Breast cancer (BC) is a heterogeneous disease with distinct morphological features and clinical behavior. It is the most common type of cancer in women Worldwide and in Oman where it presents at advanced stages in young females and has an aggressive biological behavior. Locally Advanced Breast Cancer (LABC) care has been revolutionized by the introduction of the preoperative chemotherapy -Neo-adjuvant chemotherapy (NAC) and is now considered as the standard of care for patients with LABC that allows breast conservation and improved survival in a subset of patients who achieve complete pathological response. The ultimate question has been whether the patients who will have a better outcome in terms of response and survival can be predicted? Two groups of molecules have been advocated to serve such purpose; namely miRNAs and cancer related proteins (CRPs). MiRNAs are small non-coding RNAs that have been shown to play a vital role in cancer progression. The CRPs are diverse group of proteins that serve essential cellular processes that are altered during carcinogenesis and its treatment in a way that it may predict the clinical outcome. Therefore, the aim of the study was to evaluate miRNA and CRPs alterations during NAC by multiple sampling of tissue and serum and correlate it with clinico-pathological features, clinical and pathological responses, and survival to identify potential predictive and prognostic molecular markers. Methods: Tissue and serum samples were collected at four time points from LABC patients undergoing NAC, including time of diagnosis, after 1st and 4th cycle of Adriamycin/cyclophosphamide treatment, and after 4th cycle of Docetaxel administration. The relative expression of tissue miRNAs was expressed using Significance Analysis of Microarrays (SAM) analysis and heat map was generated by Hierarchical Clustering. A panel of 4 miRNAs (miR-451, miR-3200, miR-21 and miR-205) in serum samples was further validated using Qrt-PCR. Ninety-two CRPs were studied using Proximity Extension Assay (PEA). The alterations of serum levels of miRNA and CRPs, associations with clinical and pathological responses, correlation with clinico-pathological features, and survival outcome were studied using Friedman, Mann-Whitney U, Spearman and Wilcoxon signed ranks and Wilcoxon signed ranks tests. P values of 0.05 or less was considered statistically significant. Calculations were performed using Statistical Package for the Social Sciences (SPSS) v.21.0 Software. Results: A total of 32 tissue samples and 108 serum samples from eight patients and 27 patients were analyzed respectively in miRNA study. MicroRNA expression profiling of tumor verşus normal tissue revealed more than 150 differentially expressed miRNAs. Serum miR-451 showed significant decrease in its level during treatment and higher serum levels were associated with improved clinical and pathological responses and disease free survival. The serum levels of miR-3200 declined during NAC and higher serum levels at baseline were associated with lower residual breast cancer burden and relapse rates. A total of 132 serum samples from 33 patients were analyzed respectively in the CRP study. Thirty five proteins exhibited significant changes during the treatment. Pre-operative serum VEGF correlated with pathologically responding patients whereas, IL-2Ra correlated with clinical response. Amphiregullin (AR) at time of diagnosis showed a significant elevation in the pathologically non-responding patients compared to the responders which also has been observed in PRL, ErBb2 and OPG. Low expression levels of serum VEGF and PRL at baseline was associated with better patients' Disease Free Survival (DFS). Moreover, low serum VEGF at baseline was also associated with better patients OS. Interactome analysis showed the interaction between EGFR, EGF and Fas proteins which their correlation was supported in our findings. Conclusion: There are variations in serum miRNA and CRP levels during NAC treatment, which may be of prognostic significance in terms of response and survival outcomes in patients receiving NAC for LABC.