Validation of plasma miR-371a-3p expression in patients with metastatic and early stage germ cell tumor.

Abstract

526 Background: Identification of relapsing/residual viable germ cell malignancy (GCM) is often challenging in patients with CSI on surveillance or with residual post-chemotherapy disease. The presence of a biomarker for GCM would overcome the uncertainty of the current methods and improve the quality of care of those patients. Methods: A 2-cohorts pilot study involving patients with clearcut evidence of GCM (clinical stage IS, metastatic and GCM prior orchiectomy) for the development cohort and patients with CSI with or without signs of tumor relapse and patients with metastatic GCM post-chemotherapy for the validation cohort. Blood samples collected in Streck tubes were obtained prior to chemotherapy for the development cohort and post-orchiectomy, at the time of suspicious relapse or post-chemotherapy in the validation cohort. Plasma miR-371a-3p (miR371) was analyzed by RT-PCR. Positive predictive value (PPV), sensitivity, specificity, negative predictive values (NPV) and AUC of the ROC for miR371 and standard diagnostic tools (CT scan, AFP, BHCG and LDH) were calculated correlating qualitative miR371 expression to the presence of viable GCM. Results: 132 patients were enrolled into the development (33 pts) and validation (99 pts) cohorts. Within the development cohort 31/33 pts were miR371 positive, 2/33 pts were negative. 31 true positives were found among the 31 miR371 positive patients for a PPV of 100% (31/31). Two true negatives were found among the 2 patients who had no miR371 expression identified (teratoma, lymphoma). The validation cohort was chosen to evaluate the methodology among patients with predicted lower volumes or no clinically apparent disease. 13/99 patients within the validation cohort were miR371 positive and all 13 had subsequent confirmation of viable GCM. For the overall study of 132 pts, PPV was 100% (46/46), NPV 98%, sensitivity 96% and specificity 100%, the AUC of the ROC was 0.96. Conclusions: Detectable circulating miR-371a-3p levels predict viable GCM and may represent a strategy for biological rather than radiographic assessment for surveillance of early stage and for post-treatment patients. Larger studies to validate these and like results have been planned.