Patient and Treatment Characteristics
In total, 51,917 patients were included in this study. There were 18,009 women diagnosed with ER+/HER2- BC, 3,325 with ER+/HER2+ BC, 7,958 with ER-/HER2+ BC, and 22,625 with TNBC (Table 1). The average age among the four cohorts was 53 years. The majority of patients were White, resided in a metropolitan/urban area, insured via private insurance, and had a Charlson Comorbidity Index (CCI) score of 0. Around half of the patients had AJCC clinical stage II vs stage III disease, and stage III disease was most prevalent in patients with TNBC (58.5%) while stage II disease most prevalent in the ER+/HER+ subtype (54.1%), p<0.001. The majority of patients presented with ductal histology and lobular histology was rare in ER- patients, and ER- patients were most commonly poorly differentiated.
Table 1. Demographic and clinical characteristics of patients with clinically node positive breast cancer receiving neoadjuvant chemotherapy, by subtype
Characteristics
|
TNBC
(n=22,625)
|
ER+/HER2+
(n=3,325)
|
ER+/HER2-
(n=18,009)
|
ER-/HER2+
(n=7,958)
|
P value
|
Age (median in years, interquartile range)a
|
53 (21-90)
|
53 (23-90)
|
53 (21-90)
|
54 (23-90)
|
<0.001
|
Race, no (%)
|
|
|
|
|
|
White
|
15,445 (72.3%)
|
2,532 (83.1%)
|
13,535 (81.0%)
|
5,883 (81.0%)
|
<0.001
|
Black
|
5,823 (27.3%)
|
500 (16.4%)
|
3,091 (18.5%)
|
1,356 (18.7%)
|
Other
|
90 (0.4%)
|
15 (0.5%)
|
83 (0.5%)
|
25 (0.3%)
|
Place of residence, no (%)
|
|
|
|
|
|
Metro/Urban
|
22,316 (98.6%)
|
3,280 (98.7%)
|
17,760 (98.6%)
|
7,855 (98.7%)
|
0.98
|
Rural
|
309 (1.4%)
|
45 (1.4%)
|
249 (1.4%)
|
103 (1.3%)
|
|
Insurance status, no (%)
|
|
|
|
|
|
Not insured
|
751 (3.3%)
|
103 (3.1%)
|
613 (3.4%)
|
270 (3.4%)
|
0.82
|
Insured
|
21,874 (96.7%)
|
3,222 (96.9%)
|
17,396 (96.6%)
|
7,688 (96.6%)
|
Treatment facility region, no (%)
|
|
|
|
|
|
South
|
8,262 (43.0%)
|
1,214 (42.6%)
|
6,704 (43.2%)
|
2,877 (41.5%)
|
0.53
|
Northeast
|
3,295 (17.1%)
|
546 (19.2%)
|
2,700 (17.4%)
|
1,327 (19.1%)
|
Midwest
|
4,864 (25.3%)
|
586 (20.6%)
|
3,581 (23.1%)
|
1,640 (23.7%)
|
West
|
2,809 (14.6%)
|
504 (17.7%)
|
2,542 (16.4%)
|
1,088 (15.7%)
|
Facility type, no (%)
|
|
|
|
|
|
Academic/Research
|
6,488 (33.7%)
|
910 (31.9%)
|
4,961 (32.0%)
|
2,209 (31.9%)
|
0.05
|
Community
|
8,383 (43.6%)
|
1,381 (48.5%)
|
7,080 (45.6%)
|
3,160 (45.6%)
|
Integrated Network
|
4,359 (22.7%)
|
559 (19.6%)
|
3,486 (22.5%)
|
1,563 (22.6%)
|
CCIa, no (%)
|
|
|
|
|
|
0
|
19,398 (85.7%)
|
2,925 (88.0%)
|
15,648 (86.9%)
|
6,919 (86.9%)
|
<0.001
|
1
|
2,534 (11.2%)
|
315 (9.5%)
|
1,846 (10.3%)
|
811 (10.2%)
|
>1
|
693 (3.1%)
|
85 (2.6%)
|
515 (2.9%)
|
228 (2.9%)
|
Clinical Stage, no (%)
|
|
|
|
|
<0.001
|
Stage 2
|
9,393 (41.5%)
|
1,800 (54.1%)
|
9,531 (52.9%)
|
4,028 (50.6%)
|
Stage 3
|
13,232 (58.5%)
|
1,525 (45.9%)
|
8,478 (47.1%)
|
3,930 (49.4%)
|
Histology, no (%)
|
|
|
|
|
|
Ductal
|
20,380 (90.1%)
|
2,896 (87.1%)
|
