miR-371a-3p as a potential biomarker for monitoring disease activity and therapeutic response in metastatic seminoma and non-seminomatous germ cell tumor patients treated with BEP chemotherapy.

Abstract

616 Background: MicroRNA 371 (miR-371a-3p) is a promising biomarker for germ cell tumors. Its expression in blood may provide a non-invasive method for monitoring disease activity and treatment response. The aim of this study was to analyze miRNA-371 levels before and after BEP-chemotherapy (bleomycin, etoposide, cisplatin) in patients with metastatic seminoma and non-seminomatous germ cell tumor (NSGCT). Methods: A retrospective analysis of miR-371a-3p expression was performed in patients who received systemic BEP chemotherapy between 2022 and 2025. miRNA expression levels were quantified from serum samples using reverse transcription quantitative polymerase chain reaction (RT-qPCR). Crossing point (Cp) values were determined for each sample and converted into relative quantification (RQ) values using the ΔΔCp method. The dynamics of miRNA levels and their correlation with clinical response were evaluated. RQ levels <5 were considered negative, and >10 were considered positive. Results: MiRNA-371 levels were significantly higher before chemotherapy than after treatment (median 138.6 vs 4.19; p=0.0010) in patients with seminoma. In 7 of 11 patients, the levels dropped to undetectable, and in two patients to the indeterminate range. Two patients showed persistently positive miRNA-371 levels after chemotherapy despite radiological regression; they developed early relapse. In patients with intermediate measurements during chemotherapy (e.g. after 2 of the 3 cycles), a statistical significant (p=0.0078) decrease was also observed, although most values remained positive (median 445.5 vs 11.71). In the NSGCT cohort, data were available from before treatment and the admission day of the third treatment cycle. miR-371a-3p levels declined significantly (p = 0.0156) after two cycles of BEP. However, most patients remained positive. Pre-chemotherapy miRNA-371 levels correlated significantly with initial tumor size (Spearman r = 0,8239, p = 0.0001), while post-chemotherapy levels showed no correlation with residual tumor size (Spearman r = -0.01425, p = 0.9645). Conclusions: MiRNA-371 levels decrease significantly after PEB chemotherapy in patients with seminoma and non-seminomatous germ cell tumor. Our findings support the role of miRNA-371 as a potential biomarker for monitoring disease activity and treatment response in germ cell tumors.