Study population:
27 patients with recurrent GBM were selected from the local database for the period from 2012 to 2018 and enrolled in the retrospective study.
The recurrence was proven either with surgical biopsy or MRI surveillance.
Prior to the relapse event all patients undergone gross tumor resection and received Intensity Modulated radiation therapy (IMRT) combined with concurrent or adjuvant temozolomide as a primary treatment of high-grade Glioblastoma.
Data acquisition:
MR spectroscopy (MRS) and apparent diffusion coefficient (ADC) parameters of pretreatment (baseline) diagnostic studies were analyzed for their potential to predict early recurrence.
All patients MRI data was obtained on 1.5 Tesla scanner by using extended brain protocol: T2-WI,
FLAIR,
T1-WI,
T1CE, DW-images (b-values of 0,
50,
200,
500,
800 and 1000 s/mm2) and pre-contrast ADC maps (automatically calculated from the b=0 and b=1000 s/mm2 DWI series),
MR spectroscopy.
There are two basic techniques utilized in MR spectroscopy: single voxel techniques and multi-voxel techniques.
In our study we used multi-voxel imaging,
also known as CSI (chemical shift imaging) and MRSI (MR spectroscopic imaging).
This technique allows obtain spectra from a large volume of interest (VOI) and CSI is better suited for evaluation of larger size glioblastomas.
It also allows for comparison and normalization of pathologic spectra to spectra in normal tissue.
To provide information about metabolites intermediate TE (135 to 144 ms) was chosen.
Data was recorded for peaks Lip+Lac,
Cho+nCho,
NAA and Cr and was used to calculate the ratios.
Apparent diffusion coefficient (ADC) parameter is known for correlation with GBM cellularity.
ADC measurements are taken at the regions of contrast enhanced areas and compared to normal brain tissue of the similar region in the contralateral hemisphere.
ADCmean and ADCmax in regions of interest were delineated manually on axial images.
The normalized ADC ratio was calculated.
Therapy\surgery data:
In this study all patients underwent gross tumor resection and received combination of intensity-modulated radiotherapy (IMRT) with concurrent chemotherapy treatment with temozolomide (TMZ).
During the radiotherapy course 60 Gy were administered for gross tumor eradication; the delineated gross tumor volume (GTV) had an isotropic expansion of 20 mm for the clinical target volume (CTV).
Statistical analysis:
IBM SPSS Statistics 24 (SPSS Inc.,
Chicago,
IL,
USA) was used for statistical analysis.
Descriptive statistics were expressed as numbers and percentages for categorical variables and mean with range for continuous variables.
Fisher’s exact test and the nonparametric Mann-Whitney U test were used with continuous and noncontinuous variables to establish any differences between the subgroups of early and late recurrence.
Two-tailed P values less than 0.05 were considered to indicate a significant difference.