Development and validation of a survival-predicting nomogram for HER2-negative T1–3N0–1 breast cancer treated with breast-conserving surgery: a Surveillance, Epidemiology, and End Results (SEER) database analysis
Original Article

Development and validation of a survival-predicting nomogram for HER2-negative T1–3N0–1 breast cancer treated with breast-conserving surgery: a Surveillance, Epidemiology, and End Results (SEER) database analysis

Sirui Zhu1, Wei Lu1, Ke Zhang1, Huaiyu Yang1, Chenxuan Yang1, Changyuan Guo2, Lei Guo2, Xuemin Xue2, Zhongzhao Wang1, Lixue Xuan1

1Department of Breast Surgical Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China; 2Department of Pathology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Contributions: (I) Conception and design: S Zhu, W Lu; (II) Administrative support: K Zhang, H Yang; (III) Provision of study materials or patients: C Yang, C Guo; (IV) Collection and assembly of data: L Guo, X Xue; (V) Data analysis and interpretation: Z Wang, L Xuan; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

Correspondence to: Lixue Xuan, PhD. Department of Breast Surgical Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 17 Panjiayuan Nanli, Chaoyang District, Beijing 100021, China. Email: xuanlx@hotmail.com.

Background: Human epidermal growth factor receptor 2 (HER2)-negative early-stage breast cancer (BC) exhibits significant heterogeneity, complicating personalized treatment decisions after breast-conserving surgery (BCS). Robust tools integrating baseline risk, treatment response, and sociodemographic factors are needed to optimize survival while minimizing unnecessary toxicity. This study aimed to create a clinical decision-support tool that leverages these multifaceted factors to optimize survival outcomes and minimize treatment toxicity for these patients.

Methods: Utilizing population-level data from the Surveillance, Epidemiology, and End Results (SEER) program (cases from 2010 to 2016; n=8,384), we constructed and validated prognostic nomograms for overall survival (OS) and cancer-specific survival (CSS) in a cohort of HER2-negative, T1–3N0–1 BC patients who underwent BCS followed by radiotherapy. Key prognostic variables were identified through multivariable Cox proportional hazards regression. The performance of the nomograms was rigorously assessed using the concordance index (C-index), time-dependent receiver operating characteristic (ROC) analysis, calibration curves, and decision curve analysis (DCA). Finally, risk stratification was performed by applying optimal cut-off points determined via X-tile software.

Results: Key independent predictors included tumor grade, tumor (T) stage, estrogen receptor (ER)/progesterone receptor (PR) status, marital status, and single primary tumor status. Nomograms significantly outperformed American Joint Committee on Cancer (AJCC) 7th staging (OS C-index: 0.69 vs. 0.63; CSS C-index: 0.74 vs. 0.63). Patients were stratified into low- (33%), middle-, and high-risk (27%) groups. Chemotherapy provided no OS/CSS benefit in low-risk patients but substantially improved outcomes in high-risk patients (P<0.001). Achieving a complete response (CR) following neoadjuvant chemotherapy (NAC) was associated with superior survival outcomes, particularly among high-risk patients, whereas a non-complete response (NCR) was linked to worse survival.

Conclusions: We developed the first validated nomograms integrating tumor biology, treatment response, and social factors to optimize HER2-negative BC management. Identifying ‘single primary tumor’ status as a novel prognostic indicator point to novel tumorigenesis mechanisms. Critically, our findings enable actionable strategies: low-risk patients (33%) may be candidates for avoiding chemotherapy toxicity, while high-risk patients (27%) are potential candidates for more intensive treatment strategies. Patients who fail to achieve a CR should be considered for enrollment in adjuvant trials with novel agents. Adding prospective biomarkers will further refine these precision approaches.

Keywords: Breast cancer (BC); human epidermal growth factor receptor 2-negative (HER2-negative); Surveillance, Epidemiology, and End Results (SEER); nomogram


Submitted Jul 11, 2025. Accepted for publication Dec 08, 2025. Published online Feb 11, 2026.

doi: 10.21037/gs-2025-301


Highlight box

Key findings

• We developed validated nomograms integrating tumor biology, treatment response, and sociodemographic factors to predict survival in human epidermal growth factor receptor 2 (HER2)-negative early breast cancer (BC) patients after breast-conserving surgery (BCS).

• These models outperformed traditional staging and stratified patients into low-, middle-, and high-risk groups.

• Chemotherapy provided no survival benefit in low-risk patients but was crucial for high-risk patients.

• Achieving a pathological complete response (CR) to neoadjuvant chemotherapy (NAC), especially in high-risk patients, was linked to excellent outcomes.

