11C-methionine positron emission tomography for target delineation of recurrent glioblastoma in re-irradiation planning

Publication date: May–June 2018
Source:Reports of Practical Oncology & Radiotherapy, Volume 23, Issue 3
Author(s): Hidekazu Tanaka, Takahiro Yamaguchi, Kae Hachiya, Kazuhiro Miwa, Jun Shinoda, Masahide Hayashi, Shinichi Ogawa, Hironori Nishibori, Satoshi Goshima, Masayuki Matsuo
AimTo define the optimal margin on MRI scans in the re-radiation planning of recurrent glioblastoma using methionine positron emission tomography (MET-PET).BackgroundIt would be very useful if the optimal margin on MRI to cover the uptake area on MET-PET is known.Materials and MethodsCT, MRI, and MET-PET were performed separately over the course of 2 weeks. Among the MRI scans, we used the contrast-enhanced T1-weighted images (Gd-MRI) and T2-weighted images (T2-MRI). The Gd-MRI-based clinical target volume (CTV) (CTV-Gd) and the T2-MRI-based CTV (CTV-T2) were defined as the contrast-enhanced area on Gd-MRI and the high intensity area on T2-MRI, respectively. We defined CTV x mm (x=5, 10, 15, 20) as x mm outside the CTV. MET-PET-based CTV (CTV-MPET) was defined as the area of accumulation of MET-PET. We calculated the sensitivity and specificity of CTV-Gd and CTV-T2 following comparison with CTV-MPET, which served as the gold standard in this study.ResultsThe sensitivity of CTV-T2 5mm (98%) was significantly higher than CTV-T2 (87%), and there was no significant difference in the sensitivity between CTV-T2 5mm and CTV T2 10, 15, or 20mm. The sensitivity of CTV-Gd 20mm (97%) was lower than that of CTV-T2 5mm (98%).ConclusionsA margin of at least 5mm around the high intensity area on T2-MRI is necessary in the target volume delineation of recurrent glioblastoma for the coverage of MET-PET findings in re-radiation therapy planning.



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