MRS of oligodendroglial tumors - Correlation with histopathology and genetic subtypes

Background: Oligodendroglial neoplasms with combined loss of chromosomes 1p and 19q may have a good prognosis and respond to procarbazine-lomustine (CCNU)- vincristine (PCV) chemotherapy. Objective: To determine whether single voxel magnetic resonance spectroscopy (SV- MRS) obtained through routine clinical practice distinguishes between histopathologic and genetic subtypes of oligodendroglial tumors. Methods: Forty- eight patients with oligodendroglial tumors (19 oligodendrogliomas and 29 oligoastrocytomas) underwent molecular genetic analysis to determine allelic imbalance in chromosomes 1p36 and 19q13. SV- MRS was obtained pretherapy to determine tumor metabolite ratios. Results: Grade III oligodendroglial tumors had higher choline (Mann - Whitney; p = 0.002), methyl lipid (Mann - Whitney; p = 0.002), and combined methylene lipid and lactate ratios (Mann - Whitney; p < 0.001) than grade II tumors. Lactate did not distinguish between tumor types (Fisher exact test; p = 0.342) or grade (Fisher exact test; p = 0.452). There were no significant associations when tumors were analyzed according to histopathology or genetic subtypes. Conclusion: As a noninvasive diagnostic tool used in routine clinical practice, SV- MRS has the potential benefit of determining oligodendroglial tumor grade but not subtypes classified by histopathology or molecular genetics. MRS may be useful for determining the timing of therapy but is unlikely to predict chemosensitivity.