Influence of volumetric modulated arc therapy and FET-PET scanning on treatment outcomes for glioblastoma patients

Background: We sought to assess the influence of the clinical introduction of new radiotherapy technologies on glioblastoma patients’ outcomes. Methods: Newly diagnosed glioblastoma patients treated with 60 Gy and temozolomide (2005–2014) were analyzed. The patients’ GTV and CTV were defined based on MR (n = 521) or FET-PET/MR (n = 190), and were treated using conformal radiotherapy (CRT, n = 159) or image-guided volumetric modulated arc therapy with hippocampal sparing (IG-VMAT, n = 362). Progression-free survival (PFS) was assessed using the McDonald criteria. Associations between clinical data, dosimetry data, treatment technology, for PFS and overall survival (OS) were explored. Results: The PFS (7 months) and OS (15 months) were unaffected by CRT, IG-VMAT and FET-PET technology. Mean brain dose was correlated with tumor volume, and was lower for IG-VMAT vs. CRT (p < 0.001). Larger mean brain dose was associated with inferior PFS (univariate/multivariate Cox models, p < 0.001) and OS (univariate, p < 0.001). Multivariate Cox models revealed association of larger mean brainstem dose (p < 0.001), BTV (p = 0.045), steroid use at baseline (p = 0.003), age (p = 0.019) and MGMT status (p = 0.022) with lower OS. Conclusions: Introduction of hippocampal-sparing IG-VMAT technology appeared to be safe, and may have reduced toxicity and cognitive impairment. Larger mean brain dose was strongly associated with inferior PFS and OS.