Tc-99m MIBI uptake and its relation to the proliferative potential of brain tumors

Purpose: Many studies have shown that the S-phase fraction is a reflection of the proliferation potential of tumors, and DNA aneuploidy is more common in malignant tumors. In this preliminary study, the authors assessed the Tc-99m MIBI uptake of brain tumors and its relation to tumor grade and DNA content of the tumor cells. Methods: Ten patients (eight male, two female; mean age, 53.2 +/- 6.11 years) with untreated brain tumors were included in the study. SPECT imaging was performed 20 minutes after injection of 740 MBq (20 mCi) Tc-99m MIBI. A single detector camera with a low-energy high-resolution collimator was used for image acquisition. A region of interest was drawn in the tumor area under magnetic resonance guidance. A Tc-99m MIBI uptake index was computed as the mean tumor-to-background ratio. Flow cytometric analysis of fresh tumor tissue specimens was performed immediately. The percentages of cells in the G0/G1, S, and G2/M phases were determined for each patient. Results: DNA aneuploidy was found in 4 (49%) patients, whereas diploidy was found in 6 (60%) patients. There was a significant positive correlation between the Tc-99m MIBI uptake and the percentage of the S-phase fraction of the cell cycle (P = 0.000, r = 0.95). The Tc-99m MIBI index was significantly greater in aneuploid tumors than in diploid tumors (P < 0.01). Conclusions: High-grade brain tumors have increased Tc-99m MIBI uptake compared with that of low-grade tumors. Tc-99m MIBI uptake is correlated with the percentage of the S-phase fraction of the cell and the aneuploidy level of the brain tumor. This preliminary report suggests that Tc-99m MIBI imaging may be useful in the evaluation of the biologic characteristics of brain tumors.