What is the value of emission tomography studies in patients with a primary glioblastoma multiforme treated by Ir-192 brachytherapy?

Background. We studied the use of (201)Thallium SPECT and L-[1-C-11]-tyrosine PET in patients with a primary glioblastoma multiforme treated with Ir-192 brachytherapy after surgery and external beam radiation therapy. We hypothesised that the patients most likely to benefit from further surgery after deterioration would be those with radiation necrosis and would be recognised by a negative emission tomography scan.

Methods. Twenty-one patients underwent (201)Thallium SPECT performed before brachytherapy, and this was repeated in 19 patients when recurrence was suspected. Nine patients also underwent a PET scan at the same time. Nine patients underwent a second operation.

Findings. SPECT and PET were highly concordant concerning the prediction of radionecrosis and/or tumour recurrence. Repeat surgery did not lead to a significant increase in survival. There was no significant association between the duration of survival and tumour-to-background ratio but the number studied was small. Both SPECT and PET showed highly active lesions, which were proved to be recurrent tumour by clinical and histological follow-up.

Conclusion. Although PET and SPECT are both highly sensitive in detecting active tumour tissue, emission tomography was not clinically valuable in the investigation of patients with a primary glioblastoma treated with brachytherapy.