Evaluation of tumor viability in Post radiation therapy pediatric brain tumors with 99mTc- glucoheptonate single photon emission computed tomography (SPECT)

Brain single photon emission computed tomography (SPECT) with 99mTc- glucoheptonate, a blood brain barrier imaging agent, is rapidly regaining interest after it has been shown that the uptake of tumor seeking agents like thallium, tetrofosmin, sestamibi and pertechnate by brain tumors is solely dependent on disruption of the blood brain barrier. Therefore, the use of 99mTc glucoheptonate may yield the same diagnostic information as other agents such as the much more expensive 99mTc-sestamibi. The purpose of the study was to evaluate 99mTc-glucoheptonate as an imaging agent for recurrent primary brain tumors in children. Methods: Fifty-one patients aged 5-18 years were evaluated for tumor recurrence following radiotherapy for primary malignant brain tumors, using brain single photon emission computed tomographies (SPECT) with 99mTc-Glucoheptonate. Contrast enhanced computerized tomography (CT) of brain was performed in all patients within + 1 week of brain SPECT as a diagnostic standard and compared. Results: Recurrent tumors showed avid 99mTc- glucoheptonate concentration and a high 99mTc-glucoheptonate retention index (6.06 + 1.41) compared with post radiation gliosis, which showed no 99mTc-glucoheptonate concentration over the affected site and had a 99mTc-glucoheptonate retention index of 1.10 + 0.18 (p=0.001). 99mTc- glucoheptonate SPECT had a sensitivity of 79.48% and a specificity of 91.66% when compared with contrast-enhanced computed tomography as a gold standard. However, this technique did not show good performance in the differential diagnosis of lesions in posterior fossa. Conclusion: This study suggests that 99mTc-glucoheptonate brain SPECT can be used as a sensitive and specific diagnostic test to differentiate recurrent tumor from post radiation gliosis, with the exception of tumors located in posterior fossa. Further studies should address this limitation before definite protocols are established.