ASSOCIATION OF TUMOR WASHOUT RATES AND ACCUMULATION OF TECHNETIUM-99M-MIBI WITH EXPRESSION OF P-GLYCOPROTEIN IN LUNG-CANCER

In a prospective study, we correlated the washout rate of Tc-99m-sesta mibi (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. Methods: All patients underwent early (30 min) and delaye d (3 hr) MIBI imaging and bronchoscopic biopsy before initiation of ch emo- or radiotherapy. The interval between biopsy and imaging varied b etween 2 and 10 days. All patients had radiologically detectable tumor s. Immunohistochemical studies were performed on paraffin sections usi ng a monoclonal antibody, JSB-1, developed against the internal epitop e of Pgp. Normal tissue and tumor washout rates and tumor-to-backgroun d ratios were correlated with the level of Pgp expression. Results: Th ere was an inverse correlation between tumor-to-background ratios and the density of Pgp (p = 0.001), whereas there was no appreciable corre lation between tumor washout rates of MIBI and the level of Pgp expres sion (p = 0.414). Conclusion: The current data strongly suggest that, although the reduced ability for the tumors to accumulate MIBI correla tes well with the increased levels of Pgp expression, tumor washout ra tes of MIBI do not correlate with the density of Pgp in tumor tissues. Our results also warrant additional research for correlating immunohi stological and imaging findings with messenger RNA levels determined b y polymerase chain reaction and flow cytometry.