The value of AFP and HCG half lives in predicting the efficacy of combination chemotherapy in patients with non-seminomatous germ cell tumors of the testis

The decline of serum levels of AFP or HCG in 26 patients with disseminated non-seminomatous germ cell tumors during chemotherapy showed two different patterns: a linear decline or an increasing apparent half life (AHL). The initial AFP half life in 13 patients with a linear decline was 7.2 ± 1.8 days, and did not differ from the initial half life in 5 patients with a curvi-linear pattern. HCG half life was 3.0 ± 0.5 days in 10 patients with a linear AHL, and was not different from the initial half life in 6 patients with delayed marker disappearance. Based on the half life pattern of AFP or HCG the result of chemotherapy was predicted. When AFP or HCG showed a linear decline, all viable tumor appeared to be eliminated in 38 and 40% respectively of the patients. An increasing AHL indicated the presence of active tumor, mostly mature teratoma, in 60% of the patients with AFP and in 83% of the patients with HCG. Thus, the pattern of AFP or HCG half life does not predict the eventual outcome of chemotherapy with certainty.