14,224 (79.0%)
|
7,174 (90.2%)
|
<0.001
|
Lobular
|
236 (1.0%)
|
104 (3.1%)
|
1,739 (9.7%)
|
87 (1.1%)
|
Infiltrating ductal
|
532 (2.4%)
|
176 (5.3%)
|
1,210 (6.7%)
|
223 (2.8%)
|
Other
|
1,477 (6.5%)
|
149 (4.5%)
|
836 (4.6%)
|
474 (6.0%)
|
Grade, no (%)
|
|
|
|
|
|
Well differentiated
|
132 (0.6%)
|
102 (3.4%)
|
1,268 (7.7%)
|
68 (0.9%)
|
<0.001
|
Moderately differentiated
|
2,706 (12.9%)
|
1,131 (37.9%)
|
7,701 (46.6%)
|
1,676 (23.3%)
|
Poorly differentiated
|
18,085 (86.4%)
|
1,752 (58.7%)
|
7,559 (45.7%)
|
5,453 (75.8%)
|
Type of surgery, no (%)
|
|
|
|
|
|
Partial mastectomy
|
8,169 (36.1%)
|
985 (29.7%)
|
5,076 (28.2%)
|
2,568 (32.3%)
|
|
Total mastectomy
|
14,402 (63.7%)
|
2,322 (70.0%)
|
12,890 (71.7%)
|
5,371 (67.6%)
|
None
|
32 (0.1%)
|
11 (0.3%)
|
24 (0.1%)
|
11 (0.1%)
|
<0.001
|
Lymph node surgery, no (%)
|
|
|
|
|
|
SLNBb only
|
6,247 (30.4%)
|
627 (22.7%)
|
3,273 (20.1%)
|
2,277 (31.5%)
|
<0.001
|
ALNDc only
|
10,464 (51.0%)
|
1,622 (58.8%)
|
8,911 (54.8%)
|
3,723 (51.5%)
|
SLNB and ALND
|
3,816 (18.6%)
|
508 (18.4%)
|
4,084 (25.1%)
|
1,224 (16.9%)
|
Radiation therapy, no (%)
|
|
|
|
|
|
No
|
4,469 (19.8%)
|
977 (29.4%)
|
3,106 (17.3%)
|
1,987 (25.0%)
|
<0.001
|
Yes
|
17,417 (77.0%)
|
2,184 (65.7%)
|
14,266 (79.2%)
|
5,683 (71.4%)
|
Unknown
|
739 (3.3%)
|
164 (4.9%)
|
637 (3.5%)
|
288 (3.6%)
|
a Charlson Comorbidity Index
b Sentinel lymph node biopsy
c Axillary lymph node dissection
The majority of patients (67.3%) underwent total mastectomy. Patients with TNBC were more likely to undergo partial mastectomy (36.1%) compared to patients with ER+/HER2- (28.2%) or ER+/HER2+ (29.7%) subtypes, p<0.001. In total, 23.9% of patients underwent sentinel lymph node biopsy (SLNB) without axillary dissection, and this was more commonly performed for the TNBC and ER-/HER2+ subtypes (30.4% and 31.5% respectively) compared to ER+/HER2+ (22.7%) and ER+/HER2- (20.1%). Adjuvant radiation therapy was delivered to the majority of patients, with the lowest delivery for ER+/HER2+ patients (65.7%).
Predictors of Mortality in Patients Receiving NAC for cN+ Breast Cancer
Adjusted associations between clinical and demographic factors and overall survival (OS) are listed in Table 2. After adjustment, there remained a significant association between age and Black race and mortality (Table 2). Insured patients were less likely to die (OR 0.82, 95% CI 0.70-0.97, p=0.02) compared to uninsured patients, and patients treated at a community hospital was associated with mortality (OR 1.11, 95% CI 1.04-1.19) compared to an academic/research institution. After adjustment, higher CCI, as well as both clinical stage and tumor grade, were associated with mortality. Mortality was associated with TNBC receptor subtype with overlapping OR for the remaining 3 receptor subtypes. ypN status was the strongest predictor of mortality in ypN3 patients (OR 8.85, 95% CI 7.88 – 9.33) compared to ypN0 patients.
