[Histological prediction of cerebral tumors using SPECT with 201T1]

SPECT with 201Tl provides information regarding the degree of malignancy of cerebral tumours, their possible relapses, the differentiation of necrotic tissue in the tumours following chemotherapy or radiotherapy and permits differentiation into zones of various grades of histological malignancy.

We carried out a prospective analysis of the usefulness of SPECT with 201Tl for the histological prognosis of cerebral tumours. For one year 68 patients diagnosed (on CT and/or MR) as having an expansive cerebral lesion were studied. The early uptake (ICP) and retention (R) indices were calculated, and these results correlated with the morbid anatomy (AP) findings and the results obtained with surgery and stereotactic biopsy. Four patients were excluded due to lack of AP results.

Significant differences were found between the ICP of grade I-II astrocytomas (1.34 +/- 0.52) and glioblastomas multiformes (2.56 +/- 0.57), between the ICP of meningiomas (4.53 +/- 1.68) and metastases (2.45 +/- 0.58) and between those of meningiomas and all glial tumours. With regard to IR, we saw significant differences between the figures for meningiomas (0.63 +/- 0.13) and meningiomas with malignant relapses (0.94 +/- 0.17) and between metastases (0.8 +/- 0.03) and all glial tumours.

From our study, it may be concluded that rapid, high captation of 201Tl (high ICP) with a slow fall (high IR), is associated with a process showing malignancy on histological study (malignant relapse of meningioma, glioblastoma multiforme, metastasis), whilst high take-up (high ICP) with rapid elimination (low IR) corresponds to a benign hypervascularized tumour (meningioma).