Determination of the cutoff point of the absolute value of MGMTmRNA for predicting the therapeutic resistance to temozolomide in glioblastoma.

Background: We previously reported that the absolute value of O ⁶ -methylguanine-DNA methyltransferase (MGMT) messenger RNA (mRNA) obtained using real-time reverse transcription polymerase chain reaction (RT-PCR) might be useful for predicting both the prognosis and the results of therapy for glioblastoma (GB) treated by temozolomide (TMZ).
Methods: MGMT mRNA was measured in 55 newly diagnosed cases of GB less than 75 and had a Karnofsky performance status (KPS) of at least 60 by real-time reverse transcription polymerase chain reaction (RT-PCR) using the TaqMan probe. A receiver operating characteristic analysis was performed to determine the cutoff points for progression free survival (PFS) and overall survival (OS).
Results: In 55 patients with GB, 1200 and 3600 for PFS, 1200, 2100 and 2900 copies/μgRNA for OS were the candidate cutoff points. Significantly longer PFS and OS were observed in patients who did not exceed 1200 copies/μg RNA.
Conclusions: One thousand and two hundred copies/μg RNA appeared to be the most reasonable cutoff point of MGMTmRNA in GB for deciding to use other anti-tumor drugs such as Bevacizumab together with TMZ.