Prognostic significance of imaging contrast enhancement for WHO grade II gliomas

Abstract

In this study, we investigated the prognostic value of MRI contrast enhancement (CE) at the time of histological diagnosis specifically in a selected population of WHO grade II gliomas. We reviewed 927 histologically proven WHO grade II gliomas for which contrast-enhanced MR images were available at the time of histological diagnosis. CE patterns were classified into three categories: "patchy and faint," "nodular-like," and "ring-like." CE progression over time was recorded before oncological treatment on successive MR images, when available. CE was present in 143 cases (15.9%), with 93 patchy and faint, 50 nodular-like, and no ring-like patterns. CE areas were time progressive before oncological treatment in 35 of the 56 available cases (62.5%). Regardless of its pattern, the presence of CE was not significantly associated with a worsened prognosis (p = 0.415) by univariate analysis. Only the nodular-like pattern of CE (p < 0.01) and the time-progressive CE (p < 0.001) in the available subgroup proved to be statistically associated with survival since first oncological treatment. The present results show the necessity, in cases of WHO grade II gliomas, to study CE at the time of histological diagnosis and, whenever possible, to follow its progression over time before oncological treatment. Nodular-like CE and time-progressive CE are associated with a worsened prognosis, both suggesting malignant transformation, even though histopathological examination cannot initially disclose signs of malignancy in those areas.

Fig. 1

Example of biopsy sampling performed on the area of contrast enhancement. Axial T1-weighted sequences before (left) and after (right) injection of gadopentetate dimeglumine showing a small nodular-like contrast enhancement at the time of histological diagnosis (A) and after biopsy sampling (B). This case was taken from the gliomas under study.

Fig. 2

Examples of MRI patterns of contrast enhancement on axial T1-weighted sequence before (left) and after (right) injection of gado -pentetate dimeglumine. (A and B) Patchy and faint pattern of contrast enhancement. (C and D) Nodular-like pattern of contrast enhancement. (E and F) Ring-like pattern of contrast enhancement. A–D were taken from the gliomas under study; E and F were taken from a high-grade glioma library.

Fig. 3

Examples of MRI time-progressive contrast enhancement before oncological treatment on axial T1-weighted sequence after injection of gadopentetate dimeglumine. (A) Time-progressive contrast enhancement at 2-month interval. (B) Time-progressive contrast enhancement at 3-month interval. A and B were both taken from the gliomas under study.

Fig. 4

Kaplan-Meier estimates of survival since first oncological treatment by contrast enhancement (CE) pattern: absent, patchy and faint, or nodular-like.