OS06.6.A FLAIR-SIGNAL INTENSITY CHANGE AS A PREDICTOR OF PROGRESSIVE GLIOBLASTOMA IN THE EORTC CENTRIC AND CORE STUDIES

Abstract

Abstract BACKGROUND In patients with glioblastoma, radiological recurrence of enhancing tissue after chemoradiotherapy can originate from progressive disease (PD) or pseudoprogression/treatment-associated changes. In earlier studies, a change of the FLAIR-signal intensity (SI) predicted PD with 18-84% sensitivity and 71-100% specificity, both with quantitative resection cavity to ventricle SI ratio of 7.3. We assessed the rate of FLAIR-signal intensity change in patients with O6-methylguanine DNA methyltransferase (MGMT) promoter-methylated or -unmethylated glioblastoma from the randomised CENTRIC and CORE studies (NCT00689221, NCT00813943). These patients were treated with chemoradiotherapy or chemoradiotherapy with cilengitide, an integrin inhibitor. METHODS Patients from both studies with a gross total resection and ≥3 follow-up MRIs were included. The outcome was determined by the modified RANO criteria of 2017. Two researchers evaluated the FLAIR-SI of the resection cavity. A positive SI change was scored qualitatively in case of a visually brighter signal intensity than on the previous MRI. Quantitative analysis was based on a ratio of SI in the resection cavity compared to SI of the ventricles. RESULTS Follow-up was available for 307 patients. Median time from RT to (preliminary) progressive disease was 6.2 months for MGMT promoter-methylated (interquartile range, (iqr)=2.5-14.7) and 6.0 for MGMT promoter-unmethylated glioblastoma (iqr=2.7-8.9). Of the 307 patients, 142 patients showed stable disease, response, or treatment-associated changes and 165 (preliminary) PD at the end of follow-up. A qualitative FLAIR-SI change was found in 61 patients (19.9%) and 44 of these developed (preliminary) PD, with a positive predictive value of 72.1% (95%-CI 59.2-82.9%); positive predictive value was 88.9% for MGMT promoter-unmethylated and 67.4% for MGMT promoter-methylated glioblastoma. We found an overall sensitivity of the FLAIR-SI-change for PD of 26.7% (95%-CI 20.1-34.1%), with ranges of 22.9 to 39.2% depending on MGMT promoter methylation status and treatment allocation; specificity ranged from 88 to 91.3%, with an overall specificity of 88.0% (95%-CI 81.5-92.9%). Median time from first FLAIR-SI to progression was 0 months (iqr=0-2.7) with a range of 0 to 13, and from the brightest signal was 0 months (iqr=0-1.0). The average signal intensity ratio was 10.2 at the time of the brightest signal; further quantitative analyses will be presented. CONCLUSION We confirmed the positive predictive value of a change in FLAIR-signal intensity of the resection cavity for concurrent or subsequent progressive disease in resected glioblastoma. Patients with such a change of the signal intensity should be worked up further on (e.g. PET imaging, biopsy, any clinical change) or else undergo another MRI closely.