Volumetry of [11C]-methionine PET uptake and MRI contrast enhancement in patients with recurrent glioblastoma multiforme

We investigated the relationship between three-dimensional volumetric data of the metabolically active tumour volume assessed using [C-11]-methionine positron emission tomography (MET-PET) and the area of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) enhancement assessed using magnetic resonance imaging (MRI) in patients with recurrent glioblastoma (GBM). MET-PET and contrast-enhanced MRI with Gd-DTPA were performed in 12 uniformly pretreated patients with recurrent GBM. To calculate the volumes in cubic centimetres, a threshold-based volume-of-interest (VOI) analysis of the metabolically active tumour volume (MET uptake indexes of a parts per thousand yen1.3 and a parts per thousand yen1.5) and of the area of Gd-DTPA enhancement was performed after coregistration of all images. In all patients, the metabolically active tumour volume as shown using a MET uptake index of a parts per thousand yen1.3 was larger than the volume of Gd-DTPA enhancement (30.2 +/- 22.4 vs. 13.7 +/- 10.6 cm(3); p = 0.04). Metabolically active tumour volumes as shown using MET uptake indexes of a parts per thousand yen1.3 and a parts per thousand yen1.5 and the volumes of Gd-DTPA enhancement showed a positive correlation (r = 0.76, p = 0.003, for an index of a parts per thousand yen1.3, and r = 0.74, p = 0.005, for an index of a parts per thousand yen1.5). The present data suggest that in patients with recurrent GBM the metabolically active tumour volume may be substantially underestimated by Gd-DTPA enhancement. The findings support the notion that complementary information derived from MET uptake and Gd-DTPA enhancement may be helpful in developing individualized, patient-tailored therapy strategies in patients with recurrent GBM.