Study Population Characteristics
Among 260 women who had undergone blood sampling for evaluation of Mastocheck® value and whole-breast US, we excluded 23 because of a personal history of breast cancer (n=1), recent surgical excision (n=5), and no follow-up for at least 12 months (n=17). Finally, 237 women (median age, 51 years; interquartile age range [IQR], 45-58 years) were included, and 59 (24.9%) healthy individuals (median age, 54 years; IQR, 47-60 years) and 178 (75.1%) breast cancer patients (median age, 51 years; IQR, 44-58 years) (Fig. 1). A total of 138 (58.2%, 138/237) women were asymptomatic, and 99 (41.8%, 99/237) had breast-related symptoms. A total of 192 (81.0%, 192/237) women had dense breasts, 41 (17.3%, 41/237) had fatty breasts on mammography, and 4 (1.7%, 4/237) had no available mammography. The characteristics of the study population are summarized in Table 1. Among 178 patients with breast cancer diagnosis, 142 (79.8%) had invasive ductal cancer, 11 (6.2%) invasive lobular cancer, 17 (9.5%) ductal carcinoma in situ, 3 (1.7%) mixed invasive ductal and lobular cancer, 2 (1.1%) mucinous carcinoma, 2 (1.1%) metaplastic carcinoma, and 1 (0.6%) intraductal papillary carcinoma. The mean size of 178 cancers was 1.2±0.8 cm (median, 1.5 cm; range, 0-4.0 cm). Most were stage I (50.6%, 90/178) and stage II (39.3%, 70/178). Benign lesions were fibroadenoma (n=2), intraductal papilloma (n=1); and follow-up imaging was performed for 56 lesions and were stable with a follow-up period of 13.5 months (range, 12.1-25.2 months).
Table 1
Baseline characteristics of the study patients
Parameter
|
Total (n=237)
|
Nonmalignant (n=59)
|
Malignant (n=178)
|
Age (years)
|
Median (Interquartile range)
|
51 (45-58)
|
54 (47-60)
|
51 (44-58)
|
Mammographic breast density
|
BI-RADS A or B, fatty
|
41 (17.3)
|
13 (22.0)
|
28 (15.7)
|
BI-RADS C or D, dense
|
192 (81.0)
|
42 (71.2)
|
150 (84.3)
|
Not available
|
4 (1.7)
|
4 (6.8)
|
0 (0.0)
|
Symptom
|
No
|
138 (58.2)
|
54 (91.5)
|
84 (47.2)
|
Yes
|
99 (41.8)
|
5 (8.5)
|
94 (52.8)
|
American Joint Committee on Cancer Stage
|
0
|
|
17 (9.5)
|
I
|
90 (50.6)
|
II
|
70 (39.3)
|
III
|
1 (0.6)
|
Histologic type
|
Ductal carcinoma in situ
|
|
17 (9.5)
|
Invasive ductal
|
142 (79.8)
|
Invasive lobular
|
11 (6.2)
|
Invasive ductal and lobular
|
3 (1.7)
|
Others
|
5 (2.8)
|
Note. —Data in parentheses indicate the percentages |
BI-RADS = Breast Imaging Reporting and Data System |
Assessment On Breast Us And Mastocheck®
The BI-RADS final assessment category and Mastocheck® values are listed in Table 2. On US, 98.9% (176/178) of malignant masses were assessed as test-positive, and 64.4% (38/59) of non-malignant lesions as test-positive. There were two (1.1%, 2/178) BI-RADS category 2 and two (1.1%, 2/178) BI-RADS category 3 breast cancers manifesting suspicious calcifications on mammography that were not visible on US. The results of Mastocheck® showed positive results with values higher than 0.0668 in 126 lesions (70.8%, 126/178) among breast cancer patients, whereas it showed negative results with values lower than 0.0668 in 46 lesions (78.0%, 46/59) in nonmalignant cases (P < .001). For nonmalignant lesions, the median value was -0.24 (IQR, -0.48, -0.03) and for malignant lesions, the median value was 0.55 (IQR, -0.03, 1.42) with significant difference (P < .001).