What is known and what is new?

• HER2-negative BC is heterogeneous, requiring better tools for personalized therapy after BCS.

• This study provides the first validated tool specifically for this T1–3N0–1 population, introduces “single primary tumor” as a novel prognostic factor, and dynamically integrates treatment response with baseline factors for risk assessment.

What is the implication, and what should change now?

• This tool can guide treatment: low-risk patients may avoid chemotherapy, while high-risk patients should be prioritized for NAC. Failure to achieve CR after NAC indicates a need for alternative strategies.

• Our findings advocate for a shift towards response-adapted, risk-stratified management. Prospective validation is the recommended next step.


Introduction

Breast carcinoma remains the predominant malignancy diagnosed among women worldwide and constitutes a leading cause of cancer-associated mortality (1). Breast-conserving surgery (BCS) combined with radiotherapy is the cornerstone of treatment for early-stage breast cancer (BC), offering excellent oncologic control and preserved quality of life for patients with T1–3N0–1 disease (2). Within this population, human epidermal growth factor receptor 2 (HER2)-negative tumors represent the most common molecular subtype, yet exhibit significant biological heterogeneity, leading to variable clinical outcomes (3,4). While patients with low-risk features may derive minimal benefit from systemic chemotherapy, those with high-risk clinicopathological factors—such as larger tumor size (T2–3), high histological grade, elevated Ki-67 index, or limited lymph node involvement—face a substantially increased risk of recurrence and mortality, making chemotherapy a critical component of their multimodal management (5-7).

Importantly, the efficacy of chemotherapy, particularly when administered preoperatively (neoadjuvant chemotherapy; NAC), varies markedly across this spectrum. Patients achieving a complete response (CR) following NAC demonstrate significantly improved long-term survival compared to those with residual disease (non-CR) (8,9). This prognostic dichotomy is especially pronounced in aggressive HER2-negative subtypes like triple-negative breast cancer (TNBC), where CR is strongly associated with excellent event-free survival (10,11). Conversely, failure to achieve CR, particularly in high-risk subgroups, identifies a cohort with persistent micrometastatic burden and a heightened need for intensified adjuvant strategies or novel therapeutic approaches (12). Furthermore, the degree of residual disease burden post-NAC provides refined prognostic stratification beyond the binary CR/non-CR distinction (13).

Despite standardized surgical and radiation approaches, the inability to consistently predict which patients will derive maximal benefit from chemotherapy or achieve CR hampers optimal personalized treatment selection for HER2-negative T1–3N0–1 BC patients undergoing BCS. Consequently, robust tools integrating baseline risk factors and dynamic response assessments are urgently needed to guide therapeutic decision-making, optimize survival outcomes, and spare low-risk patients from unnecessary toxicity. Several prognostic models and nomograms have indeed been developed for HER2-negative BC, including those utilizing the Surveillance, Epidemiology, and End Results (SEER) database. For instance, existing models predict survival in hormone receptor (HR)-positive/HER2-negative patients with axillary lymph node metastasis or guide adjuvant chemotherapy decision. These contributions are valuable; however, a systematic consideration of the literature reveals specific limitations in the context of our target population (14). Many existing models either focus on all surgical types collectively or are not specifically designed and validated for the distinct T1–3N0–1 population undergoing BCS. Furthermore, few integrate the dynamic assessment of treatment response with baseline tumor biology and sociodemographic factors into a single, practical tool for this specific cohort.

Consequently, a critical gap remains in consistently predicting which patients with HER2-negative T1–3N0–1 BC undergoing BCS will derive maximal benefit from chemotherapy or achieve a pathological complete response. This hampers optimal personalized treatment selection. Therefore, robust tools that uniquely combine baseline risk stratification with dynamic response assessments are needed to guide therapeutic decision-making, optimize survival outcomes, and spare low-risk patients from unnecessary toxicity.

To address this gap, our study aims to develop and validate prognostic nomograms for overall survival (OS) and cancer-specific survival (CSS) specifically within this well-defined cohort. The novelty of our model lies in its unique combination of predictors—integrating baseline clinicopathological variables, treatment response to NAC, and sociodemographic factors—tailored expressly for HER2-negative T1–3N0–1 patients treated with BCS, thereby facilitating more personalized adjuvant therapy decisions. We present this article in accordance with the TRIPOD reporting checklist (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-301/rc).


