Rationale: Malignant astrocytomas show thallium uptake with a high target-to-background ratio, allowing the use of radioguided surgery.
Method: We report on 6 patients (3 men) diagnosed with malignant astrocytoma. All patients signed informed consent documents. Previous thallium-201 SPECT was performed, showing uptake in tumors. In the operating room we injected 37 MBq (1 mCi) of thallium-201 at the same time the craniotomy was performed. With the gamma probe we confirmed the tumor uptake, and a biopsy sample was taken. After conventional tumor resection, we scanned the surgical bed with the gamma probe. All areas of abnormal uptake were evaluated by the surgeon and, if possible, removed.
Results: In all patients the biopsy confirmed a high-grade astrocytoma. In all cases we found residual uptake in the surgical bed that was confirmed as residual tumor by pathologic examination. In 3 cases it was not possible to remove all the sites of pathologic uptake because critical areas were involved. In the other 3 patients, only background activity was found after the procedure.
Conclusion: Radioguided surgery in brain tumors with thallium-201 is a complex technique and expertise in radioguided surgery and neuroimaging is needed, but we think that it is promising.