RESUMO
<p><b>OBJECTIVE</b>To establish a new function method for the analysis of a-fetoprotein (AFP) and beta-hCG in testicular tumors.</p><p><b>METHODS</b>We reexamined the serum levels of AFP and beta-hCG after radical orchiectomy, and calculated the measured coordinate, with the abscissa representing the number of the half-lives of tumor markers, and the ordinate representing the measured value of tumor markers. Referring to the measured value of tumor markers before surgery as a, the number of half-lives as x, and their theoretical value over a period of x elimination half-lives as y (logarithm to the base 2 of y), we calculated the predicted coordinate according to the formula y = log2(a/2x) ==> x + y = log2a (function 1). Then we assessed tumor residue and metastasis by analyzing the relationship between the measured and predicted coordinates.</p><p><b>RESULTS</b>The pathological examination of case 1 revealed a germ cell tumor of a mixed histological pattern of syncytiotrophoblast and yolk sac tumor. The measured coordinates of AFP and beta-hCG were (2.22, 6.21) and (10, 8.38), and the predicted coordinates (2.22, 6.34) and (10, 4.41) , indicating the elimination of the yolk sac tumor and metastasis of the syncytiotrophoblast tumor. Case 2 demonstrated the mixed pathological nature of teratocarcinoma and yolk sac tumor. The measured coordinates of AFP and beta-hCG were (2.67, -1.03) and (12, -3.32), and the predicted coordinates (2.67, 1.41) and (12, -5.80). But the review times of AFP and beta-hCG were out of the effective range of half-lives, with the measured values below the normal, which suggested no tumor residue or metastasis. Case 3 was found to be embryonal carcinoma. The measured coordinate of AFP was (0.22, 9.25) , and the predicted coordinate (0.22, 9.55) , indicating the elimination of tumor.</p><p><b>CONCLUSION</b>The change of the tumor markers predicted by the function method coincided with the natural course of disease in the three cases. The coincidence of the measured with the predicted coordinate after radical orchiectomy indicates no metastasis, while their disagreement suggests possible residue and metastasis of the tumor.</p>