Clinical evaluation of the role of miRNA 371 in small testicular masses. Results of the "S1STeM 371" Trial.

Objective: Incidental small testicular masses (STMs) pose the dilemma of invasive Vs surveillance. To test miRNA 371 kit (M371, CE approved) in predicting germ cells tumor (GCT) in patients with STM.

Methods: Thirty-two consecutive men with a STM between 5 and 20 mm have been prospectively accrued. All patients had miRNA 371 blood testing before surgery. Serum miRNA processation was standardized and certified and following transcription into cDNA with an endogeneous control. The Relative Quantity (RQ) was determined by quantitative polymerase chain reaction (qPCR) following preamplification. Different RQ cut-offs were tested. The results of pre-surgery 371 miRNA were compared to definitive pathology.

Results: Median lesion size was 14 mm (IQR 8-18 mm). 21 of 32 patients (65.6 %) had GCTs: 14 seminomatous (S)GCTs, 6 non-seminomatous (NS)GCTs, 1 in-situ germ cell neoplasia (GCNIS). Median RQ was 57.50 (IQR 18.50, 223.75) among GCT patients and 5.00 (IQR 1.00, 13.50) in patients without GCTs. We tested for sensitivity (SE), specificity (SP), positive (PPV) and negative predictive value (NPV) at different RQ cut-offs of 5 and 10. SE, SP, PPV and NPV were 100 %, 45 %, 78.1 %, 100 % 95.2 %, 63.7 %, 83.6 %, 87.3 %, respectively.

Conclusions: Serum miRNA 371 can predict GCTs in selected patients with 5-20 mm STM. These results need to be refined by standardizing the analytical process.