SP8.02 Somatostatin Receptor (SSTR) expression and the clinical prognostic relevance in clinical breast cancer

Introduction Somatostatin Receptors (SSTRs), regulate secretion of hormones, being located on membrane /cytoplasmic regions of cells, anchoring PDZ domain proteins including MUPP1/MPDZ (essential cellular tight junction assembly). Their clinical relevance in breast is unclear. Method qPCR was used to analyse expression levels of the five somatostatin receptors in an existing cohort of breast cancer tissues. Results Breast tumour tissues expressed higher levels of SSTR1 (p=0.0012) and SSTR4 (p=0.011). Expression of SSTRs1-3 correlated with poor OS (p<0.001/p=0.011/p=0.010). SSTRs1-3 were also associated with DFS (p<0.001/p=0.002/p=0.043). Integrated expression levels presented a clear prognostic factor for overall survival (p=0.008/HR=1.873) independently of other clinical parameters (OS predication: p=0.005/HR=2.877); NPI showed independent predictive value (p=0.018). DFS was a significant prognostic factor (p=0.001/HR=2.231). Integrated expression was an independent factor for DFS (p=0.009/HR=2.599), ER status (p=0.045), Her2 (p=0.027), clinical prognostic index (p=0.018) using multivariate analysis (Cox model). Further stratification using ER/HER2 indicated that integrated SSTR expression predicted OS and DFS in different hormone status. Integrated SSTR expression had a much stronger prediction power for OS for patients with non-triple negative breast cancer (TNBC p=0.002) than TNBC (p=0.018 TNBC) with HR at 2.573 (95% (CI) 1.312-5.047). The same pattern applied to DFS (p=0.001/p=0.172), HR at 2.160 (95% CI 1.331-3.507) Discussion Our study has shown that expression of Somatostatin receptors, SSTR1, SSTR2 and SSTR3 are significantly correlated with the disease progression and clinical outcome in patients with breast cancer. The pattern of expression is thus a prognostic indicator and aberration of the receptors may constitute opportunities for therapeutic consideration.