292P Unlocking the potential of circulating miRNAs in predicting response to neoadjuvant chemotherapy in breast cancer: A systematic review and meta-analysis

The potential role of circulating miRNAs as biomarkers for breast cancer (BC) has been widely reported. However, the large discrepancy between studies prevents the feasibility of implementing circulating miRNAs in routine clinical practice. In BC patients undergoing neoadjuvant chemotherapy (NAC), the ability to anticipate response could lead to improve prognosis by individualizing post-NAC approach. In this scenario, the present meta-analysis aims to quantify and clarify circulating miRNAs' predictive role for NAC response in BC patients. We conducted a comprehensive literature search in 5 main medical databases until 16th February 2023, along with additional research sources. The systematic review and meta-analysis were performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and we applied the Cochrane recommended methodology for prognostic factor studies. We quantitatively pooled the effect sizes of each study by applying a random-effects model to consider within and between-study variances. Cochrane Q test (significance at 0.05) and I2 value were used to assess between-study heterogeneity. The Prediction Model Risk Of Bias Assessment Tool evaluated studies' bias risk. The meta-analysis included 15 studies, with a total of 1521 early BC patients. Overall, our findings support the hypothesis that circulating miR-21-5p and miR-155-5p may act as predictive biomarkers. Pooled area under the curve values were 0.72 (95% confidence interval (CI) 0.59-0.86, p< 0.05) and 0.67 (95% CI 0.53-0.81, p< 0.05), respectively, thus indicating an acceptable predictive ability in anticipating NAC response. To our knowledge, this is the first systematic review and meta-analysis that provides a quantitative synthesis of the predictive value of circulating miRNAs for NAC response in BC patients. However, due to the limited number of studies included in the meta-analyses and the high clinical and statistical heterogeneity, further studies are needed to confirm the predictive power of circulating miR-21-5p and miR-155-5p.