Fig. 1.

CEA values (preoperative, postoperative day 7, postoperative day 30) over time (a). An exponential trend line was drawn using each CEA value. R² values were calculated as the deviation between calculated curves and the measured CEA value. The function of the exponential curve also was calculated (Y = pX^−q). The value “q” represents the gradient; it refers to the acute or slow decrease in CEA following tumor resection (b)