Abstract
We investigated whether the early postoperative time course of carcinoembryonic antigen (CEA) level after resection of lung cancer could be used to predict patients' prognosis. Fifty-three lung cancer patients were included in this study. Postoperative serum CEA levels were calculated by means of non-linear least-squares fitting to the equation C(t) = (C(0)-C(p))exp(-kt) + C(p), where C(t) is postoperative CEA level, t is days after surgery, C(0) is CEA level at postoperative time 0, C(p) is CEA level at plateau, and k is the rate constant of elimination. Postoperative CEA production (P(p)) was calculated as C(p) multiplied by k. C(p) and P(p) represent the numbers of residual tumor cells after surgery. More residual tumor cells yield higher values of C(p) and P(p), and result in earlier recurrence. RESULTS: Kinetic parameters could be obtained for 30 patients whose preoperative CEA levels were sufficiently elevated. Cutoff levels as predictors for recurrence were 1.1 ng/ml for C(p) and 0.9 ng/ml/day for P(p). The accuracy of prediction of recurrence using these cutoff levels was 79% with C(p) and 89% with P(p). A very poor prognosis was observed for patients with P(p) over 0.9 ng/ml/day. CONCLUSION: Analysis of the time course of changes in CEA levels after resection of lung cancer appears to be useful for predicting patient prognosis. C(p) and P(p) are very precise predictors of recurrence.