Plasma Small RNAs as Predictive and Monitoring Biomarkers for Combination Immunotherapy in Advanced Gastric Cancer.

BACKGROUND: Immunotherapy has become a new standard treatment for advanced gastric cancer (aGC). However, current biomarkers are insufficient for accurately identifying true responders, emphasizing the need for novel biomarkers. METHODS: Between December, 2020, and October, 2023, we recruited 91 consecutive aGC patients (49 in the discovery and 42 in the validation cohorts). Plasma samples were collected at baseline and after two cycles of immunotherapy. We conducted small RNA (sRNA) next-generation sequencing on 140 samples. Additionally, we investigated previously reported potential biomarkers, including PD-L1 combined positive score (CPS), inflammation scores, and serological tumor biomarkers. RESULTS: In the discovery cohort, we identified two pre-treatment sRNAs significantly associated with response to immunotherapy: high levels of hsa-miR-3916 (p = 0.020) and low levels of hsa-miR-181d-5p (p = 0.046), confirmed in the validation cohort (p = 0.011 and p = 0.013, respectively). The AUCs for predicting response using these two sRNAs were 0.77 (95% CI; 0.62-0.93) and 0.83 (95% CI; 0.71-0.96), respectively. When integrating PD-L1 CPS with these two sRNAs, the AUCs were 0.82 (95% CI; 0.68-0.96) and 0.83 (95% CI; 0.70-0.97) for the discovery and validation cohorts, respectively. Furthermore, when combining PD-L1 CPS and serological tumor biomarkers with these two sRNAs, the AUCs were 0.89 (95% CI; 0.79-1.00) and 0.83 (95% CI; 0.70-0.96) for the discovery and validation cohorts, respectively. After combination immunotherapy, responders exhibited decreased levels of hsa-miR-320c (p = 0.006) and increased levels of hsa-miR-26b-5p (p = 0.007). Additionally, patients with decreased hsa-miR-320c demonstrated a trend towards improved PFS (median: 9.17 vs. 3.03 months, p < 0.001) and OS (median: 16.43 vs. 10.23 months, p = 0.115). CONCLUSION: These findings provide valuable insights into the sRNA features associated with response to combination immunotherapy in aGC patients and suggest potential biomarkers useful for selecting patients likely to benefit from immunotherapy.