Expression of mediated P-glycoprotein multidrug resistance related to Tc-99m MIBI scintimammography results

We prospectively studied a total of 24 patients with breast cancer to evaluate the relationship between the degree of accumulation of technetium-99m sestamibi (Tc-99m MIBI) and p-glycoprotein (Pgp) expression in tumor tissues. All 24 patients underwent Tc-99m MIBI scintimammography before surgery or biopsy. Immunohistochemical studies were performed on multiple non-consecutive sections of the same tumor using a Pgp specific monoclonal antibody. JSB-1. Planar images were started 10 min after injection of Tc-99m MIBI. Tumor to background (T/B) ratios calculated from the planar images were correlated with Pgp expression as determined by immunohistochemical studies. The TIE ratios were significantly lower for tumors in eight patients with positive Pgp expression (Group 1) than in 16 patients with negative expression (Group 2) (1.40 +/- 0.11 and 2.76 +/- 0.60, P < 0.05). Our data confirmed that Tc-99m MIBI scintimammography is useful for determination of the presence of multidrug resistance due to Pgp expression in patients with breast cancer. (C) 2000 Elsevier Science Ireland Ltd, All rights reserved.