In a SWOG prospective cohort, microRNA 371a-3p (miR371) predicted relapse risk in early-stage testicular cancer, but experts flagged uncertainty about clinical utility. Interim results from the S1823/GCC.1 study presented at ASCO showed miR371’s specificity and negative predictive value for relapse detection, with relapse-risk stratification based on serial plasma sampling after orchiectomy. The study enrolled patients within 56 days of surgery and measured miR371 via real-time PCR, grouping participants into low-, moderate-, and high-risk relapse cohorts. In the low-risk group, estimated relapse risk was about 10%, while the moderate-risk group included about 50% relapse risk participants, such as LVI-positive nonseminoma at clinical stage IIa. Lead investigator Lucia Nappi said retrospective work has suggested miR371 as a biomarker of active disease, but prospective confirmation—especially in early disease—remains the critical step. The key question now is whether the biomarker can change management beyond surveillance, such as escalation or de-escalation of follow-up and treatment interventions.