AUA 2022: Refinement of the Serum miR-371a-3p Test for the Detection of Chemotherapy-naive Minimal Residual Testicular Cancer

( In a moderated poster presentation at the 2022 American Urologic Association Annual Meeting held in New Orleans and virtually, Dr. Aditya Bagrodia presented work refining the role of serum microRNA (miR)-371a-3p in advanced testis cancer. Currently clinically utilized serum biomarkers, while forming an important basis of risk stratification and patient monitoring, have relatively poor performance for the detection of testicular germ cell tumors (GCTs). In contrast, while still in the realm of research, serum miRNAs, particularly miR-371a-3p, have demonstrated excellent performance characteristics in the pre-orchiectomy setting. Whether miR-371a-3p is useful to detect occult disease is understudied. In this presentation, the authors expand on their prior work.

Using a cohort of chemotherapy-naïve GCT patients undergoing primary retroperitoneal lymph node dissection (RPLND), the authors prospectively collected clinical information and pre-surgical serum samples. Patients were classified as “Control” (pure teratoma or no GCT) or “GCT”. RNA was extracted from these serum samples, and miR-371a-3p (target) and miR-30b-5p (reference gene) were detected by qPCR. They examined over 250 distinct runs to compare performance between classification based on Cq, normalized Cq (∆Cq), or relative quantification (RQ). The test performance characteristics of miR-317a-3p was assessed by calculation of sensitivity, specificity, and area under the ROC curve (AUC).

Interestingly, test performance did not change appreciably when thresholding based on Cq, ∆Cq, or RQ. As a result, they opted to utilize an analysis considering only Cq. Notably, for quality control purposes, found that any given control sample returned a spurious positive result approximately 25% of the time. Therefore, to improve test characteristics, they estimated an indeterminate range of Cq 28-35. For patients with results in this range, repeating testing once improved overall performance. The authors then compared this updated process to a simple binary threshold in a cohort of patients with occult disease.

They utilized 32 patients of whom 15 acted as control and 17 had active GCT. 12 samples were indeterminate on first run, and 8 remained indeterminate on a second run, all of which harbored viable GCT or teratoma. Inclusion of a second run prevented 3 false positives, improving specificity from 86% to 100% and yielding a sensitivity of 92% and AUC of 0.96 (95% CI: 0.89-1).

Thus, the authors conclude that the use of Cq instead of RQ to classify results for the miR-371a-3p test helps to avoid unnecessary sample runs without injuring assay performance. In the context of chemotherapy-naïve minimal residual testicular cancer, consideration of an indeterminate range may improve the performance of the miR-371a-3p test.

Presented by: Aditya Bagrodia, MD, UC San Diego Health

Written by: Christopher J.D. Wallis, University of Toronto Twitter: @WallisCJD during the 2022 American Urological Association (AUA) Annual Meeting, New Orleans, LA, Fri, May 13 – Mon, May 16, 2022.