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Alpha‐fetoprotein half‐life as a predictor of residual testicular tumor. Effect of the analytic strategy on test sensitivity and specificity
Author(s) -
See William A.,
Cohen Michael B.,
Hoxie Logan D.
Publication year - 1993
Publication title -
cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/1097-0142(19930315)71:6<2048::aid-cncr2820710620>3.0.co;2-r
Subject(s) - medicine , testicular cancer , residual , orchiectomy , alpha fetoprotein , positive predicative value , nuclear medicine , oncology , cancer , predictive value , mathematics , algorithm , hepatocellular carcinoma
Background . Alpha‐fetoprotein (AFP) serum values after orchiectomy for testicular cancer can be used to predict the residual disease status. However, the optimal strategy for postorchiectomy marker analysis has not been studied. This article evaluated different analytic methods in an effort to identify the approach that provided the greatest sensitivity and specificity for occult residual disease. Methods . Statistical information on the AFP half‐life (t 1/2 ) derived from a clinical data set of 24 patients with AFP‐secreting clinical Stage A testicular cancer and pathologically defined nodal status was incorporated into a mathematic model of postorchiectomy marker values as a function of residual tumor volume and time. The model was used to test the effect of various analytic strategies on detecting the residual tumor. The clinical data set then was analyzed to measure the effect of different analytic methods on the predictive value of the AFP t 1/2 . Results . In the model, the AFP t 1/2 calculated from a single set of serum measurements obtained from the initial serum t 1/2 was a poor predictor of disease status in patients with up to 40% residual tumor volume. Determined by the sequential addition of serum values obtained at normal t 1/2 intervals, the AFP t 1/2 improved in sensitivity but required up to seven serial values (35 days) to detect an abnormal t 1/2 in patients with 10% residual tumor. By contrast, changes in the most recent interval t 1/2 relative to the initial calculated t 1/2 predicted the disease status in patients with 10% residual tumor after four t 1/2 (20 days) and in patients with 1% residual volume after 35 days. Conclusions . The use of this last strategy in the clinical data set improved both the sensitivity and specificity of the AFP t 1/2 in predicting residual tumor relative to the other methods.