Current and Evolving Biomarkers in the Diagnosis and Management of Testicular Germ Cell Tumors.

Testicular cancer is the most common cancer among young adult men and has favorable outcomes, with survival rates approaching 99% and over 80% for those with early and advanced stage disease, respectively. Biomarkers play a critical role in the diagnosis, pre-treatment risk stratification, surveillance, and assessment of post-treatment disease response in these men. Traditional serum tumor markers (STMs), which include alpha fetoprotein (AFP), beta subunit of human chorionic gonadotropin (β-hCG), and lactate dehydrogenase (LDH), are limited by low sensitivity (approximately 50%) during initial diagnosis; false-positive elevations as a result of other benign and malignant conditions; and negative levels in low-stage disease and in certain histologies such as teratoma and seminoma. As a result, novel biomarkers with potentially better performance characteristics, including microRNA (miRNA), circulating tumor DNA (ctDNA), and circulating tumor cells (CTCs), are being investigated. MicroRNAs are small noncoding RNA involved in transcription and translation and regulate the expression of almost one-third of human genes that regulate the cell cycle, differentiation, proliferation, and apoptosis. In germ cell tumor (GCT) patients, miR371a-3p has been identified as a promising biomarker with sensitivity and specificity of approximately 90-92% and 84-86%, respectively. The use of this new biomarker could aid in several clinical scenarios, such as predicting the presence of micrometastases in chemotherapy-naïve patients with clinical stage I-II disease, thereby guiding decisions on treatment versus surveillance and predicting the presence of viable GCT in patients with residual disease post chemotherapy. Clinical trials are ongoing to validate the use of miRNA 371 as a biomarker and to define its performance characteristics. Though promising, miRNAs are limited by their inability to detect teratoma. ctDNA and CTCs are two other emerging biomarkers, though further studies are needed to clarify their role in managing patients with GCT.