The role of MRI in patients with astrocytoma WHO II treated with fractionated stereotactic radiotherapy

Progressive Low-Grade Glioma: Assessment of Prognostic Importance of Histologic Reassessment and MRI Findings

BACKGROUND

In patients with progressive low-grade glioma (LGG), the presence of new magnetic resonance imaging (MRI) enhancement is commonly used as an indicator of malignant degeneration, but its accuracy in this setting is uncertain.

OBJECTIVE

We characterize the ability of new MRI enhancement to serve as a surrogate for histologic grade in patients with progressive LGG, and to explore the prognostic value of new MRI enhancement, pathologic grade, and extent of resection.

METHODS

Patients at our institution with World Health Organization grade II glioma diagnosed between 1994 and 2010 and who underwent repeat biopsy or resection at progression were retrospectively reviewed (n = 108). The positive predictive value, negative predictive value, sensitivity, and specificity of new MRI enhancement were characterized. A multivariable proportional hazards model was used to test associations with overall survival (OS), and Kaplan-Meier curves were constructed to compare OS between patient subsets.

RESULTS

The positive predictive value, negative predictive value, sensitivity, and specificity of new MRI enhancement were 82%, 77%, 92%, and 57%, respectively. In patients without malignant degeneration, new MRI enhancement was associated with inferior median OS (92.5 months vs. not reached; P = 0.03). In patients with malignant degeneration, gross or near total resection was associated with improved median OS (58.8 vs. 28.8 months; P = 0.02).

CONCLUSION

In patients with progressive LGG, new MRI enhancement and pathologic grade were discordant in greater than 20% of cases. Pathologic confirmation of grade should therefore be attempted, when safe, to dictate management. Beyond functioning as a surrogate for pathologic grade, new MRI enhancement may predict for worse outcomes, a concept that merits prospective investigation.

Prognostic significance of imaging contrast enhancement for WHO grade II gliomas

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.

Genetic aberrations in gliomatosis cerebri

OBJECTIVE

Identifying the genetic alterations in gliomatosis cerebri (GC) may yield clinically useful prognostic markers and provide clues as to whether GC represents a distinct pathological entity or is an extreme form of diffusely infiltrative glioma.

METHODS

Clinical histories, treatment histories, magnetic resonance imaging, and pathological analysis of patients with GC treated at either the University of California San Francisco or the Mayo Clinic were reviewed. Degenerate oligonucleotide-primed polymerase chain reaction was performed on biopsy samples of GC. Comparative genomic hybridization was used to determine relative deoxyribonucleic acid copy number. We evaluated relationships of clinical and radiological treatment and comparative genomic hybridization data to survival after diagnosis with Cox regression analysis.

RESULTS

Radiographic analysis and biopsy specimens were available for study in 29 patients (17 men, 12 women). Comparative genomic hybridization was successfully performed in 22 patients. Contrast enhancement was the most significant predictor of poor survival (P = 0.0026). Loss of chromosomes 13q and 10q and gains of 7q were also independent significant predictors of poor survival (P = 0.0032, 0.0335, and 0.0487, respectively). Patients treated with temozolomide or with radiation therapy had improved survival, but this effect did not reach statistical significance (P = 0.180 and 0.124, respectively).

CONCLUSION

Chromosomal aberrations associated with aggressive astrocytomas are predictors of poor outcome in patients with GC. This suggests that GC may be an architectural variant of diffuse astrocytomas. The presence of these aberrations and the presence of any contrast enhancement on magnetic resonance imaging scans are possible stratifiers for patients with GC. Stratification of GC into higher- and lower-grade forms may be useful in tailoring treatments to patients with this disease.

MR-Perfusions- und spektroskopische Bildgebung bei WHO-Grad-II-Astrozytomen

BACKGROUND

This study evaluates whether MR perfusion imaging and spectroscopic imaging (MRSI) can depict anaplastic areas in WHO grade II astrocytomas, whether these areas are co-localized, and whether the prognosis can be better predicted.

MATERIAL AND METHODS

Fifteen patients (nine female, six male, aged 42+/-14 years) with WHO grade II astrocytomas but without preceding radio- or chemotherapy were examined every 3 months with MR perfusion imaging and MRSI (mean follow-up 18 months). Using a region of interest analysis, the regional relative cerebral blood volume (rrCBV) and blood flow (rrCBF) were measured in tumor tissue. In the same areas, choline/creatine (Cho/Cr) and choline/N-acetyl-aspartate (Cho/NAA) ratios were quantified.

RESULTS

During follow-up, nine patients had stable disease. In six patients, the tumor showed progression and contrast-enhancement. The progressing tumors had already had higher perfusion (rrCBF 2.1+/-1.4; rrCBV 1.9+/-1.1) parameters than the stable astrocytomas (rrCBF 1.2+/-0.6, p=0.01; rrCBV 1.4+/-0.8, p=0.05) at first examination. However, the Cho/NAA and Cho/Cr ratios only tended to be higher than in stable astrocytomas (Cho/NAA 2.4+/-1.0 vs. 2.0+/-1.5, p=0.23; Cho/Cr 1.7+/-0.6 vs. 1.4+/-0.5, p=0.06). In all six progressing tumors, areas of maximum perfusion and maximum Cho/NAA and Cho/Cr ratio were co-localized. During follow-up, contrast-enhancement was observed in these areas.

CONCLUSIONS

MR perfusion imaging can depict anaplastic areas in WHO grade II astrocytomas earlier than conventional MRI and thus enables a better prediction of prognosis.

Follow-up gliomas after radiotherapy: 1H MR spectroscopic imaging for increasing diagnostic accuracy

We evaluated the value of magnetic resonance imaging (MRI) and the additional benefit of proton MR spectroscopic imaging (1H SI) in patients with a new suspicious lesion after fractionated stereotactic radiotherapy (FSRT) of a glioma. Thirty-four patients with histologically proven astrocytoma WHO II-IV after treatment by FSRT and a new suspect lesion in the follow-up were included in this study. Data were analysed by three independent radiologists with different experience in 1H SI: Data were verified by clinical follow-up (PT, progressive tumour; nPT, non-progressive tumour) and a kappa analysis was performed. Sensitivity and specificity of T1 weighted (w) and T2w MRI was compared (imaging at radiotherapy and follow-up) using further follow-up controls as gold standard and the additional benefit of 1H SI (imaging at follow-up) was calculated. Mean interval between last irradiation and detection of a suspicious lesion was 37 +/- 32 months. Time to clinical evaluation was 13 +/- 8 months. Interobserver agreement was significantly high in all analyses (kappa always >0.8, P < 0.05). T2w imaging proved to be superior to contrast enhanced T1w imaging in sensitivity (87.5 vs 81.25%) and specificity (85.7 vs 57.1%). Solitary 1H SI had similar results as T2w (sensitivity 87.5%, specificity 71.4%). Taking all techniques into account, all PT were correctly diagnosed. Radiologists' experience had no significant influence on correct interpretation of a suspicious lesion. We conclude that 1H SI is helpful in characterising new suspicious lesions in irradiated gliomas, particularly if pre-MRI is not available for evaluating follow-up.