Technetium-99m sestamibi brain SPECT in the follow-up of glioma for evaluation of response to chemotherapy: first results.

Abstract

The initial treatment of high-grade glioma often consists of surgery and radiation therapy. Chemotherapy is used in cases of recurrence or after incomplete surgery. Because of the many potential serious side-effects of chemotherapy, early tumour response evaluation is necessary to enable clinicians to adapt the treatment. However, response monitoring with computed tomography (CT) or magnetic resonance imaging (MRI) is often difficult. The aim of this study was to assess the value of repeated technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) single-photon emission computerised tomography (SPECT) for this purpose. Fifteen patients with malignant glioma were investigated with MIBI SPECT. Imaging was performed 1 h after the intravenous injection of 555 MBq of (99m)Tc-MIBI, using a dedicated SPECT system (Tomomatic 564, Medimatic, Denmark). Overall, 57 investigations were performed. A MIBI uptake index was computed as the ratio of counts in the lesion to those in the contralateral region. Previous study had shown a cut-off value of 2.0 to be appropriate. SPECT indices were compared with neurological evaluation, CT or MRI. This assessment was performed every 4 months during and after the treatment. Six patients showed an increased MIBI index associated with clinical or radiological progression of disease during chemotherapy. After an initial response to therapy, three patients showed an increased MIBI index despite chemotherapy, demonstrating secondary resistance to therapy. Six patients showed a decreased MIBI index, demonstrating a good response to therapy. The first nine patients died shortly after the last SPECT scan (average duration of survival, 4 months). The therapeutic protocol was modified in six cases, but successfully so in only two. In some cases, tumour progression was diagnosed earlier with SPECT than on the basis of clinical or MRI signs. Early response or resistance to chemotherapy is detectable by(99m)Tc-MIBI SPECT. Therefore this functional imaging modality could be considered as a valuable tool to permit effective adaptation of the therapeutic regimen in patients treated for recurrent high-grade glioma.