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Inhibitor of apoptosis (IAP) family proteins is involved in mechanisms of resistance to apoptosis in various cancer cells. The aim of this study was to assess the expression of selected IAP proteins such as XIAP, cIAP-1, cIAP-2 and survivin in breast cancer patients and evaluates their relationship with the prognostic and predictive factors and their impact to overall survival (OS) and progression free survival (PFS). The study was conducted with the use of tissue samples prospectively collected from 92 previously untreated female breast cancer patients. The control encompassed 10 fibroadenoma patients. The expression of XIAP, cIAP-1, cIAP-2 and survivin was assessed using flow multicolor cytometry. XIAP expression was present in 99 % of the breast cancer patients (91/92) with the median expression 13.65% (range 1-66.8%). Expression of XIAP in breast cancer was significantly higher compared to the control group (p=0.006). Median expression of cIAP-1, cIAP-2 and survivin in the study group was 25.95% (range 0.8-83.7%), 16.7% (range 1-53.2%) and 4.6% (range 0-43%) respectively. In the rank Spearman test, strong correlations (p<0.001) were seen among the expressions of XIAP, cIAP-2 and survivin, in all combination. Additionally, week correlation between XIAP and cIAP-1 was observed (p=0.02). The median expression of XIAP and survivin was significantly higher in more advanced tumors (stages pT2/pT3 vs. pT1). The median PFS and OS in breast cancer group were 46.15 and 47.1 months respectively. No significant correlations were observed among expressions of IAP family proteins and survival. However, low expression of XIAP in breast cancer showed trend to longer PFS (p=0.08). XIAP, cIAP-1 cIAP-2 and survivin participate in antiapoptotic mechanisms in breast cancer and XIAP and survivin seem to have the most significant prognostic importance. Further studies are needed to establish more complete prognostic and predictive values of IAP family proteins in breast cancer patients.