Preoperative growth dynamics of untreated glioblastoma – Description of an exponential growth-type, correlating factors and association with postoperative survival

Little is known about growth dynamics of untreated glioblastoma and its possible influence on postoperative survival. Our aim was to analyze a possible association of preoperative growth dynamics with postoperative survival. We performed a retrospective analysis of all adult patients surgically treated for newly diagnosed glioblastoma at our center between 2010 and 2020. By volumetric analysis of data of patients with availability of ≥3 preoperative sequential MRI, a growth pattern was aimed to be identified. Main inclusion criterion for further analysis was the availability of two preoperative MRI scans with a slice thickness of 1mm, at least 7 days apart. Individual growth rates were calculated. Association with overall survival (OS) was examined multivariably. Out of 749 patients screened, thirteen had ≥3 preoperative MRI, 70 had two MRI and met the inclusion criteria. A curve estimation regression model showed best fit for exponential tumor growth. Median tumor volume doubling time (VDT) was 31 days, median specific growth rate (SGR) was 2.2% growth per day. SGR showed negative correlation with tumor size (rho=-0.59, p<0.001). Growth rates were dichotomized according to the median SGR.OS was significantly longer in the group with slow growth (log rank: p=0.010). Slower preoperative growth was independently associated with longer overall survival in a multivariable Cox-regression model for patients after tumor resection. Especially small lesions suggestive for glioblastoma showed exponential tumor growth with variable growth rates and a median VDT of 31 days. SGR was significantly associated with OS in patients with tumor resection in our sample.