INDUCTION OF DISCRIMINANT FUNCTION CONCERNING POSTOPERATIVE LOCAL RECURRENCE OR DISTANT METASTASIS IN 589 PATIENTS WITH DIFFERENTIATED THYROID-CANCER

For the purpose of predicting postoperative local recurrence and/or di stant metastasis in differentiated thyroid cancer, a discriminant anal ysis was done. To assess the reliability of this method and the induce d function, simulation was done by using random samples under various conditions. Simulation revealed that the results obtained by this meth od were relatively stable. The discriminant functions Z1 and Z2 were i nduced, which are required at many hospitals. If the ratio of recurren ce is less than 1:8 in a hospital, function Z1 should be applied. If t he ratio is 1:10, function Z2 should be applied. Z1 = -(sex x 2.104) (age x 0.032) - (diameter of tumor x 0.033) - (site of tumor x 0.871) - (histology x 0.393) + 0.249 (discriminant boundary 0.451) Z2 = -(se x x 1.967) + (age x 0.018) + (diameter of tumor x 0.025) - (site of tu mor x 0.646) + (histology x 0.014) - (local invasion x 0.840) - (lymph node metastasis x 0.009) + (operation x 0.364) - (lymph node dissecti on x 0.235) + 1.058 (discriminant boundary 0.400) In an internal check , sensitivity was 78%, specificity 64%, and false-negative rate 5%. In an external check, sensitivity was 68%, specificity 93%, and false-ne gative rate 9%. In the actual application to hospitals, sensitivity wa s 58% to 100%, specificity 47% to 63%, and false-negative rate 0% to 1 6%. In clinical usage, a high sensitivity and low false-negative rate are required. These results fulfilled this condition.