Methods

Data collection and patient selection

Based on the SEER Research Plus Data 22 registry [2000–2019], we initially identified female patients diagnosed with BC. To align with the consistent application of the 7th edition American Joint Committee on Cancer (AJCC) staging criteria, the study period was restricted to cases diagnosed between January 2010 and December 2016. Key inclusion criteria were: (I) HER2-negative status; (II) treatment with BCS followed by postoperative radiotherapy; and (III) tumor, node, metastasis (TNM) stage T1–3N0–1M0. Eligible cases were randomly split into training and internal validation sets at a 7:3 ratio. For each patient, demographic, clinicopathological, and treatment-related variables were extracted, including age at diagnosis, race, tumor laterality, AJCC TNM stage, histological grade, primary site, histology, lymph node involvement, estrogen receptor (ER) status, progesterone receptor (PR) status, HER2 status, tumor size, BC subtype, and sequence of tumor occurrence. Information on neoadjuvant therapy receipt, cause-specific death classification, and survival months (with a minimum of >0 days) was also collected. Patients with incomplete survival or follow-up records, or with zero or missing survival time, were excluded from the final analysis. The resulting cohort enabled robust evaluation of long-term survival and identification of independent prognostic factors. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Variable selection

The analysis incorporated the following variables: age at diagnosis, race, laterality, TNM stage, grade, tumor location, histological type, lymph node metastasis, BC subtype, tumor size, ER status, PR status, HER2 status, cause-specific death, tumor sequence, and response to neoadjuvant therapy. In accordance with the SEER database classification, several variables were consolidated into specific categories for analysis.

Age was categorized into two groups: <45 years and ≥70 years. Race was grouped as White and other. The primary tumor site was divided into five categories: lower-inner, lower-outer, upper-inner, upper-outer, and others. Tumor grade was classified as I/II versus III/IV. Histological type included infiltrating duct carcinoma and others. Laterality was designated as left or right. Marital status was grouped as married or unmarried. Chemotherapy use was classified as no/unknown or yes. Both PR and ER status were defined as negative or positive. The sequence number of tumors was categorized as one primary only or more than one primary. Tumor stage was classified into stages I, II, and IIIA. T stage was grouped as T1, T2, and T3, while N stage was categorized as N0 and N1.

Furthermore, a CR was defined as the absence of invasive cancer in both the breast (ypT0/Tis) and lymph nodes (ypN0) in the pathologic assessment following NAC, as recorded in the corresponding SEER fields. Any other outcome was classified as “non-CR”. A “single primary tumor” (one primary only) was defined as the first and only malignant tumor in the patient’s lifetime, as per the SEER sequence number code ‘00’. Any code indicating multiple tumors was categorized accordingly.

Statistical analysis

Prognostic factors were identified through univariate Cox proportional hazards regression and then assessed in a multivariate model. This analysis provided hazard ratios along with 95% confidence intervals (CIs) for each variable, ensuring robust identification of independent predictors.

Based on the multivariate Cox regression model implemented in R, we constructed and validated nomograms to estimate 1-, 3-, and 5-year OS and CSS. Model discrimination was assessed using the concordance index (C-index) and time‑dependent receiver operating characteristic (ROC) curves, with performance further quantified by the area under the curve (AUC). Calibration plots compared predicted versus observed survival. Clinical utility was assessed via decision curve analysis (DCA), quantifying net benefits across threshold probabilities. The development cohort was segmented into risk groups based on total points, and survival differences were analyzed using the Kaplan-Meier method with log-rank tests. Propensity score matching (PSM) was applied to evaluate clinical intervention effects on outcomes. Statistical analyses used R (v3.6.1) and SPSS (v25.0; IBM). The “rms”, “survival”, “magick”, “timeROC”, “ggplotify”, and “cowplot” R packages facilitated nomogram development and validation. Statistical significance was defined as P<0.05. All P values are from two-sided tests.


Results

Baseline clinical features

In summary, this study included 8,384 operable BC patients, categorized into a training cohort of 5,869 and an internal test cohort of 2,515 (Figure S1). The majority of patients (77.8% training, 78.1% test) were aged ≥45 years. All patients underwent BCS, with approximately two-thirds receiving chemotherapy (64.2% training, 65.4% test). Most tumors were moderately/well differentiated (grade I/II: 66.0% training, 66.3% test), while poorly differentiated/undifferentiated tumors (grade III/IV) accounted for 34.0% and 33.7% respectively. Infiltrating duct carcinoma was the predominant histologic subtype (77.0% training, 77.4% test). The HR+/HER2 subtype represented the vast majority of cases (85.2% training, 86.7% test), with ER positivity observed in 84.6% and 85.7% of cases, and PR positivity in 74.7% and 75.9% across cohorts. For tumor staging, stage II was most frequent (62.7% training, 63.5% test), with T2 being the commonest T stage (41.5% both cohorts) and N1 predominating in nodal status (51.3% training, 53.5% test). Baseline characteristics of the study population are summarized in Table 1. Pearson’s Chi-squared tests indicated no statistically significant differences in the distribution of clinicopathological features between the training and validation cohorts (all P>0.05).

