100 patients with breast cancer (stage II, III, IV), treated at CI "Zaporizhzhia regional clinical oncology dispensary" RC. Expression BCRP was observed in 60,0% of patients, MRP1 - in 43,0%, Pgp - in22,0%. Mutual expression of both ABC-transporters was observed in 29,0% of patients, mutual expression of three ABC - transpoters - in 11,0%, in general mutual expression of two or three transporters was observed in 40,0% of patients. Most oftenencountered coexpression MRP1 and BCRP 87,5% of all cases of mutual expression of 35 patients out of 40. The patients with ABC-expression were 34,0%, ABC-negative were 26,0%. In general phenotype of MDR was observed in 74,0%. The patients were divided into two groups based on an analysis of the expression of the three ABC-transporters : 1) "without membrane expression" - 73 people (73,0%), patients whose tumors did not have membrane expression of ABC-transporters with the presence of any level of cytoplasmic expression 1+ / 2+/ 3+, or without expression of ABC-transporters at all; 2) "Membrane expression" - 27 people (27,0%), patients whose tumors had membrane expression of the one or two ABC-transporters. Both groups were examined and received chemo-therapeutic treatment according to standards. Patients who were from group of the "membrane" expression of ABC-transporters had a progression on the background of HT in 74% of cases, whereas in the whole group of patients under study, progression was observed in25% of cases P<0,001. Mutual membrane expression of both ABC-transporters was associated with progression to the background of treatment in 87,5% of cases , while progression as a whole in the group of the membrane expression was 74%. It is concluded that the membrane nature of expression and mutual expression has a negative predictive significance, and it is associated with progression to the background of treatment. Cytoplasmic expression, mutual expression of the two or three transporters was not associated with progression on the background of CT (progression was only in 4,2 - 6,6% of cases). These variants of expression have a positive predicative significance. Found that the group of the "membrane expression" was significantly different (had a worse three-year PFS) from the group "All patients" (р = 0,0005) and from the group "without membrane expression" (р = 0,0001). Moreover the subgroup "without membrane expression" and "All patients" did not have the statistically significant difference for three years non-recurring survival (р=0,232). The fact of membrane expression ABC-transporters had negative predictive significance.
