Quantitative analysis of whole-tumor Gd enhancement histograms predicts malignant transformation in low-grade gliomas.
OBJECTIVE
To quantify subtle gadolinium (Gd) enhancement (signal increase) in whole-tumor histograms and optimize their ability to predict subsequent malignant transformation in low-grade gliomas (LGGs).


METHODS
We analyzed histograms from 21 adult subjects with LGGs (eight nontransformers and 13 transformers) who had been imaged every six months for periods of two to five years. Before transformation these tumors were reported as radiologically non-enhancing. Imaging included a T(1)-weighted volume sequence before and after a double dose of Gd-DTPA contrast agent. Image data sets were spatially registered and subtracted to obtain maps of percent enhancement (%E). Tumor outlines were defined on fluid-attenuated inversion recovery (FLAIR) images, and the volumes were calculated. Histogram tails were analyzed to obtain the volume (mL) of subtly enhancing tissue (%E > 10%).


RESULTS
Baseline enhancing volumes were higher for Ts than for NTs (P < 0.005). Kaplan-Meier survival curves for a threshold of 4 mL showed clear differences at five years (P < 0.04). Pretransformation examinations predicted transformation (corrected threshold = 3.0 mL, P = 0.011).


CONCLUSIONS
Clear histogram differences at presentation suggest that the process of transformation starts very early. It is now possible to identify individuals at high risk for transformation at baseline by quantifying the volume of subtly enhancing tumor tissue, and such findings could have an impact on patient management.
Tofts
Paul S
PS
Institute of Neurology, University College London, London, United Kingdom.
Benton
Christopher E
CE
Weil
Rimona S
RS
Tozer
Daniel J
DJ
Altmann
Daniel R
DR
Jäger
H Rolf
HR
Waldman
Adam D
AD
Rees
Jeremy H
JH
D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology*; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D005910:Glioma / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects
D003287:Contrast Media; D019786:Gadolinium DTPA