1. Clinical characteristics
Clinical and pathologic characteristics are shown in Table 1. Sixty-eight patients had BRCA1 mutations while 60 patients had BRCA2 mutations. Patients with BRCA mutations had a significantly younger age of onset than that of control patients (BRCA vs. control: 43.9 vs. 52.5 years-old, p < 0.001). Additionally, molecular types between BRCA and non-BRCA patients were significantly different (p < 0.001); a higher proportion of BRCA mutation patients than non-BRCA patients had TNBC (BRCA vs. control: 52.3% vs. 12.0%), followed by the ER(+) Her2(-) patients (41.4% vs. 61.3%). A small proportion of BRCA patients had ER(+) Her2(+) breast cancer (5.5% vs. 11.1%), and none of them had pure Her2 type cancer (0 vs. 10.4%). When stratified by genotype, 76% (n = 56) of BRCA1 patients had TNBC whereas 66.7% (n = 40) of BRCA2 patients had ER(+) Her2(-) breast cancer.
Table 1
Patient and tumor characteristics according to germline BRCA status.
Characteristics
|
BRCA mutated (n = 128)
|
BRCA1 mutated
(n = 68)
|
BRCA2 mutated (n = 60)
|
BRCA non-mutated (n = 4754)
|
BRCA vs. non-BRCA
p value
|
Age (years, mean ± SD)
|
43.9 ± 10.1
|
42.4 ± 10.2
|
45.6 ± 9.8
|
53.2 ± 11.6
|
< 0.001
|
Molecular type
|
|
|
|
|
< 0.001
|
ER(+)Her2(-)LuminalA
|
37
|
8
|
29
|
1813
|
|
ER(+)Her2(-)LuminalB
|
16
|
5
|
11
|
793
|
|
ER(+)Her2(+)
|
7
|
3
|
4
|
470
|
|
Her2(+)
|
0
|
0
|
0
|
456
|
|
TNBC
|
67
|
52
|
15
|
514
|
|
unknown
|
1
|
0
|
1
|
704
|
|
Disease status of diagnosis
|
|
|
|
|
|
(de novo) stage IV
|
4
|
3
|
1
|
250
|
0.185
|
Stage 0-III
|
|
|
|
|
|
T classification
|
|
|
|
|
0.713
|
T0
|
2
|
1
|
1
|
154
|
|
T1
|
58
|
33
|
25
|
1919
|
|
T2
|
51
|
27
|
24
|
2029
|
|
T3-4
|
10
|
3
|
7
|
402
|
|
unknown
|
4
|
2
|
2
|
0
|
|
N classification (post)
|
|
|
|
|
0.814
|
N0
|
75
|
43
|
32
|
2767
|
|
N1
|
25
|
13
|
12
|
1078
|
|
N2
|
12
|
4
|
8
|
408
|
|
N3
|
7
|
3
|
4
|
210
|
|
unknown
|
6
|
3
|
3
|
0
|
|
Second malignancies (not Breast cancer)
|
|
|
|
|
< 0.001
|
Positive
|
20
|
10
|
10
|
238
|
< 0.001
|
Ovarian cancer
|
17
|
9
|
8
|
8
|
< 0.001
|
Other cancers
|
3
|
2
|
1
|
230
|
< 0.001
|
There were no difference in the distributions of tumor size and LN status between BRCA and non-BRCA mutation patients. BRCA mutation patients had a significantly higher risk of developing second non-breast cancer (p < 0.001). The main second malignancy was ovarian cancer, whose incidence was similar between BRCA1 and BRCA2 patients. For the 17 patients with ovarian cancer, twelve (70.6%) of them developed ovarian cancer after breast cancer and 5 cases had ovarian cancer before breast cancer. The types of the second malignancy for the control cases were significantly different from that of BRCA patients; the most common cancer of the control patients was lung cancer (p < 0.001).
2. Relapse-free And Overall Survival
The median follow time was 4.67 (range 0.1 to 22.9) years. Kaplan-Meier analysis revealed that relapse-free survival (RFS) for patients with stage 0 to III breast cancer was similar between BRCA and control patients (Fig. 1A, p = 0.967). The RFS for BRCA patients was 85.2% (95% confidence interval (CI) 92.2% – 78.1%) at five years and 78.5 % (95% CI 87.5% – 69.5 %)at 10 years. On the other hand, the RFS for control patients was 86.2% (95% CI 87.4%-85.0%) and 79.0% (95% CI 80.8% – 77.2%) at 5 and 10 years, respectively. When stratified by BRCA1 and BRCA2 genotyping, the 10-year RFS for BRCA1 patients was 82.6% (95% CI 71.2% – 93.9%) whereas the RFS for BRCA2 patients was 74.4% (95 CI 60.1% – 88.3%). There was no significant difference in RFS between BRCA1, BRCA2 and control patients (Fig. 1B).
