The study of relationship between breast cancer 99Tcm-MIBI imaging with the expression of P-glycoprotein and multidrug resistance-associated protein

Objective: To evaluate the relationship between the uptake, washout of 99Tcm-methoxy-isobutylisonitrile (MIBI) and P-glycoprotein (P-gp) or multidrug resistance-related protein (MRP) expression in 36 breast cancer patients. Methods: 36 patients with untreated breast cancer were studied prospectively a week before surgical operation, all were injected intravenously with 740 MBq 99Tcm-MIBI in the arm contralateral to the lesion. Anterior planar images were acquired at 10 and 180 min after injection and the tumor-to-normal breast ratios (T/N) and washout rates (WR) were calculated. Immunohistochemical analyses of P-gp and MRP expression were used to evaluate the removed tumor tissues after operation and categorized into four groups. The differences of the early T/N ratios, the late T/N ratios and the WR among them were compared. Results: The early T/N ratios in group A and B were higher than that in group D. There was statistic difference between group A and D (P=0.001 ), and also in group B and D (P=0.045). The late T/N ratios had no statistic differences among them (F=0.499, P=0.686). The WR of group A, B, C were higher than that in group D and there were significant differences between them (P<0.001, P<0.001, P<0.001 and P=0.014 ). Conclusions: A strong positive correlation was found between the WR of 99Tcm-MIBI from the lesions and expression of P-gp or MRP in untreated breast cancer patients. 99Tcm-MIBI imaging with washout analysis might be a useful method for evaluating P-gp or MRP overexpression and their function in breast cancer. (authors)