Objective:

We sought to define the
time to first progression in MGMT methylated glioblastoma patients who were
treated with standard of care/Stupp protocol (this has not been previously defined).

Background:

MGMT methylated glioblastomas respond well to standard of care with
temozolomide, have a longer survival as well as increased risk of pseudo-progression
as compared to unmethylated patients. Shorter survival in these patients despite
effective treatments is due to misdiagnosis of true progression (in cases with
pseudo-progression) that leads to overtreatment or discontinuation of effective
treatments. There are limited non-invasive diagnostic tools to distinguish true
progression from pseudo-progression. Knowing the expected time to first true
progression will aid with interpretation of MRI changes and serve as an additional
tool to distinguish true from pseudo-progression.

Design/Methods:

We conducted a retrospective analysis of an IRB-approved database at our
institution from 2019 to 2022 of all MGMT methylated glioblastoma patients who
completed Stupp protocol. Time to first progression (time from initial surgery to first
true progression) was determined by treating multidisciplinary team based on
radiographic review +/- pathology. Eligible MGMT methylated glioblastoma patients
had IDH status determined by NGS and completed standard Stupp protocol after
surgery.

Results:

Approximately 30% (27) patients with IDH wild-type glioblastoma
were MGMT methylated. 10 patients met eligibility criteria. 50% of MGMT
methylated GBM patients had multifocal disease at presentation. Median time to
first progression in MGMT methylated GBM who received standard of care was 28
months. 20% patients have not had first progression 3 years after initial surgery.

Conclusions:

MRI changes on surveillance scans should be carefully interpreted in the
first 28 months. Knowing time to first true progression will aid with management
decisions and decrease unnecessary early aggressive interventions in MGMT
methylated glioblastoma patients. We will validate these findings in a larger patient
population at our institution.