The prognostic factors for RFS in both BRCA and control patients were the tumor size and LN classification (Figs. 1C – 1F). Large tumor sizes and advanced LN classification resulted in poor RFS. When stratified by molecular types, the control patients with ER(+) Her2(-)LuminalA breast cancer had the best RFS out of all other types of breast cancer. Patients with ER(-)Her2(+) breast cancer had the worst RFS (Fig. 1G). For BRCA mutation carriers, patients with TNBC had a better RFS trend than those with other types of breast cancer (Fig. 1H), probably because most TNBC patients had stage I breast cancer.
Among the entire cohort, tumor size, LN classification and molecular types were independent risk factors for RFS (Table 2). Thus, we analyzed the impact of BRCA after adjusting for these major prognostic factors in a multivariable model; the results showed no difference in RFS between BRCA and control patients (HR = 1.071, 95% CI 0.689–1.664, Table 2). In contrast, large tumor size, advanced LN status, ER(+) Her2(-)LuminalB, ER(-) Her2(+) and TNBC remained the independent prognostic factors for RFS. Similarly, there was no difference in the overall survival (OS) between BRCA and control patients (HR = 0.721, 95% CI = 0.396–1.314). The tumor size, LN classification and molecular types were the independent risk factors of OS. Compared to patients with ER(+) Her2(-)LuminalA, patients with ER(+) Her2(-)LuminalB, ER(-)Her2(+) or TNBC had a significantly inferior OS (Table 3).
Table 2
Univariate and multivariate analysis of relapse-free survival
Clinical
|
Univariate
|
Multivariate
|
Characteristics
|
HR
|
lower
|
upper
|
P
|
HR
|
lower
|
upper
|
P
|
Tumor size
|
|
|
|
|
|
|
|
|
T0-1
|
reference
|
|
|
|
reference
|
|
|
|
T2
|
2.653
|
2.180
|
3.228
|
< 0.001
|
1.864
|
1.516
|
2.291
|
< 0.001
|
T3-4
|
5.594
|
4.370
|
7.160
|
< 0.001
|
3.387
|
2.590
|
4.428
|
< 0.001
|
LN
|
|
|
|
|
|
|
|
|
N0
|
reference
|
|
|
|
reference
|
|
|
|
N1
|
2.124
|
1.748
|
2.582
|
< 0.001
|
2.131
|
1.732
|
2.622
|
< 0.001
|
N2
|
4.234
|
3.426
|
5.231
|
< 0.001
|
3.732
|
2.966
|
4.695
|
< 0.001
|
N3
|
6.976
|
5.474
|
8.891
|
< 0.001
|
4.914
|
3.747
|
6.445
|
< 0.001
|
Molecular type
|
|
|
|
|
|
|
|
|
ER(+)Her2(-)LuminalA
|
reference
|
|
|
|
reference
|
|
|
|
ER(+)Her2(-)LuminalB
|
1.399
|
1.138
|
1.720
|
0.001
|
1.302
|
1.053
|
1.610
|
0.015
|
ERHer2(+)
|
1.380
|
1.060
|
1.798
|
0.017
|
1.017
|
.770
|
1.345
|
0.903
|
Her2(+)
|
1.885
|
1.478
|
2.405
|
< 0.001
|
1.573
|
1.218
|
2.032
|
0.001
|
TNBC
|
1.276
|
.990
|
1.643
|
0.060
|
1.304
|
1.001
|
1.699
|
0.049
|
Genotyping
|
|
|
|
|
|
|
|
|
non-BRCA
|
reference
|
|
|
|
reference
|
|
|
|
BRCA
|
0.991
|
0.647
|
1.517
|
0.967
|
1.071
|
0.689
|
1.664
|
0.761
|
Table 3
Multivariate analysis of overall survival
Clinical
|
Multivariate
|
Characteristics
|
HR
|
lower
|
upper
|
P
|
Tumor size
|
|
|
|
|
T0-1
|
reference
|
|
|
|
T2
|
1.686
|
1.318
|
2.157
|
< 0.001
|
T3-4
|
2.503
|
1.753
|
3.576
|
< 0.001
|
LN
|
|
|
|
|
N0
|
reference
|
|
|
|
N1
|
1.859
|
1.440
|
2.400
|
< 0.001
|
N2
|
3.170
|
2.390
|
4.204
|
< 0.001
|
N3
|
3.996
|
2.818
|
5.665
|
< 0.001
|
Molecular type
|
|
|
|
|
ER(+)Her2(-)LuminalA
|
reference
|
|
|
|
ER(+)Her2(-)LuminalB
|
1.729
|
1.338
|
2.235
|
< 0.001
|
ER(+)Her2(+)
|
1.107
|
0.759
|
1.615
|
0.598
|
ER(-)Her2(+)
|
1.537
|
1.084
