99mTc-MIBI brain SPECT as an indicator of the chemotherapy response of recurrent, primary brain tumors

Background Malignant brain tumors carry a pejorative prognosis and necessitate aggressive therapy. Chemotherapy can be used in cases of tumor recurrence. With limited response rate and potential toxicity to chemotherapeutic treatment in patients with recurrent glioma, reliable response assessment is essential. Aim To define the place of Tc-99m hexakis 2-methoxyisobutylisonitrile (Tc-99m-MIBI) Single Positron Emission Computed Tomography (SPECT) in monitoring chemotherapy response in recurrent primary brain tumors. Methods In a retrospective analysis, thirty patients were investigated with MIBI SPECT. Imaging was performed 1 h after the intravenous injection of 555 MBq of Tc-99m-MIBI using a dedicated SPECT system. A MIBI uptake index (UI) was computed as the ratio of counts in the lesion to those in contralateral region. For all patients, we compared changes over time in UI with MRI and clinical data. Results The changes in UI agreed well with the clinical and MRI-based assessments in 97% of cases. In 44% of these cases, the scintigraphic response appeared before the MRI response. In instances of treatment failure or rebound, the concordance between scintigraphy and MRI was 52%, and the scintigraphic response appeared before the MRI response in 48% of cases. Conclusion This study confirms our previous results obtained on a short series of patients with recurrent glioma, concerning the usefulness of MIBI SPECT in prediction of chemotherapy response. Moreover, in cases of tumor progression, we show that MIBI SPECT is an earlier indicator of escape from chemotherapy, an average 4 months before MRI changes.