RESEARCH Immunohistochemical Predictors of Bone Metastases in Breast Cancer Patients

Abstract Bones are the most common metastatic site of re-lapse in breast cancer patients and the prediction of bone me-tastases (BM) risk might prompt developing preventive and therapeutic strategies. The aim of the study was to correlate imumohistochemical (IHC) expression of selected proteins in primary breast cancer with the occurrence of BM. We ana-lyzed expression of proteins potentially associated with BM in primary tumors of 184 patients with metastatic breast can-cer (113 with- and 71 without BM). Expression of estrogen receptor (ER) in primary tumor was more common in patients with- compared to those without BM (74 vs. 45 % respective-ly, p=0.0001), whereas in this subset less common was ex-pression of parathyroid hormone related protein receptor type 1 (16 vs. 34 %, respectively, p=0.007) and cytoplasmic ex-pression of osteopontin (OPNcyt; 1.9 vs. 14 %, respectively, p=0.002). The relationship between expression of ER and OPNcyt and the occurrence of BM was confirmed in the mul-tivariate analysis. The ER-positive/OPNcyt negative pheno-type was significantly more common in patients with- com-pared to those without BM (75 and 25 %, p<0.0001, respectively; HR 1.79, p=0.013). Luminal A (43 vs. 23 % respectively, p=0.009) and luminal B/HER2-positive (16 vs. 4.9 % respectively, p=0.032) subtypes were more common in patients with- compared to those without BM, whereas triple negative breast cancer subtype was less common (16 vs. 38%, p=0.002)