Serum small RNAs in metastatic colorectal cancer predict response to chemotherapy and characterize high-risk patients.

Metastatic colorectal cancer (mCRC) presents significant challenges in clinical management due to its heterogeneity and variable response to treatment. In this study, we conducted comprehensive small RNA (sRNA) sequencing analyses to identify sRNA biomarkers associated with survival and treatment response in mCRC patients. We measured serum sRNAs before and after chemotherapy treatment in a discovery cohort of 189 mCRC patients. Our analysis revealed 25 microRNAs (miRNA) as significantly associated with overall survival at baseline. We found that 11 of the 25 significant miRNAs were also significant in an independent validation cohort of 20 mCRC patients, including the top five miRNAs from the discovery cohort. Importantly, all but four of the 25 significant miRNAs from the discovery cohort had hazard ratios in the same direction in the validation cohort. Among the 25 significant miRNAs, we identified the miR-320 family of miRNAs as the strongest independent prognostic marker, with high baseline levels correlating with poor survival outcomes. Furthermore, post-treatment levels of the same miRNAs were even more predictive of overall survival, emphasizing the prognostic value of serum changes in miRNA levels before and after treatment. Moreover, we observed significant changes in serum miRNAs and other sRNAs when comparing samples before and after chemotherapy, with distinct expression patterns between responders and non-responders. Leveraging these differential expression patterns, we established a serum sRNA signature that accurately predicts response to chemotherapy with an area under the curve (AUC) of 0.8. In summary, our study highlights the prognostic and predictive potential of sRNA biomarkers in mCRC, offering valuable insights into patient stratification and personalized treatment approaches.