|
2.180
|
0.016
|
TNBC
|
1.681
|
1.203
|
2.348
|
0.002
|
Genotyping
|
|
|
|
|
non-BRCA
|
reference
|
|
|
|
BRCA
|
0.721
|
0.396
|
1.314
|
0.286
|
Multivariate model include tumor size, LN, molecular type and genotyping |
3. Risk Of Contralateral Breast Cancer
The risk of contralateral breast cancer (CBC) was significantly higher in BRCA mutation patients than in control cases (HR = 3.950, 95% CI 2.712–5.752, p < 0.001.. The CBC risk was 26.0% (95% CI 16.0% – 36.0%) at 10 years and 44.0% (95% CI 27.1% – 60.8%) at 15 years in BRCA mutation patients, compared to 6.6% (95% CI 5.6% – 7.6%) at 10 years and 10.4% (95% CI 8.2% – 12.6%) at 15 years in control patients (Fig. 2A). When stratified y BRCA1 and BRCA2 genotyping, both patient groups had a significantly increased risk of CBC in comparison to control patients (BRCA1: HR = 4.844, 95% CI 3.001–7.820, p < 0.001; BRCA2: HR = 3.130, 95% CI 1.782–5.498, p < 0.001). We then classified patients by molecular types; both ER(+) and TNBC BRCA mutation patients had a significantly higher risk of getting CBC than control patients with ER(+) breast cancer and TNBC, respectively (Figs. 2C and 2D).
Unlike RFS, tumor size, LN classification and molecular type did not affect the risk of CBC. BRCA mutation was the only independent risk factor of developing CBC in the analysis of the overall patients.
4. Characteristics of CBC risk in BRCA mutation carriers
Previous studies reported that patients younger than 40 years old had a higher risk of having CBC [9], so we divided patients into two groups: people at or younger than 40 years-old and people older than 40 years-old. However, the CBC risk was similar between BRCA patients younger and older than 40 years old (Fig. 3A). We found that there was a higher trend of CBC risk in BRCA1 mutation patients (HR = 1.814, 95% CI 0.865–3.805, p = 0.115) compared to that of BRCA2 mutation carriers. Similarly, TNBC patients had a higher trend of developing CBC than ER(+) BRCA patients (HR = 1.657, 95% CI 0.778–3.530, p = 0.185, Fig. 3B). When genotype and molecular types were integrated, BRCA1 patients with TNBC had the highest risk of CBC compared to other BRCA mutation patients (Fig. 3C and 3D). The CBC risk of BRCA1 patients with TNBC was 39.3% (95% CI 19.9% – 58.7%) and 63.6% (95% CI 39.0% – 88.1%) at 10 and 15 years, respectively. In comparison to the control patients, BRCA1 patients with TNBC had a greater than five-fold risk of developing CBC (HR = 5.550, 95% CI 3.295–9.349, p < 0.001).
Figure 3 Cumulative incidence of CBC in patients among BRCA mutation. The x-axis is followup time (years) and y-axis is cumulative incidence of CBC. (A) Risk of CBC by age onset of the first breast cancer (Less or equal to 40 year-old vs. more than 40 year-old. (B) Risk of CBC by ER(+) vs. TNBC (C) Risk of CBC by between different genotype and molecular type. (D) Risk of CBC by BRCA1 with TNBC vs. others.</fig>
5. Relationship Between Survival And Cbc
For the entire cohort, patients with and without CBC had a similar RFS (HR = 0.760, 95% CI 0.540–1.070) and OS (HR = 0.864, 95% CI 0.597–1.251). For the 128 BRCA mutation patients, 22 patients relapsed; 2 patients relapsed before CBC and 20 patients relapsed after CBC. For all patients with CBC, the 5-year RFS after CBC was 86.9% (95% CI 82.0% – 91.8%).