HER2 in gastric cancer: Comparative analysis of three different antibodies using whole-tissue sections and tissue microarrays

Table 1 Results of HER2 immunostaining using the three antibodies on whole-tissue sections and tissue microarrays n (%)

Score	Whole-tissue sections			TMAs
	HercepTest	4B5	SP3	HercepTest	4B5	SP3
0	179 (90.9)	125 (63.1)	128 (65.2)	185 (93.5)	174 (88.8)	162 (82.6)
1+	7 (3.5)	30 (15.2)	17 (8.5)	3 (1.5)	10 (5.1)	8 (4.1)
2+	1 (0.5)	20 (10.1)	34 (17.2)	4 (2.0)	3 (1.5)	15 (7.7)
3+	10 (5.1)	23 (11.6)	18 (9.1)	6 (3.0)	9 (4.6)	11 (5.6)
Total	197 (100.0)	198 (100.0)	197 (100.0)	198 (100.0)	196 (100.0)	196 (100.0)

TMA: Tissue microarray.

Table 2 Concordance between the tissue microarrays and whole-tissue sections staining results using the HercepTest, 4B5 and SP3 antibodies

Antibody	Overall concordance	Kappa coefficient (95%CI)
HercepTest	97.40%	0.75 (0.54-0.96)
4B5	84.10%	0.38 (0.22-0.53)
SP3	85.60%	0.56 (0.43-0.70)

Table 3 Human epidermalgrowth factor receptor 2 gene status assessed by dual-color in situ hybridization in cases with an immunohistochemistry score of 2+ with HercepTest, 4B5 and SP3 staining on whole-tissue sections and tissue microarrays n (%)

HER2gene status	Whole-tissue sections			TMAs
	HercepTest	4B5	SP3	HercepTest	4B5	SP3
Amplified	0 (0)	6 (30)	6 (17.6)	3 (75)	3 (100)	4 (26.6)
Not amplified	1 (100)	14 (70)	28 (82.4)	1 (25)	0 (0)	11 (73.4)
Total	1 (100)	20 (100)	34 (100)	4 (100)	3 (100)	15 (100)

TMA: Tissue microarray; HER2: Human epidermalgrowth factor receptor 2.

Table 4 Specificity, sensitivity, positive and negative predictive values and the area under the receiver operating characteristic curve of each antibody according to the final human epidermalgrowth factor receptor 2 status

		HercepTest (95%CI)	4B5 (95%CI)	SP3 (95%CI)
TMA	Sensitivity	42.9 (21.7-64.0)	57.1 (35.9-78.3)	66.7 (46.5-86.8)
	Specificity	99.4 (98.3-100.0)	100.0	93.1 (89.4-96.9)
	PPV	90.0 (71.4-100.0)	100.0	53.8 (34.7-73.0)
	NPV	93.6 (90.1-97.1)	95.1 (92.0-98.2)	95.9 (92.9-98.9)
	AUC	0.71 (0.60-0.782)	0.79 (0.68-0.89)	0.80 (0.69-0.90)
Whole-tissue sections	Sensitivity	47.6 (26.2-68.9)	95.2 (86.1-100.0)	90.5 (77.9-100.0)
	Specificity	99.4 (98.3-100.0)	87.0 (82.0-91.9)	81.2 (75.5-87.0)
	PPV	90.9 (73.9-100.0)	46.5 (31.6-61.4)	36.5 (23.4-49.6)
	NPV	94.1 (90.7-97.5)	99.3 (98.1-100.0)	98.6 (96.7-100.0)
	AUC	0.73 (0.63-0.84)	0.91 (0.86-0.96)	0.86 (0.78-0.93)

PPV: Positive predictive value; NPV: Negative predictive value; AUC: Area under the receiver operating characteristic curve; TMA: Tissue microarray.

Table 5 Accuracy of the three antibodies in the whole-tissue sections and the tissue microarrays

		HercepTest	4B5	SP3
Whole-tissue sections	AUC	0.73	0.91	0.78
	HercepTest	-	P = 0.002	P = 0.035
	4B5	P = 0.002	-	P = 0.265
	SP3	P = 0.035	P = 0.265	-
TMAs	AUC	0.71	0.79	0.8
	HercepTest	-	P = 0.058	P = 0.075
	4B5	P = 0.058	-	P = 0.714
	SP3	P = 0.075	P = 0.714	-

AUC: Area under the receiver operating characteristic curve; TMA: Tissue microarray.

Table 6 Comparison of the areas under the receiver operating characteristic curve according to the type of sample (whole-tissue section and tissue microarray) and the antibodies

		Whole-tissue sections
			HercepTest	4B5	SP3
		AUC	0.73	0.91	0.78
TMAs	HercepTest	0.71	P = 0.572	P = 0.001	P = 0.013
	4B5	0.79	P = 0.289	P = 0.027	P = 0.201
	SP3	0.80	P = 0.265	P = 0.034	P = 0.244

AUC: Area under the receiver operating characteristic curve; TMA: Tissue microarray.