Implementation of serum microRNA-371a-3p testing for testicular germ-cell tumors in a pathology department: Real-world data from a comprehensive cancer center.

5025 Background: The classical serum tumor markers for testicular germ cell tumor (TGCT) patients show limited sensitivity and specificity in some clinical settings. In the last years, serum miR-371a-3p testing has been shown to have superior performance for the detection and follow-up of TGCT patients. A commercial test with IVD approval is already available for use in the clinic. In this work we demonstrate our experience with the clinical implementation of this liquid biopsy test, comparing its performance with the one of AFP, HCG and LDH. Methods: The M371 test (serum) was implemented at the Department of Pathology of our Comprehensive Cancer Center in August 2024, for patients presenting with testicular masses and for TGCT patients during follow-up. Simultaneous collection of AFP, HCG and LDH was performed at the different timepoints, following the guidelines for diagnosis and follow-up of TGCT patients. Blood was collected on the recommended Serum-Gel 7.5mL tubes and processed to serum within 3h of collection. The RTqPCR test and analysis followed the manufacturer's closed protocol (IVDR approved). Clinical charts and CT scans were reviewed to determine disease status, and results were correlated with histology. Results: A total of 128 M371 tests were performed at the Department of Pathology during 16 months, including several contexts of the disease (pre-orchiectomy, follow-up, pre-RPLND, pre and post-chemotherapy). The mean turnaround time for the test (from receiving the blood sample to issuing the report) was of 5.6 days. The median patient age was 35 years (19-81 years). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were as follows: 0.43, 0.96, 0.76 and 0.85 for AFP; 0.57, 0.98, 0.89 and 0.88 for HCG; 0.37, 0.91, 0.55 and 0.82 for LDH; 0.80, 0.92, 0.77 and 0.93 for the combination of AFP+HCG+LDH; and 0.96, 0.96, 0.87 and 0.99 for M371 test alone. Additional collections/testing and subanalyses based on disease setting and histologic findings are ongoing. Conclusions: The M371 IVD serum test alone showed a superior diagnostic performance for detecting active TGCT in an unselected, consecutive cohort of TGCT patients representing different settings of the disease, when compared to the classical serum tumor markers AFP, HCG and LDH, isolated or in combination. The sensitivity of AFP, HCG and particularly LDH isolated (0.43, 0.57 and 0.37) were outperformed by the sensitivity of the M371 test (0.96). The high NPV of the M371 test (0.99) may aid in the decision of de-escalating intervention (treatment or follow-up measures) of young TGCT patients. These real-world data underscore the potential advantages of adding microRNA testing as a an additional test to combine with classical serum tumor markers and imaging.