Utilizing 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) to define suspected non-enhancing tumor for radiotherapy planning of glioblastoma

Publication date: Available online 31 January 2018
Source:Practical Radiation Oncology
Author(s): Aimee R Hayes, Dasantha Jayamanne, Edward Hsiao, Geoffrey P Schembri, Dale L Bailey, Paul J Roach, Mustafa Khasraw, Allison Newey, Helen R Wheeler, Michael Back
AimTo evaluate the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiotherapy planning for patients diagnosed with glioblastoma (GBM) and presence of suspected non-enhancing tumors compared with standard magnetic resonance imaging (MRI).MethodsPatients with GBM and contrast-enhancing MRI showing regions suspicious of non-enhancing tumor underwent post-operative FET-PET prior to commencing radiotherapy. Two Clinical Target Volumes (CTVs) were created using pre- and post-operative MRI; MRI-FLAIR sequences (CTVFLAIR) and MRI contrast sequences with an expansion on the surgical cavity (CTVSx). FET-PET was used to create Biological Tumor Volumes (BTVs) by encompassing FET avid regions, forming a BTVFLAIR and BTVSx. Volumetric analyses were conducted between CTVs and respective BTVs using Wilcoxon signed-rank tests. The volume increase with addition of FET was analyzed with respect to BTVFLAIR and BTVSx. Presence of focal gadolinium contrast enhancement within previously non-enhancing tumor or within the FET avid region was noted on MRI at one and three months after radiotherapy.ResultsTwenty-six patients were identified retrospectively from our database, of which 24 had demonstrable FET uptake. The median CTVFLAIR, CTVSx, BTVFLAIR and BTVSx was 57.1 cc (range 1.1-217.4), 83.6 cc (range 27.2-275.8), 62.8 cc (range 1.1-307.3) and 94.7 cc (range 27.2-285.5) respectively. When FET-PET was utilized, there was a mean increase in volume from CTVFLAIR to BTVFLAIR by 26.8% and CTVSx to BTVSx by 20.6%. A statistically significant difference was noted on Wilcoxon signed-rank test when assessing volumetric change between CTVFLAIR and BTVFLAIR (P<0.0001) and CTVSx and BTVSx (p<0.0001). Six out of 24 patients (25%), with FET avidity prior to radiotherapy, showed focal gadolinium enhancement within the radiotherapy portal.ConclusionFET-PET may help improve delineation of GBM in cases with a suspected non-enhancing component. This may result in improved radiotherapy target delineation and reduce the risk of potential geographical miss.SummaryWe investigated the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiotherapy planning for patients diagnosed with glioblastoma (GBM) and a suspected non-enhancing tumor compared with standard magnetic resonance imaging (MRI). We performed volumetric analyses between clinical target volumes and respective biological target volumes using Wilcoxon signed-rank tests. In conclusion, FET-PET may help improve delineation of GBM in cases with a suspected non-enhancing component and reduce the risk of potential geographical miss.



http://ift.tt/2nSxd3a