Relationship between thallium-201 kinetics and proliferative activity assessed by monoclonal antibody MIB-1 in brain tumours

To clarify the relationship between thallium-201 chloride kinetics and proliferative activity in brain tumours, a single-photon emission tomographic (SPET) study was performed and the results correlated with monoclonal antibody MIB-1 staining of the tumour tissue. ²⁰¹Tl SPET was performed 10 min (early scan) and 2 h (delayed scan) after intravenous administration of ²⁰¹Tl (111 MBq) in 34 intra-axial tumours including 24 malignant tumours, and in 27 extra-axial tumours including one malignant tumour. Tumour ²⁰¹Tl kinetic parameters [early and delayed uptake ratios (ER and DR, respectively), retention index (RI), and the ratio of tumour delayed activity to early activity (Td/Te)] were compared with tumour tissue MIB-1 labelling indices (MIB-1 LI) representative of tumour cell proliferative activity. In the intra-axial tumours, ER and DR and MIB- 1 LI were significantly higher in the malignant tumours than in the benign tumours. ER and DR were significantly correlated with MIB-1 LI (P<0.01 and P<0.05, respectively), but RI and Td/Te were not. In the extra-axial benign tumours, ER was as high as that in the intra-axial malignant tumours, while MIB-1 LI was equal to that in the intra-axial benign tumours. There were no significant correlations between any ²⁰¹Tl kinetic parameters and MIB-1 LI. This study indicates that ²⁰¹Tl ER may be the most reliable parameter for predicting the proliferative activity of intra-axial tumours.