Correlation between uptake of 99TcM-MIBI and multidrug resistant proteins of breast cancer

Objectives: To assess the correlation between 99Tcm-MIBI uptake and the expression level of multidrug resistant proteins of breast cancer. Methods: Thirty patients with infiltrating ductal carcinoma were enrolled in this study. 99Tcm-MIBI scintigraphy were performed at 15 min and 90 min after injecting the tracer. The uptake of 99Tcm-MIBI were evaluated as tumor over background ratio with region of interest technique. Such indexes as early uptake ratio (EUR), delay uptake ratio (DUR) and retention index (RI) were calculated respectively. P-gp (P-glycoprotein) and MRP (multidrug resistant-associated protein) expression in surgically resected tumors were investigated by immunohistochemistry. Immunohistochemistry HPIAS-1000 image analysis system was used to determined the level of P-gp and MRP expression. The difference of P-gp and MRP level in the group with RI ≥ 0 and the group with RI<0 was compared using independent student t test. The correlation between RI ,P-gp and MRP were analyzed by Pearson correlation and partial correlation analysis. Results: The expression of P-gp and MRP in tumor tissue were 0.1183±0.0700 and 0.1195± 0.0522, respectively. In group with RI < 0, the P-gp and MRP were 0.2181±0.0384 and 0.1718±0.0479. In group with RI ≥0,the P-gp and MRP were 0.1057±0.0217 and 0.0967 ±0.0362. There were significant differences in P-gp, MRP between the two groups ( t = 6.61 and P =0.0001 for P-gp,t = 5.01 and P =0.002 for MRP, respectively). There was positive correlation between P-gp and RI (r =-0.919,P =0.001 ),DUR (r =-0.675,P =0.001),MRP (r =0.549,P =0.001), respectively. There was no correlation between P-gp and EUR (r =-0.097,P =0.610).There was positive correlation between MRP and RI (r =-0.547,P =0.002), but no correlation between MRP and EUR (r =0.292,P =0.117) or DUR (r=-0.173,P =0.361). Partial correlation statistic analysis showed that there was high positive correlation between P-gp and RI (r =-0.8847,P =0.001), but no significant correlation between MRP and RI (r =-0.1296,P =0.512) Conclusions: It is suggested that increased level of P-gp expression may contribute to a low accumulation of 99Tcm-MIBI on delayed scans in breast cancer. The uptake of 99Tcm-MIBI may be not related to the levels of MRP expression. Thus 99Tcm-MIBI scintigraphy may predict the MDR development which associated with P-gp expression in breast carcinoma. (authors)