Performance of Standardized Relative CBV for Quantifying Regional Histologic Tumor Burden in Recurrent High-Grade Glioma: Comparison against Normalized Relative CBV Using Image-Localized Stereotactic Biopsies

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Fig 1.
FTB maps in 3 separate biopsy cases correlating with low, medium, and high histologic tumor content. The 3 rows correspond to 3 separate patients and 3 separate biopsy locations, as shown by the green square ROIs on the anatomic postcontrast images in the far-left column (1A, 1B, 1C). The middle and far right columns show the biopsy locations (green square ROIs) in relation to the normalized (Norm) FTB (1B, 2B, 3B) and standardized (Std) FTB (1C, 2C, 3C) maps. On the FTB maps, blue corresponds to predicted PTRE regions with low rCBV ≤1.0. The yellow (1.75 ≥ rCBV >1.0) and red (rCBV >1.75) correspond to predicted tumor regions. For this study, FTB was defined as the percentage of both yellow and red voxels relative to all voxels within an ROI.
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Fig 2.
ROC analyses of the top-performing rCBV metrics for predicting ≥ 50% histologic tumor content (A) and ≥ 80% histologic tumor content (B). A, ROC curve for predicting ≥50% histologic tumor content using normalized (blue curve) and standardized (red dotted curve) median rCBV. B, ROC curve for predicting ≥80% histologic tumor content using normalized (blue curve) and standardized (red dotted curve) FTB. The standardized metrics show similar performance compared with corresponding normalized metrics.

Table 1:

Patient demographics and distribution of recurrent tumors by pathology and grade

	Total No.	Age (yr)	Men (Total)	Women (Total)
Patient demographics	38	Mean = 49.3, Range = 24–69	19	19
Pathology and grade
Recurrent ODG (GIII)	3	Mean = 46	2	1
Recurrent astrocytoma (GIII)	2	Mean = 52	1	1
Recurrent GBM (GIV)	33	Mean = 50	16	17

Note:—ODG indicates oligodendroglioma; GIII, WHO Grade III; GIV, WHO Grade IV.

Table 2:

Summary of predictive performance for normalized and standardized rCBV metrics

rCBV Metric	Histologic Tumor Content (0%–100%), Pearson Coefficient (P Value)	Tumor Content ≥50%, ROC-AUC (Optimal Threshold)	Tumor Content ≥80%, ROC-AUC (Optimal Threshold)

FTB
Normalized	r = 0.63 (<.001)	0.80 (0.72)	0.77 (0.84)
Standardized	r = 0.66 (<.001)	0.82 (0.56)	0.80 (0.64)
Mean rCBV
Normalized	r = 0.45 (<.001)	0.86 (1.558)	0.75 (1.603)
Standardized	r = 0.53 (<.001)	0.85 (1.187)	0.78 (1.187)
Median rCBV
Normalized	r = 0.48 (<.001)	0.87 (1.68)	0.77 (1.378)
Standardized	r = 0.55 (<.001)	0.86 (1.071)	0.79 (1.10)