18F-FET PET for planning of thermotherapy using magnetic nanoparticles in recurrent glioblastoma

Purpose: Thermotherapy using magnetic nanoparticles (nano cancer therapy) is a new concept of local tumour therapy, which is based on controlled heating of intra-tumoural injected magnetic nanoparticles. The aim of this study was to evaluate the usefulness of PET with a recently introduced amino acid tracer O-(2-[F-18] fluoroethyl)-L-tyrosine (FET) for targeting the nanoparticles implantation. Materials and methods: Eleven patients with glioblastoma recurrences underwent MR and FET-PET imaging for planning of the nano cancer therapy. Thereafter, the gross tumour volumes (GTV) were defined, taking into consideration the results of both imaging tools. Results: The MRI-based mean GTV was 24.3cm(3) (range 2.5-59.7) and the PET-based mean GTV 31.9cm(3) (range 5.2-77.9). On the average the MRI identified an additional 8.9 +/- 4.7cm(3) and the FET-PET scan-an additional 16.5 +/- 15.2cm(3) outside of the common GTV (15.4 +/- 11.0cm(3)). The mean final GTV accounted to 33.8cm(3) (range, 5.2-77.9). The additional information of FET-PET led to an increase in GTV by 22-286% in eight patients and to a decrease of 23% and 26%, respectively, in two patients. In one patient, the final GTV was defined on the basis of MRI data only. Conclusions: FET-PET adds important information on the actual tumour volume in recurrent glioblastomas and is highly valuable for defining the target volume for the nano cancer therapy.