Table 1

Baseline characteristics of operable breast cancer patients in training and test sets

Characteristic Training cohort (n=5,869) Internal test cohort (n=2,515) P value
Age 0.76
   <45 years 1,301 (22.2) 550 (21.9)
   ≥45 years 4,568 (77.8) 1,965 (78.1)
Race 0.38
   Others 1,332 (22.7) 549 (21.8)
   White 4,537 (77.3) 1,966 (78.2)
Primary site 0.92
   Lower-inner 351 (6.0) 161 (6.4)
   Lower-outer 567 (9.7) 236 (9.4)
   Others 2,001 (34.1) 864 (34.4)
   Upper-inner 714 (12.2) 297 (11.8)
   Upper-outer 2,236 (38.1) 957 (38.1)
Grade 0.75
   I/II 3,872 (66.0) 1,668 (66.3)
   III/IV 1,997 (34.0) 847 (33.7)
Histology 0.67
   Infiltrating duct carcinoma 4,519 (77.0) 1,947 (77.4)
   Others 1,350 (23.0) 568 (22.6)
Laterality 0.86
   Left 2,933 (50.0) 1,262 (50.2)
   Right 2,936 (50.0) 1,253 (49.8)
Chemotherapy 0.26
   No/unknown 2,102 (35.8) 869 (34.6)
   Yes 3,767 (64.2) 1,646 (65.4)
Breast subtype 0.06
   HR/HER2 867 (14.8) 334 (13.3)
   HR+/HER2 5,002 (85.2) 2,181 (86.7)
PR status 0.25
   Negative 1,486 (25.3) 607 (24.1)
   Positive 4,383 (74.7) 1,908 (75.9)
ER status 0.30
   Negative 901 (15.4) 360 (14.3)
   Positive 4,968 (84.6) 2,155 (85.7)
Sequence number 0.12
   More primaries 1,247 (21.2) 572 (22.7)
   One primary only 4,622 (78.8) 1,943 (77.3)
Marital status 0.65
   Married 3,645 (62.1) 1,575 (62.6)
   Unmarried 2,224 (37.9) 940 (37.4)
Stage 0.37
   I 1,619 (27.6) 659 (26.2)
   II 3,680 (62.7) 1,598 (63.5)
   IIIA 570 (9.7) 258 (10.3)
T stage 0.67
   T1 2,354 (40.1) 990 (39.4)
   T2 2,437 (41.5) 1,044 (41.5)
   T3 1,078 (18.4) 481 (19.1)
N stage 0.07
   N0 2,856 (48.7) 1,170 (46.5)
   N1 3,013 (51.3) 1,345 (53.5)

Data are presented as n (%). ER, estrogen receptor; HER2, human epidermal growth factor receptor 2; HR, hormone receptor; N, node; PR, progesterone receptor; T, tumor.

Variable feature importance of survival prediction

We systematically evaluated prognostic factors for OS and CSS in the training cohort. Candidate variables from univariate Cox regression analyses were integrated into multivariate models to identify independent predictors, with full results detailed across Tables 2-5.

Table 2

Univariate Cox analysis for OS of patients

Characteristic Number of patients Event number HR 95% CI P value
Age
   <45 years 1,301 130
   ≥45 years 4,568 596 1.33 1.10–1.61 0.003
Race
   Others 1,332 169
   White 4,537 557 0.97 0.82–1.15 0.73
Grade
   I/II 3,872 377
   III/IV 1,997 349 1.86 1.61–2.15 <0.001
Histology
   Infiltrating duct carcinoma 4,519 563
   Others 1,350 163 0.96 0.81–1.15 0.69
Laterality
   Left 2,933 376
   Right 2,936 350 0.93 0.80–1.07 0.32
Chemotherapy
   No/unknown 2,102 282
   Yes 3,767 444 0.85 0.74–0.99 0.03
ER status
   Negative 947 201
   Positive 4,922 525 0.47 0.40–0.56 <0.001
PR status
   Negative 1,486 287
   Positive 4,383 439 0.48 0.42–0.56 <0.001
Sequence number
   More primaries 1,247 223
   One primary only 4,622 503 0.64 0.54–0.75 <0.001
Marital status
   Married 3,645 357
   Unmarried 2,224 369 1.76 1.52–2.03 <0.001
T stage
   T1 2,354 217
   T2 2,437 336 1.71 1.44–2.02 <0.001
   T3 1,078 173 2.10 1.72–2.57 <0.001
N stage
   N0 2,856 376
   N1 3,013 350 1.02 0.88–1.18 0.82
Stage
   I 1,619 163
   II 3,680 472 1.52 1.27–1.82 <0.001
   IIIA 570 91 2.06 1.59–2.66 <0.001

CI, confidence interval; ER, estrogen receptor; HR, hazard ratio; N, node; OS, overall survival; PR, progesterone receptor; T, tumor.