Table 2. Adjusted logistic regression of factors associated with mortality among patients with clinically node-positive breast cancer after neoadjuvant chemotherapy
|
ORa
|
95% CIb
|
P Value
|
Age, in years
|
1.02
|
[1.02 – 1.03]
|
<0.001
|
Race (ref: white)
|
Black
|
1.17
|
[1.09 – 1.25]
|
<0.001
|
Other
|
1.40
|
[0.88 – 2.24]
|
0.16
|
Place of residence (Metro/Urban as reference)
|
Rural
|
1.17
|
[0.92 – 1.48]
|
0.20
|
Insurance status (Not insured as reference)
|
Insured
|
0.82
|
[0.70 – 0.97]
|
0.020
|
Treatment facility region (South as reference)
|
Northeast
|
0.94
|
[0.86 – 1.02]
|
0.12
|
Midwest
|
1.00
|
[0.93 – 1.07]
|
0.97
|
West
|
0.92
|
[0.84 – 1.01]
|
0.08
|
Facility type (Academic/Research as reference)
|
Community
|
1.11
|
[1.04 – 1.19]
|
0.003
|
Integrated Network
|
1.08
|
[1.00 – 1.17]
|
0.06
|
CCIc (0 as reference)
|
1
|
1.18
|
[1.08 – 1.29]
|
<0.001
|
>1
|
1.88
|
[1.60 – 2.20]
|
<0.001
|
Histology (Ductal as reference)
|
Lobular
|
1.20
|
[1.04 – 1.38]
|
0.011
|
Other
|
1.16
|
[1.05 – 1.27]
|
0.002
|
Grade (1 as reference)
|
2
|
1.49
|
[1.25 – 1.78]
|
<0.001
|
3
|
2.07
|
[1.73 – 2.46]
|
<0.001
|
Clinical stage (ref: stage 2)
Stage 3
|
1.72
|
[1.63 – 1.83]
|
<0.001
|
Subtype (ref: TNBCd)
ER+/HER2+
ER+/HER2-
ER-/HER2+
|
0.50
0.55
0.55
|
[0.44 – 0.57]
[0.51 – 0.59]
[0.50 – 0.61]
|
<0.001
<0.001
<0.001
|
ypN (ref: ypN0)
ypN1
ypN2
ypN3
|
2.24
5.03
8.85
|
[2.08 – 2.41]
[4.60 – 5.51]
[7.88 – 9.93]
|
<0.001
<0.001
<0.001
|
a Odds ratio
b Confidence interval
c Charlson comorbidity index
d Triple negative breast cancer
Long-Term Oncologic Outcomes Stratified by ypN status
Because nodal status was the strongest predictor of mortality, we performed KM analysis of overall survival stratified by ypN status for each receptor subtype. OS in patients with clinical positive lymph nodes after receiving NAC worsens with higher RNB for all subtypes. Specifically, for TNBC (Figure 1A), 5-year OS was 85% for patients with ypN0 disease and decreased with increasing residual nodal stage with 5-year OS of only 21% in patients with ypN3 disease, a 64% absolute difference. Similarly, a large absolute difference in 5-year OS was observed in the ER-/HER2+ subtype (Figure 1B), which was 91% in ypN0 patients and only 44% in ypN3 patients, a 47% absolute difference. In contrast, the absolute difference in 5-year OS was 28% between ypN0 and ypN3 patients with the ER+/HER2+ subtype (Figure 1C), and 25% (87% vs 62%) in patients with the ER+/HER2- subtype (Figure 1D).
Interaction of ypN status and Receptor Subtype on Survival
Stratification of KM curves by ypN stage was not uniform by receptor subtype, so we sought to more precisely delineate the interaction between post-treatment nodal stage and receptor subtype on overall survival. After adjustment for age, race, CCI, grade, and clinical stage, the impact of ypN stage on survival was assessed for each receptor subtype (Figure 2). The impact of ypN3 status (vs ypN0) was largest in the TNBC and ER-/HER2+ subtypes, OR 16.5 for TNBC and 9.6 for ER-/HER2+. The impact of increasing nodal stage on 5-year OS was least in the ER+/HER2- subtype.