[Correlation between uptake of 99Tcm-MIBI and expression of multidrug resistant protein in breast cancer].

OBJECTIVE: To assess the correlation between uptake of (99)Tc(m)-MIBI and expression level of multidrug resistant protein in breast cancer.

METHODS: Thirty pathologically confirmed patients with primary invasive ductal carcinoma were examined by (99)Tc(m)-MIBI scintigraphy at 15 min and 90 min after injecting the tracer. The uptake of (99)Tc(m)-MIBI at the region of interest (ROI) was evaluated as tumor to normal background (T/N) ratio. Retention index (RI) was calculated from the early uptake ratio (EUR) and updelayed take ratio (DUR). The expression of P-glycoprotein (P-gp) and multidrug resistant-associated protein (MRP) was detected by immunohistochemistry and the results were expressed as optical density (A). The data were analyzed by t test, Pearson correlation and partial correlation analysis.

RESULTS: The expression of P-gp and MRP in tumor tissue was 0.1183 +/- 0.0700 and 0.1195 +/- 0.0522, respectively. In group with RI < 0. the expression of P-gp and MRP was 0.2181 +/- 0.0384 and 0.1718 +/- 0.0479, respectively. In group with RI >/= 0, the expression of P-gp and MRP was 0.1057 +/- 0.0217 and 0.0967 +/- 0.0362, respectively. There were significant differences between the two groups (t = 6.61, P = 0.0001; t = 5.01, P = 0.002). 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, but 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 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).

CONCLUSION: The study suggests that increased level of P-gp expression may contribute to a low accumulation of (99)Tc(m)-MIBI in breast cancer, but no correlation with the expression level of MRP. Thus (99)Tc(m)-MIBI scintigraphy may predict the MDR development associated with P-gp expression in breast carcinoma.