PTEN protein expression in postmenopausal steroid receptor positive early breast cancer patients treated with adjuvant tamoxifen

Abstract

Purpose: Since one of possible causes of resistance to antiestrogen therapy in steroid receptor positive (SR+) breast cancer (BC) patients is an alteration of PTEN (phosphatase and tensin homolog deleted on chromosome 10) signaling pathways, the aim of this study was to determine the PTEN protein expression in postmenopausal patients with steroid SR+ BC treated with adjuvant tamoxifen, to investigate the association of PTEN protein expression with tumor histology, size and grade, estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) statuses and disease outcome. Methods: This was a retrospective analysis of 78 postmenopausal stage I/II SR+ BC patients treated with adjuvant tamoxifen. PTEN protein expression and ER, PR and HER2 status were determined using immunohistochemistry. Results: The distribution of PTEN protein expression according to tumor histology was as follows: PTEN+ status in 27/43 (62.8%) patients with ductal and in 26/35 (74.3%) patients with lobular carcinomas; and PTEN- status in 16/43 (37.2%) patients with ductal and in 9/35 (25.7%) patients with lobular carcinomas. Disease relapse was observed in 38/78 patients: 14/53 (26.4%) of PTEN+ BC subgroup and 24/25 (96%) of PTEN- subgroup (x2,=0.018). There were no significant associations between PTEN protein expression and tumor histology, size and grade, and ER, PR and HER2 expression. Patients with PTEN- had significantly shorter disease-free interval (DFI) and overall survival (OS) (for both, log rank test, p <0.01) compared to PTEN+ BC patients. Conclusion: Our results suggest that PTEN protein expression might be of prognostic significance in postmenopausal SR+ BC patients treated with adjuvant tamoxifen. © 2011 Zerbinis Medical Publications.