Longer follow-up data of circulating miR371a-3p expression across the spectrum of germ cell tumors (GCT).

Abstract

379 Background: miR371a-3p (miR371) is overexpressed in seminoma (S) and nonseminoma (NS) active germ cell malignancy (aGCM) and easily detectable in blood. We previously described1 a remarkably high accuracy of miR371 in detecting aGCM in early and advanced stages germ cell tumor (GCT) patients (pts). We here present the updated miR371 expression data with a longer follow-up, particularly relevant to assess miR371 clinical utility to predict GCT relapse in clinical stage I (CSI) and stage IIA pts. Methods:119 samples from 99 pts enrolled in the GU biobank program at the British Columbia Cancer – Vancouver were analyzed. The pts were divided according to their risk of aGCM in low (CSIA NS and CSI S), moderate (CSIB NS, stage IIA markers negative/low elevated S and NS), and high risk (definitively metastatic aGCM) groups. Blood of the low and moderate risk pts was collected post orchiectomy and at the time of the clinical relapse; prior to/post-chemotherapy in the high risk group. Plasma miR371 expression was evaluated by RT-PCR and quantified by ΔΔCT method. Sensitivity, specificity, negative and positive predictive values (NPV, PPV) and AUC of the ROC curve were analyzed. Results: Five (2 moderate - 3 low risks) pts were lost at follow-up and 1 high risk pt had deceased. Overall, 113 samples (50, 36, 27 in the low, moderate, and high risk groups, respectively) were analyzed. The median follow-up from study entry was 30 (6-51), 28 (20-52), and 29 (7-53) months for the low, moderate and high risk, respectively. Seven more relapses occurred: 4 in the low risk (3 S and 1 NS) and 3 in the moderate risk groups (2 NS and 1 S). miR371 was found falsely negative post-orchiectomy in 4 pts and truly negative in 3 relapsed pts (2 pure teratoma and 1 unconfirmed relapse). Serial analysis of the false negative relapsed pts showed that miR371 became detectable at the time of clinical relapse. The operating characteristics of miR371 are summarized in the table below. Conclusions: Our follow-up has exceeded the expected time of relapse even in the low risk pts. The high accuracy of miR371 in detecting aGCM was confirmed with a longer follow up. However, the few false negatives in relapsed pts and the serial analysis suggest a lack of sensitivity in the detection of microscopic disease post-orchiectomy with the current methodology while miR371 high sensitivity was confirmed in presence of radiologic measurable disease (≥ 1 cm). The definitive operating characteristics of miR371 post-orchiectomy and during the follow-up of stages I/ IIA pts will be prospectively validated by the S1823 study that is actively recruiting pts. [Table: see text]