RTHP-15. NEURAL STEM CELL NICHE INVOLVEMENT AND PATTERNS OF FAILURE IN GLIOBLASTOMA MULTIFORME

Abstract

To evaluate the impact of magnetic resonance imaging (MRI) dynamics of glioblastoma, in context of pre and post treatment involvement of the neural stem cell compartment (NSC) on progression free (PFS) and overall survival (OS). Baseline and followup MRI images were serially evaluated in 61 patients treated with standard post resection chemoradiation and temozolomide between 2011 to 2015. MRI morphology groups were based on any combination(s) of NSC involvement, cortical involvement or both by contrast enhancing lesions (CELs). MRI images at recurrence were registered with the radiation treatment planning datasets in order to assess the patterns of failure in context of the previously contoured NSC volumes. With a median followup of 14.1 months (interquartile range 9.4 – 20.6 months), the median [95% confidence interval (CI)] PFS and OS were 14.5 (95% CI 11.6 – 17.5 months) and 16.2 (95% CI 13.3 – 19.2 months) months, respectively. Baseline involvement of NSC with CELs with varying degrees of cortical involvement was seen in 41/61 patients. At progression, 95.9% patients had progressive involvement of previously contoured NSC with CELs and FLAIR abnormalities. In patients with CELs involving the NSC at presentation, log-rank univariate analyses revealed a non significant decline in PFS (13.01 vs 15.18 months, p = 0.51) and OS (14.62 vs 17.08 months, p = 0.62). However, there was a significantly higher chance of distant brain progression (40.5%, p = 0.05) and multifocal progression (36%, p = 0.05) in patients with pretreatment NSC involvement with CELs compared to those without. In our cohort, pre treatment NSC involvement was associated with a significantly higher incidence of distant brain failure and multifocal recurrences. Though it did not reach significance, baseline NSC involvement might be associated with inferior PFS and OS. Prospective validation in a larger cohort is necessary.