocampus was 39.8 Gy (95% CI 34.3–44.4 Gy), the median dose to 40% of the bilateral hippocampus was 47.2 EQD2 Gy. The model predicted a risk of memory impairment exceeding 99% in 22 patients. However, only seven patients were found to have a significant decline in AVLT-dr score.Conclusions: In this dataset of only LGG patients treated with radiotherapy the hippocampus NTCP model did not perform as expected to predict cognitive decline based on dose to 40% of the bilateral hippocampus. Caution should be taken when extrapolating this model outside of the range of dose-volume parameters in which it was developed.
Highlights
Low grade glioma (LGG) are a group of relatively slow growing primary brain neoplasms, mainly occurring in those between 30 and 50 years of age [1, 2]
With many LGG patients living for many years or even decades after treatment, the late adverse effects of treatment on quality of life and neurocognitive functioning are of increasing importance
In addition to evaluating the performance of the NTCP model, we investigated if Clinical target volume (CTV) volume, laterality, age, handedness, and WHO performance score were associated with cognitive deterioration
Summary
Low grade glioma (LGG) are a group of relatively slow growing primary brain neoplasms, mainly occurring in those between 30 and 50 years of age [1, 2]. With many LGG patients living for many years or even decades after treatment, the late adverse effects of treatment on quality of life and neurocognitive functioning are of increasing importance. Both the tumor itself, as well as the use of anticonvulsant therapy, have a deleterious effect on neurocognitive function [5, 6], radiotherapy (RT) in particular has been associated with a negative impact on neurocognitive function. This late effect of radiotherapy was found in several series with a longer follow-up [7, 8], it was not found in several studies that limited observation to the first 5 years [9,10,11,12]
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