Table 2
Assessment on Mastocheck®, US, and Combined Mastocheck® with US
Parameter
|
Total (n=237)
|
Nonmalignant (n=59)
|
Malignant (n=178)
|
P value
|
US Assessment
|
<.001
|
Negative (BI-RADS Category 1, 2)
|
23 (9.7)
|
21 (35.6)
|
2 (1.1)
|
Positive (BI-RADS Category ≥3)
|
214 (90.3)
|
38 (64.4)
|
176 (98.9)
|
3
|
26 (11.0)
|
24 (40.7)
|
2 (1.1)
|
4A
|
35 (14.8)
|
14 (23.7)
|
21 (11.8)
|
4B
|
25 (10.5)
|
0 (0)
|
25 (14.0)
|
4C
|
34 (14.3)
|
0 (0)
|
34 (19.1)
|
5
|
94 (39.7)
|
0 (0)
|
94 (52.8)
|
Mastocheck® Value
|
<.001
|
Median (Interquartile range)
|
0.26 (-0.25, 1.13)
|
-0.24 (-0.48, -0.03)
|
0.55 (-0.03, 1.42)
|
Negative (value < 0.0668)
|
98 (41.4)
|
46 (78.0)
|
52 (29.2)
|
Positive (value ≥ 0.0668)
|
139 (58.6)
|
13 (22.0)
|
126 (70.8)
|
Combined Assessment*
|
<.001
|
Negative
|
40 (16.9)
|
38 (64.4)
|
2 (1.1)
|
Positive
|
197 (83.1)
|
21 (35.6)
|
176 (98.9)
|
Note. —Data in parentheses indicate the percentages |
BI-RADS = Breast Imaging Reporting and Data System |
*For combined assessment, BI-RADS category 3 or 4A masses are downgraded to BI-RADS category 2 or 3 if Mastocheck® value is less than 0.0668. |
Performance Of Mastocheck®, Us, And Combined Mastocheck® With Us
For breast US, with BI-RADS category of 3 or higher considered to be positive, the AUC of breast US alone was 0.67 (95%CI, 0.61, 0.73). Sensitivity, specificity, PPV, and NPV were 98.9% (95% CI: 97.3, 100.0), 35.6% (95% CI: 23.4, 47.8), 82.2% (95% CI: 77.1, 87.3), and 91.3% (95% CI: 79.8, 100.0), respectively. Mastocheck® showed AUC of 0.74 (95% CI, 0.68, 0.81), sensitivity of 70.8% (95% CI: 64.1, 77.5), specificity of 77.9% (95% CI, 67.4, 88.5), PPV of 90.6% (95% CI, 85.8, 95.5), and NPV of 46.9% (95% CI, 37.0, 56.8) (Table 3). By addition of Mastocheck® value to breast US assessment, the AUC was increased from 0.67 (95% CI, 0.61, 0.73) to 0.81 (95% CI 0.75, 0.88; P < .001), specificity was increased from 35.6% (95% CI: 23.4, 47.8) to 64.4% (95% CI: 52.2, 76.6; P < .001) without a loss in sensitivity (Fig. 2); PPV was also increased from 82.2% (95% CI: 77.1, 87.3) to 89.3% (95% CI: 85.0, 93.6; P < .001) (Fig. 3). The biopsy rate was significantly decreased from 79.3% (188/237) to 72.1% (171/237) (P < .001). By downgrading one category according to the Mastocheck® result showing lower value than 0.0668, the number of positive cases was decreased from 38 to 21 lesions (44.8% decrease) and 85.7% (12/14) of unnecessary biopsies for non-malignant lesions could be avoided (Fig. 4). Five cancers that were initially classified as BI-RADS category 4A on breast US were downgraded to BI-RADS category 3 with negative values on Mastocheck®. They were two 0.5-cm and 0.2-cm invasive ductal carcinoma, two 0.5-cm invasive lobular carcinoma, and one ductal carcinoma in situ (Table 4, Fig. 5).
