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. 2012 Oct;14(10):1285-93.
doi: 10.1093/neuonc/nos156. Epub 2012 Sep 6.

Survival Analysis for Apparent Diffusion Coefficient Measures in Children With Embryonal Brain Tumours

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Free PMC article

Survival Analysis for Apparent Diffusion Coefficient Measures in Children With Embryonal Brain Tumours

Matthew Grech-Sollars et al. Neuro Oncol. .
Free PMC article

Abstract

Embryonal brain tumors constitute a large and important subgroup of pediatric brain tumors. Apparent diffusion coefficient (ADC) measures have been previously used in the analysis of these tumors. We investigated a newly described ADC-derived parameter, the apparent transient coefficient in tumor (ATCT), a measure of the gradient change of ADC from the peri-tumoral edema into the tumor core, to study whether ATCT correlates with survival outcome. Sixty-one patients with histologically proven embryonal brain tumors and who had diffusion-weighted imaging (DWI) as part of their clinical imaging were enrolled in a retrospective study correlating ADC measures with survival. Kaplan-Meier survival curves were constructed for extent of surgical resection, age <3 years at diagnosis, tumor type, and metastasis at presentation. A multivariate survival analysis was performed that took into consideration ATCT and variables found to be significant in the Kaplan-Meier analysis as covariates. Results from the multivariate analysis showed that ATCT was the only significant covariate (P < .001). Survival analysis using Kaplan-Meier curves, dividing the patients into 4 groups of increasing values of ATCT, showed that more negative values of ATCT were significantly associated with a poorer prognosis (P < .001). A statistically significant difference was observed for survival data with respect to the change in ADC from edema into the tumor volume. Results show that more negative ATCT values are significantly associated with a poorer survival among children with embryonal brain tumors, irrespective of tumor type, extent of resection, age <3 years at diagnosis, and metastasis at presentation.

Figures

Fig. 1.
Fig. 1.
Measuring the ATCT: the white box in (A) indicates the area on the ADC map that is analyzed. The edema-tumor boundary is identified as marked by the white contour in (B), which also shows the white matter (WM), peri-tumoral edema (O), and tumor core (T). The ATCT is measured at 4 different locations using a 2-voxel width as shown by the voxels highlighted in black. Therefore, ATCT is measured in a total of 8 locations. The calculation for the gradient change in ADC is shown in (C) and is performed by applying a linear fit to the circled ADC values for the vertical column of 4 pixels on the left, at the posterior side of the tumor. The gradient change in ADC is measured in all 8 locations, and the mean of these is the ATCT. In the image, voxels in white represent those voxels considered for measuring the ATCO.
Fig. 2.
Fig. 2.
Plot of survival against ATCT (A), ATCO (B), mean ADC (C), and minimum ADC (D) in 58 patients. Patients who died are marked by a black box and can be seen to have a more negative ATCT value in (A). A statistically significant linear fit to the data was observed for ATCT (R = 0.49, P < .001). No significant correlation between survival and ATCO, mean ADC, and minimum ADC was observed (P = .17, P = .37, and P = .70, respectively).
Fig. 3.
Fig. 3.
Kaplan-Meier survival curves for age at diagnosis (A), extent of surgery (B), tumor type (C), and metastasis at presentation (D). Children <3 years of age are known to have a poorer prognosis, as confirmed by the survival curves, and a statistically significant P <.001. Children having had total surgical resection have a statistically significant higher chance of survival (P = .04). Tumor type and metastasis at presentation were not found to be statistically significant (P = .09 and P = .59, respectively).
Fig. 4.
Fig. 4.
Kaplan-Meier survival curves for increasingly negative values of ATCT show a decreasing survival probability (P < .001).
Fig. 5.
Fig. 5.
Visualizing the ATCT. The image visualizes the hypothetical difference between a highly negative value of ATCT (A and B) and a less negative value of ATCT (C and D). A highly negative value of ATCT means that there is an increased change in ADC from the first voxel on the edema-tumor boundary toward the tumor core. We believe this is related to either a larger change in cellularity from the first voxel toward the tumor core (A) or due to increased edema in the first voxel (B). The increasingly darker shades of grey represent the decreasing values of ADC as tumor cellularity inside the corresponding voxel increases. Conversely, the less negative value of ATCT could be due to less edema being present (C) or due to a smaller change in cellularity from the first voxel towards the tumor core (D).

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