Comparison of mutation in isocitrate dehydrogenase-1 gene with conventional MRG and MR spectroscopy findings in brain tumors

Purpose: In this study, it will be investigated whether there is a significant difference between Conventional MR findings and MR Spectroscopy metabolites Cho/Cr and Cho/NAA ratios in IDH1-mutant and IDH1-wild type cases. At the same time, if the correlation between Conventional MRI and MR Spectroscopy findings of IDH1-mutant and IDH1-wild type cases can be demonstrated, it is aimed to be used as an auxiliary method in determining the treatment protocol. Materials and Methods: Our study included 24 cases with histopathologically confirmed diagnosis of primary brain tumor and IDH1 mutation status between January 2020 and December 2022 and pre-postoperatively MR Spectroscopy. It was investigated whether there was a significant difference between conventional MRI findings of IDH1 mutant and wild type cases and Cho/Cr and Cho/NAA metabolites. Results: Thirteen (54.2%) of the 24 participants included in the study were male and 11 (45.8%) were female. Histopathological examination results of 17 patients were glioblastoma (70.8%), 6 patients had astrocytoma (25%), 1 patient had It was a medullablostoma (4.2%). It was seen that 6 of the patients were IDH1 positive (25%) and 18 of them were IDH1 wild type (75%). As a result of histopathological examination of the tumor, WHO Grade 1 and 2 were considered low grade, WHO Grade 3 and 4 were considered high grade (We did not have WHO grade 1 cases in our study group). The presence of the tumor in a single lobe was considered unilateral, and the presence of the tumor in more than one lobe or in the opposite hemisphere was considered bilateral. Contrast enhancement of the total volume of solid tissue belonging to the tumor of 50% or less was accepted as no or moderate enhancement, and enhancement of more than 50% was considered to be significantly enhanced. When the tumor tissue compresses the surrounding structures and creates a shift of at least 5 mm in the midline, the mass effect is considered to be severe, and when there is no compression effect on the surrounding structures or if it creates less than 5 mm shift in the midline, the mass effect is considered absent or moderate. It was accepted that the peripheral vasogenic edema of the tumor was limited to the lobe where the tumor was localized or was absent, and the edema was absent or moderate, and if it was located in more than one lobe or in the opposite hemisphere, the edema was considered significant. According to the imaging features of the tumor on MRI, those considered to be malignant were considered high grade, and those considered benign were considered low grade. In the MR spectroscopy examination of 24 cases, the ratios of Cho/Cr and Cho/NAA metabolites were compared according to the histopathological grade of the tumor, growth pattern, tumor margins, signal intensity, contrast enhancement, mass effect, peripheral vasogenic edema of the tumor, conventional appearance (benign or malignant) characteristics. In the comparative analysis, no statistically significant difference was found between the Cho/Cr and Cho/NAA ratios and the characteristics of the tumor (p>0.05). The histopathological grade, growth pattern, tumor margins, signal intensity, contrast enhancement, mass effect, tumor-related peripheral vasogenic edema, conventional appearance (benign or malignant), Cho/Cr and Cho/NAA metabolites ratios of 6 IDH1 mutant and 18 IDH1 wild-type cases comparison was made. There was no statistically significant difference between the two case groups in terms of other MRI findings (p>0.05). Cho/NAA ratios of IDH1 wild type cases were significantly higher than IDH1 mutant cases. The optimal cut-off value determined to distinguish the Cho/NAA ratios between IDH1 wild-type cases and IDH1 mutant cases was determined as 1.15. Conclusions: Our study showed that Cho/NAA ratios of IDH1 wild-type cases were significantly higher than IDH1 mutant cases. Thus, we concluded that Cho/NAA ratio in MR Spectroscopy allows noninvasive differentiation of IDH1 wild-type gliomas from IDH1 mutant gliomas.