Association Of Tumor Washout Rates Nd Accumulation Of Technetium-99m-MIBI With Expression Of P-glycoprotein In Lung Cancer

~umosa~ In a prospective study, we correlated the washout rates of 99uTc-sestanibi (MIBI) and the degree of MIBI accumulation with the expression of P-glycoprotein (Pgp) in tumor tissues in a total of 46 patients with lung cancer. MEI1IOI)S: All patients underwent early (30 mm) and delayed (3 hr) MIBI imaging before initiation of cbemo- or radiotherapy. All patients had radiologically detectable tumors. Iunohistocheuical studies were performed on paraffin sections using a monoclonal antibody, P-170, developed against the internal epitope of Pgp. Normal tissue and tumor washout rates and tumor-to-background ratios were correlated with the level of Pgp expression. RESULTS: There was an inverse correlation between tumor-to-background ratios and the density of Pgp (p< 0. 001), whereas there was no appreciable correlation between tumor washout rates of MIBI and the level of Pgp expression (p>0. 1). C(I4CWSI(14: The current data strongly suggest that, although the reduced ability for the tumors to accumulate MIBI correlates well with the increased levels of Pgp expression, tumor washout rates of M]IBI do not correlate with the density of Pgp in tumor tissues. cytometry.