Table 3
Diagnostic Performance of Mastocheck®, US, and Combined Mastocheck® with US
Parameter
|
Mastocheck®
|
US
|
Combined*
|
P value for Mastocheck® vs. US
|
P value for Mastocheck® vs. Combined
|
P value for
US
vs. Combined
|
AUC
|
0.74 (0.68, 0.81)
|
0.67 (0.61, 0.73)
|
0.81 (0.75, 0.88)
|
.104
|
.051
|
<.001
|
Sensitivity (%)
|
70.8 (64.1, 77.5) [126/178]
|
98.9 (97.3, 100) [176/178]
|
98.9 (97.3, 100) [176/178]
|
<.001
|
<.001
|
-
|
Specificity (%)
|
77.9 (67.4, 88.5) [46/59]
|
35.6 (23.4, 47.8) [21/59]
|
64.4 (52.2, 76.6) [38/59]
|
<.001
|
.042
|
<.001
|
PPV (%)
|
90.6 (85.8, 95.5) [126/139]
|
82.2 (77.1, 87.3) [176/214]
|
89.3 (85.0, 93.6) [176/197]
|
<.001
|
.692
|
<.001
|
NPV (%)
|
46.9 (37.0, 56.8) [46/98]
|
91.3 (79.8, 100.0) [21/23]
|
95.0 (88.2, 100) [38/40]
|
<.001
|
<.001
|
.491
|
Biopsy rate (%)
|
|
79.3 [188/237]
|
72.1 [171/237]
|
-
|
-
|
<.001
|
Note- Data in parentheses are 95% confidence intervals, and data in brackets are numerators and denominators. |
AUC = area under the curve; PPV = positive predictive value; NPV = negative predictive value. |
*For combined assessment, BI-RADS category 3 or 4A masses are downgraded to BI-RADS category 2 or 3 if Mastocheck® value is less than 0.0668. |
Table 4
Characteristics of Five Breast Cancers Downgraded by combined interpretation of breast US and Mastocheck® value
Patient
|
Age (years)
|
Symptom
|
MG density
|
MG BI-RADS
|
US BI-RADS
|
Mastocheck® value
|
Stage of cancer
|
Size (cm)
|
Histologic Type
|
Grade
|
Hormone receptor status
|
1
|
63
|
No
|
D
|
2
|
4A
|
-0.3800
|
I
|
0.5
|
Invasive ductal
|
Low
|
ER+/PR+/HER2-
|
2
|
51
|
No
|
B
|
1
|
4A
|
0.0564
|
I
|
0.5
|
Invasive lobular
|
Intermediate
|
ER+/PR+/HER2-
|
3
|
52
|
No
|
D
|
1
|
4A
|
-0.5943
|
I
|
0.5
|
Invasive lobular
|
Intermediate
|
ER+/PR+/HER2-
|
4
|
56
|
Palpable
|
D
|
3
|
4A
|
-0.7231
|
I
|
0.2
|
Invasive ductal
|
Intermediate
|
ER+/PR+/HER2-
|
5
|
53
|
No
|
D
|
4
|
4A
|
-1.1326
|
0
|
0.2
|
DCIS
|
Intermediate
|
ER+/PR+/HER2-
|
BI-RADS = Breast Imaging Reporting and Data System; DCIS = ductal carcinoma in situ; ER = estrogen receptor, HER2 = human epidermal growth factor receptor 2; MG = mammography; PR = progesterone receptor; US = ultrasound. |
Subgroup Analysis
To investigate whether the combined assessment showed similar performance in mimic screening setting, we performed subgroup analysis according to the presence of symptom and mammographic finding. In subgroup of 63 women with normal or benign mammographic findings, AUC of US was increased from 0.70 (95% CI: 0.62, 0.77) to 0.84 (95% CI: 0.77, 0.91; P < .001), specificity and PPV were also increased from 39.1 % (95% CI: 25.0, 53.2) to 67.4% (95% CI: 53.8, 80.9; P < .001) and from 37.8% (95% CI: 23.6, 51.9) to 53.1% (95% CI: 35.8, 70.4, P < .001), respectively, without loss of sensitivity with addition of Mastocheck® result. In 135 asymptomatic women, with the addition of Mastocheck® result, the AUC of US was increased from 0.66 (95% CI: 0.60, 0.73) to 0.81 (95% CI: 0.74, 0.88; P < .001), specificity and PPV were also increased from 35.3 % (95% CI: 22.2, 48.4) to 64.7% (95% CI: 51.6, 77.8; P < .001) and from 71.3% (95% CI: 63.0, 79.6) to 82.0% (95% CI: 74.5, 89.5, P < .001), respectively, without loss of sensitivity. The improvement in AUC, specificity, and PPV was consistently seen, 0.70 (95% CI: 0.63, 0.78) to 0.85 (95% CI: 0.77, 0.92), 40.5% (95% CI: 25.6, 55.3) to 69.1% (95% CI: 55.1, 83.0), and 37.5% (95% CI: 22.5, 52.5) to 53.6% (95% CI: 35.1, 72.0), respectively, in 57 asymptomatic women with normal or benign findings on mammographic examinations (all, P < .001) (Table 5, Supplementary Fig.).
