Survival and Enhancing Fraction (enf) in Glioblastoma Multiforme (GBM)

Abstract

In GBM, enhancing fraction derived from the initial area under the contrast agent concentration curve ( IAUC ), EnF IAUC 60 , correlates with the MRI parameter K trans (contrast agent transfer coefficient). Thresholding voxels as enhancing when IAUC 60>2.5mMol.s (EnF IAUC 60>2.5 ) separates high from low grade glioma. The objectives were to evaluate the feasibility of deriving a signal intensity based enhancing fraction (EnF SI ), assess its relationship with EnF IAUC 60 measures and examine relationships with survival in GBM. 30 GBM had pre-operative pre and post-contrast T 1 -weighted imaging and a T 1 -DCE-MRI protocol. EnF IAUC 60>0 and EnF IAUC 60>2.5 were generated from IAUC 60 maps. EnF SI was derived from pre and post-contrast T1-weighted sequences. Bland/Altman plots assessed agreement between EnF measures. A multivariate Cox regression analysis examined the prognostic value of EnF measures. The mean difference between EnF IAUC 60>0 and EnF SI was 0.0378 (range -0.112-0.264, std. dev 0.07573) and between EnF IAUC 60>2.5 and EnF SI was -0.2492 (range -0.6096-0.2416, std. dev 0.2154). EnF SI demonstrated good correlation with both EnF IAUC 60>0 and EnF IAUC 60>2.5 but was not directly interchangeable with either metric. Increased EnF IAUC 60>0 was associated with prolonged survival (p=0.008). A non-significant trend was seen with EnF SI (p=0.061). EnF SI can be derived from conventional imaging and correlates with IAUC 60 based metrics. Furthermore, enhancing fraction conveys potential prognostic information in GBM.