Free β-Subunit of Human Chorionic Gonadotropin in Serum Is a Diagnostically Sensitive Marker of Seminomatous Testicular Cancer

BACKGROUND: We studied whether measurement of the free beta subunit of human chorionic gonadotropin (hCGbeta) in serum offers additional diagnostic information compared to determination of intact hCG alone in testicular cancer. METHODS: We determined hCG and hCGbeta with ultrasensitive assays in 94 serum samples obtained preoperatively, 22 samples obtained during relapse, and 3687 samples obtained during routine follow-up of 351 patients with testicular tumors. RESULTS: In preoperative samples, isolated increases of hCGbeta were seen in 40% of the samples from seminoma patients (n = 42) and in 8% of those from patients with nonseminomatous testicular cancer (NSGCT) (n = 51). Both markers were increased in 12% of the seminoma and 71% of the NSGCT patients and were within reference intervals in 43% of the seminoma and 20% of the NSGCT patients. Specific determination of hCGbeta increased the frequency of marker-positive seminomas from 17% to 57% and of marker-positive relapses from 32% to 59% (n = 22). Theoretically, about 40% of marker-positive seminomas and relapses would have been missed with an assay measuring hCG and hCGbeta together. Preoperative hCG and hCGbeta concentrations correlated with stage, tumor histology, and disease-related mortality. Additionally, hCGbeta correlated with tumor size. CONCLUSIONS: hCGbeta is a diagnostically sensitive marker for testicular cancer. In patients with seminomatous testicular cancer, hCGbeta is superior to hCG, and in some NSGCT patients it provides additional information.