Predictive performance of TPA testing for recurrent disease during follow-up after curative intent surgery for colorectal carcinoma

Background: The aim of the present study was to investigate the predictive performance of serial tissue polypeptide antigen (TPA) testing after curative intent resection for detection of recurrence of colorectal malignancy. Methods: Serum samples were obtained in 572 patients from three different hospitals during follow-up after surgery. Test characteristics of serial TPA testing were assessed using a cut-off value of 75 U/L. The relation with American Joint Committee on Cancer stage and the potential additive value of tissue polypeptide antigen testing upon standard carcinoembryonic antigen (CEA) testing were investigated. Results: The area under the receiver operating characteristic curve of TPA for recurrent disease was 0.70, indicating marginal usefulness as a predictive test. Forty percent of cases that were detected by CEA testing would have been missed by TPA testing alone, whilst most cases missed by CEA were also not detected by TPA testing. In the subpopulation of patients with stage III disease predictive performance was good (area under the curve 0.92 within 30 days of diagnosing recurrent disease). In this group of patients, 86% of cases that were detected by CEA were also detected by TPA. Conclusions: Overall, TPA is a relatively poor predictor for recurrent disease during follow-up. When looking at the specific subpopulation of patients with stage III disease predictive performance of TPA was good. However, TPA testing was not found to be superior to CEA testing in this specific subpopulation.