Table 2.

Accuracy to predict response to gefitinib according to the method used to evaluate EGFR expression

Methods of evaluationBest cutoffSensitivitySpecificityAccuracyPPVNPVLRAUCP
Subset of 70 patients
Specific antibodies for the ED of EGFR
ED IHC membraneNANA (%)NA (%)NA (%)NA (%)NA (%)NA0.540.6038
ED IHC membrane and cytoplasm2553.355.855.225.880.61.210.540.6197
ED AQUA8.4853.368.665.236.483.31.700.660.0653
Specific antibody for the internal domain of EGFR
ID IHC membrane23553.37570.138.184.82.130.700.0289
ID IHC membrane and cytoplasm21566.769.268.738.587.82.170.730.0078
ID AQUA12.7253.88679.45087.83.850.780.0018
Whole cohort of 98 patients
Specific antibodies for the ED of EGFR
ED IHC membraneNANANANANANANA0.580.2643
ED IHC membrane and cytoplasm37.552.464.461.729.782.51.470.590.1763
Specific antibody for the internal domain of EGFR
ID IHC membrane20552.469.965.933.383.61.740.640.0484
ID IHC membrane and cytoplasm21766.774.072.342.488.52.560.720.0016

NOTE: To compare the performance of the techniques/antibodies to discriminate responders versus nonresponders, this table displays the results with the 70 patients on which the 6 different evaluations have been carried out. In addition, data on the total cohort are reported for IHC.

Abbreviations: NA, no accuracy for both a sensitivity and specificity of at least 50%; LR, likelihood ratio; AUC, area under the curve; P, P value for the AUC.