Influence of Glioma's Multidrug Resistance Phenotype on 99mTc-Tetrofosmin Uptake

Multidrug resistance (MDR) remains a major obstacle to successful chemotherapeutic treatment of cancer. Several chemotherapeutic and radiopharmaceutical agents are substrates of the pumps encoded by the MDR genes, and therefore, their accumulation is prevented. We evaluated in vivo whether [Tc-99m]tetrofosmin (Tc-99m-TF) uptake is influenced by the MDR profile of gliomas. Eighteen patients with histologically confirmed glioma were included in the study. Brain single-photon emission computed tomography by Tc-99m-TF was performed within a week prior to surgical excision, and the expression of MRP5 was assessed by immunohistochemistry. Radiotracer accumulation was assessed by a semiquantitative method, calculating the lesion-to-normal uptake ratio. Using Spearman's rho analysis, we found no correlation between tracer uptake expressed as lesion-to-normal and MRP5 expression. There was a significant correlation between glioma aggressiveness as assessed by Ki-67/MIB-1 and MRP5 expression. The present data suggest that Tc-99m-TF uptake is not influenced by glioma's MDR phenotype. Thus, Tc-99m-TF constitutes a suitable radiotracer for imaging gliomas.