PET studies with a Ga-68-Bombesin analogue (BZH3) for the diagnostics of brain tumors and comparison to FDG

Objectives Dynamic PET studies with a ⁶⁸Ga-Bombesin analog, the ⁶⁸Ga-BZH3, were performed in patients with suspected recurrent gliomas for diagnosis of tumor recurrence. Furthermore, dynamic ¹⁸F-Fluorodeoxyglucose (FDG) studies were performed for comparison.

Methods The ongoing study comprises 14 patients with suspected recurrent gliomas. Dynamic PET scans using ⁶⁸Ga-BZH₃ and FDG were obtained on two different days within one week. SUV´s were calculated and a compartment model (two-tissue) as well as sa non-compartment model was used for data evaluation of both tracers.

Results In 12/14 patients tumor recurrence was histologically confirmed (five pts. with a WHO II, 5 pts. with a WHO III and 4 pts. with a WHO IV). Nine pts. demonstrated an increased ⁶⁸Ga-BZH3 uptake, two of them with a WHO II, three with a WHO III and four with a WHO IV tumor. Six patients revealed an enhanced FDG metabolism, two with a WHO II, two with a WHO III and two with a WHO IV. The median values for ⁶⁸Ga-BZH3 in the recurrent tumors were: SUV 1.3, VB: 0.118, K1: 0.179, k3: 0.046. Gene chip analysis revealed an enhanced Neuromedin B expression in the evaluated tissue samples, which was correlated to an enhanced ⁶⁸Ga-BZH3 uptake.

Conclusions ⁶⁸Ga-BZH3 may be helpful in patients with suspected recurrent gliomas for the differentiation between tumor recurrence and scar. The enhanced ⁶⁸Ga-BZH3 seems to correlate to an overexpression of Neuromedin B.