Table 5
Diagnostic Performance of Mastocheck®, US, and Combined Mastocheck® with US in Subgroups According to Mammographic Finding and Associated Symptom
Parameter
|
Mastocheck®
|
US
|
Combined*
|
P value for Mastocheck® vs. US
|
P value for Mastocheck® vs. Combined
|
P value for
US
vs. Combined
|
Mammography normal/benign (n=63)
|
AUC
|
0.67 (0.54, 0.81)
|
0.70 (0.62, 0.77)
|
0.84 (0.77, 0.91)
|
0.782
|
0.020
|
<.001
|
Sensitivity (%)
|
58.8 (35.4, 82.2) [10/17]
|
100.0 (100.0) [17/17]
|
100.0 (100.0) [17/17]
|
-
|
-
|
-
|
Specificity (%)
|
76.1 (63.7, 88.4) [35/46]
|
39.1 (25.0, 53.2) [18/46]
|
67.4 (53.8, 80.9) [31/46]
|
<.001
|
0.201
|
<.001
|
PPV (%)
|
47.6 (26.3, 68.9) [10/21]
|
37.8 (23.6, 51.9) [17/45]
|
53.1 (35.8, 70.4) [17/32]
|
0.490
|
0.381
|
<.001
|
NPV (%)
|
83.3 (72.0, 94.6) [35/42]
|
100.0 (100.0) [18/18]
|
100.0 (100.0) [31/31]
|
0.490
|
0.381
|
<.001
|
Biopsy rate (%)
|
-
|
39.7 [25/63]
|
23.8 [15/63]
|
|
|
<.001
|
Asymptomatic (n=135)
|
AUC
|
0.75 (0.68, 0.82)
|
0.66 (0.60, 0.73)
|
0.81 (0.74, 0.88)
|
0.073
|
0.155
|
<.001
|
Sensitivity (%)
|
67.8 (57.8, 77.8) [57/84]
|
97.6 (94.4, 100.0) [82/84]
|
97.6 (94.4, 100.0) [82/84]
|
<.001
|
<.001
|
-
|
Specificity (%)
|
82.3 (71.9, 92.8) [42/51]
|
35.3 (22.2, 48.4) [18/51]
|
64.7 (51.6, 77.8) [33/51]
|
<.001
|
0.010
|
<.001
|
PPV (%)
|
86.4 (78.0, 94.6) [57/66]
|
71.3 (63.0, 79.6) [82/115]
|
82.0 (74.5, 89.5) [82/100]
|
<.001
|
0.273
|
<.001
|
NPV (%)
|
60.8 (49.3, 72.4) [42/69]
|
90.0 (76.9, 100.0) [18/20]
|
94.3 (86.6, 100.0) [33/35]
|
<.001
|
<.001
|
0.084
|
Biopsy rate (%)
|
-
|
68.2 [92/135]
|
57.0 [77/135]
|
|
|
<.001
|
Asymptomatic and Mammography normal/benign (n=57)
|
AUC
|
0.70 (0.56, 0.85)
|
0.70 (0.63, 0.78)
|
0.85 (0.77, 0.92)
|
0.976
|
0.058
|
<.001
|
Sensitivity (%)
|
60.0 (35.2, 84.8) [9/15]
|
100.0 (100.0) [15/15]
|
100.0 (100.0) [15/15]
|
-
|
-
|
-
|
Specificity (%)
|
80.9 (69.1, 92.8) [34/42]
|
40.5 (25.6, 55.3) [17/42]
|
69.1 (55.1, 83.0) [29/42]
|
<.001
|
0.090
|
<.001
|
PPV (%)
|
52.9 (29.2, 76.7) [9/17]
|
37.5 (22.5, 52.5) [15/40]
|
53.6 (35.1, 72.0) [15/28]
|
0.302
|
0.764
|
<.001
|
NPV (%)
|
85.0 (73.9, 96.0) [6/40]
|
100.0 (100.0) [17/17]
|
100.0 (100.0) [29/29]
|
0.302
|
0.764
|
<.001
|
Biopsy rate (%)
|
|
38.6 [22/57]
|
21.1 [12/57]
|
|
|
<.001
|
Note- Data in parentheses are 95% confidence intervals, and data in brackets are numerators and denominators. |
AUC = area under the curve; PPV = positive predictive value; NPV = negative predictive value; US = ultrasound. |
*For combined assessment, BI-RADS category 3 or 4A masses are downgraded to BI-RADS category 2 or 3 if Mastocheck® value is less than 0.0668. |