Serum levels of microRNA-371a-3p (M371) for prediction of histology in chemotherapy-naïve patients with testicular germ cell tumours undergoing lymph node dissection—a retrospective analysis of 57 cases

BACKGROUND: Serum levels of microRNA-371a-3p (M371) represent a novel serum tumour marker of testicular germ cell tumours (GCTs). Little is known about its utility for assessing regional lymph nodes in chemotherapy-naïve patients. We measured M371 levels before lymphadenectomy (LND) and correlated expression rates with histologic findings. METHODS: Fifty-seven chemotherapy-naïve patients had M371 measurements before LND. Median M371 levels and M371 expression rates were compared across the postoperative histological subgroups of seminoma [SE], vital nonseminoma [VN], teratoma [TE], no malignancy tumour [pN0], and controls, between subgroups of tumour sizes, and between pre- and postoperative levels. M371 performance characteristics were calculated, including receiver operating characteristic curves. RESULTS: M371 levels were elevated in 17 (85%) of 20 patients with SE at LND, 16 (100%) with VN, none in 13 with TE, and 1 in 8 with pN0. The sensitivity, specificity, positive predictive value, and area under the curve of the M371 test for identifying lymph node metastases was 67.3%; 87.5%; 97.1%; 0.833, respectively, and 60.6%; 100%; 100%; 0.884 in VN, and 81.3%; 50%; 92.9%; 0.656 in SE. In SE cases, frequency and extent of M371 level elevation were significantly associated with the size of metastases. Postoperatively, M371 serum levels significantly decreased in VN and SE. CONCLUSIONS: Elevated M371 levels are predictive for lymph node metastases in 100% and in 92% of patients with primary testicular nonseminomas and SEs, respectively. TE does not express M371. Small volume SE is detected in only 50% of cases. Despite weaknesses, the test can aid in diagnosing marker-negative lymphadenopathies in GCTs.