Comparison between free β subunit of human chorionic gonadotropin (hCG) and total hCG assays in adults with testicular cancer

Abstract

We tested the hypothesis that the free-β subunit (βhCG) is diagnostically more sensitive with total hCG assays (hCGt) not detecting all tumours secreting βhCG. The effects of sex, age, and renal failure were investigated as secondary objectives. We compared βhCG with hCGt in 204 testicular cancer patients (99 seminomas, 105 non-seminonatous germ cell tumours). The effects of sex and age were determined in 125 male and 138 female controls and that of renal failure was investigated in 119 haemodialysis patients. Biochemical assessment of gonadal status was performed with LH, FSH, oestradiol and testosterone. Discordant results were common with isolated increases of hCGt observed in 32 (15.7 %) and βhCG in 14 (6.9 %) patients. Primary hypogonadism was the most common cause of isolated hCGt increases. After therapeutic interventions βhCG decreased below its upper reference more rapidly than hCGt. We observed unequivocal false negative results in two patients with non-seminomatous germ cell tumours. Both occurred in patients with clinical tumour recurrences; in one instance we observed a false negative hCGt while in the second false negative βhCG's were documented in serial samples. The similar false negative rates did not support the hypothesis that βhCG will detect more patients with testicular cancer than hCGt. In contrast to hCGt, βhCG was unaffected by primary hypogonadism which is a predictably frequent complication in testicular cancer patients. We therefore recommend βhCG as the preferred biomarker in testicular cancer.