[Relationship between P-glycoprotein function in peripheral blood cells and multidrug resistance in breast carcinoma].

To analyze the relationship between P-glycoprotein function in peripheral blood cells and primary multidrug resistance in breast carcinoma. P-gp function was investigated by flow cytometry in NK cells of 16 breast cancer patients treated with anthracyclines and taxanes. Among all the patients, 8 were in chemotherapy-sensitive group and 8 in chemotherapy-resistant group. P-gp function was determined by rhodamine 123 (Rh123)-ejection test. Mathematical model was established by a regression of the fluorescence-time curve. The efflux rate constants of the chemotherapy-sensitive and -resistant groups were compared. There was no significant difference of Rh123 accumulation, retention or efflux between the two groups. The mathematical model of F(t) = F(0) · e(-kt) was established. K was the efflux rate constant, which was significantly different between the chemotherapy-sensitive and -resistant groups (P = 0.025). When k > 3.9 was used as diagnostic criterium for primary resistance, the sensitivity, specificity and accuracy were 75.0%, 100% and 87.5%, respectively. P-glycoprotein function in peripheral blood cells is associated with primary multidrug resistance in breast carcinoma. The efflux rate constant may be a good predictor for chemotherapy sensitivity.