CLINICAL VALIDATION OF THE INFLUENCE OF P-GLYCOPROTEIN ON TECHNETIUM-99M-SESTAMIBI UPTAKE IN MALIGNANT-TUMORS

We prospectively studied 48 patients with either breast cancer (30 pat ients) or lung cancer (18 patients) to ascertain the relationship betw een the degree of accumulation of Tc-99m-sestamibi and the expression of p-glycoprotein in tumor tissues. Methods: During initial presentati on (37 patients) or post-therapy evaluation (11 patients), the patient s underwent contemporaneous Tc-99m-sestamibi imaging and biopsy (30 pa tients) or surgery (18 patients). The interval between surgery/biopsy and imaging Varied between 3 and 15 days. All patients had radiologica lly detectable tumors. Immunohistochemical studies were performed on p araffin sections using a monoclonal antibody, JSB-1, developed against the internal epitope of p-glycoprotein. Tumor-to-background ratios we re correlated with the level of p-glycoprotein expression determined b y immunohistochemical studies. Results: Our results showed an inverse correlation between the tumor-to-background ratios of Tc-99m-sestamibi and the density of p-glycoprotein expression in tumor tissues. The va lues for the tumor-lo-background ratios were significantly lower for t hose tumors expressing p-glycoprotein at high levels than those with s cattered and no expression (p < 0.01 and p < 0.001, respectively). Con clusion: Although our results warrant further studies at the molecular revel using PCR techniques after the extraction of mRNA, our data str ongly suggest that Tc-99m-sestamibi imaging is useful to noninvasively determine the presence of multidrug resistance in patients with malig nant tumors.