Background: In this study several tumor-related volumes were assessed by means of a computer-based\r\napplication and a survival analysis was conducted to evaluate the prognostic significance of pre- and postoperative\r\nvolumetric data in patients harboring glioblastomas. In addition, MGMT (O6-methylguanine methyltransferase)\r\nrelated parameters were compared with those of volumetry in order to observe possible relevance of this molecule\r\nin tumor development.\r\nMethods: We prospectively analyzed 65 patients suffering from glioblastoma (GBM) who underwent radiotherapy\r\nwith concomitant adjuvant temozolomide. For the purpose of volumetry T1 and T2-weighted magnetic resonance\r\n(MR) sequences were used, acquired both pre- and postoperatively (pre-radiochemotherapy). The volumes\r\nmeasured on preoperative MR images were necrosis, enhancing tumor and edema (including the tumor) and on\r\npostoperative ones, net-enhancing tumor. Age, sex, performance status (PS) and type of operation were also\r\nincluded in the multivariate analysis. MGMT was assessed for promoter methylation with Multiplex Ligationdependent\r\nProbe Amplification (MLPA), for RNA expression with real time PCR, and for protein expression with\r\nimmunohistochemistry in a total of 44 cases with available histologic material.\r\nResults: In the multivariate analysis a negative impact was shown for pre-radiochemotherapy net-enhancing tumor\r\non the overall survival (OS) (p = 0.023) and for preoperative necrosis on progression-free survival (PFS) (p = 0.030).\r\nFurthermore, the multivariate analysis confirmed the importance of PS in PFS and OS of patients. MGMT promoter\r\nmethylation was observed in 13/23 (43.5%) evaluable tumors; complete methylation was observed in 3/13\r\nmethylated tumors only. High rate of MGMT protein positivity (> 20% positive neoplastic nuclei) was inversely\r\nassociated with pre-operative tumor necrosis (p = 0.021).\r\nConclusions: Our findings implicate that volumetric parameters may have a significant role in the prognosis of\r\nGBM patients. Furthermore, volumetry could help not only to improve the prediction of outcome but also the\r\noutcome itself by identifying patients at high risk of treatment failure and, thus, seek alternative treatment for these\r\npatients. In this small series, MGMT protein was associated with less aggressive tumor characteristics.
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