Table 3

Multivariate Cox analysis for OS of patients

Characteristic Number of patients Event number HR 95% CI P value
Age
   <45 years 1,301 130
   ≥45 years 4,568 596 1.33 1.09–1.61 0.005
Grade
   I/II 3,872 377
   III/IV 1,997 349 1.71 1.43–2.05 <0.001
ER status
   Negative 947 201
   Positive 4,922 525 0.72 0.57–0.92 0.009
PR status
   Negative 1,486 287
   Positive 4,383 439 0.67 0.54–0.83 <0.001
Sequence number
   More primaries 1,247 223
   One primary only 4,622 503 0.56 0.47–0.66 <0.001
Marital status
   Married 3,645 357
   Unmarried 2,224 369 1.62 1.40–1.88 <0.001
T stage
   T1 2,354 217
   T2 2,437 336 1.72 1.29–2.29 <0.001
   T3 1,078 173 1.90 1.34–2.68 <0.001
Stage
   I 1,619 163
   II 3,680 472 1.10 0.80–1.50 0.55
   IIIA 570 91 1.41 0.91–2.19 0.12
Chemotherapy
   No/unknown 2,102 282
   Yes 3,767 444 0.59 0.49–0.70 <0.001

CI, confidence interval; ER, estrogen receptor; HR, hazard ratio; OS, overall survival; PR, progesterone receptor; T, tumor.

Table 4

Univariate Cox analysis for CSS of patients

Characteristic Number of patients Event number HR 95% CI P value
Age
   <45 years 1,266 100
   ≥45 years 4,306 327 0.95 0.76–1.18 0.63
Race
   Others 1,242 93
   White 4,330 334 1.05 0.83–1.32 0.71
Primary site
   Lower-inner 360 33
   Lower-outer 530 48 1.02 0.65–1.58 0.95
   Others 1,845 149 0.90 0.61–1.31 0.57
   Upper-inner 698 42 0.65 0.41–1.02 0.06
   Upper-outer 2,139 155 0.81 0.55–1.17 0.26
Grade
   I/II 3,622 184
   III/IV 1,950 243 2.52 2.08–3.05 <0.001
Histology
   Infiltrating duct carcinoma 4,290 324
   Others 1,282 103 1.06 0.85–1.33 0.60
Laterality
   Left 2,772 219
   Right 2,800 208 0.93 0.77–1.13 0.47
Chemotherapy
   No/unknown 1,913 104
   Yes 3,659 323 1.61 1.29–2.00 <0.001
ER status
   Negative 898 150
   Positive 4,674 277 0.34 0.28–0.41 <0.001
PR status
   Negative 1,413 207
   Positive 4,159 220 0.34 0.28–0.41 <0.001
Sequence number
   More primaries 1,144 115
   One primary only 4,428 312 0.74 0.60–0.92 0.007
Marital status
   Married 3,526 234
   Unmarried 2,046 193 1.44 1.19–1.74 <0.001
Stage
   I 1,511 72
   II 3,502 286 1.99 1.54–2.58 <0.001
   IIIA 559 69 3.26 2.34–4.54 <0.001
T stage
   T1 2,223 99
   T2 2,314 207 2.23 1.75–2.83 <0.001
   T3 1,035 121 3.12 2.39–4.06 <0.001
N stage
   N0 2,643 191
   N1 2,929 236 1.26 1.04–1.52 0.01

CI, confidence interval; CSS, cancer-specific survival; ER, estrogen receptor; HR, hazard ratio; N, node; PR, progesterone receptor; T, tumor.

Table 5

Multivariate Cox analysis for CSS of patients

Characteristic Number of patients Event number HR 95% CI P value
Grade
   I/II 3,622 184
   III/IV 1,950 243 1.70 1.35–2.14 <0.001
Chemotherapy
   No/unknown 1,913 104
   Yes 3,659 323 0.89 0.70–1.14 0.36
ER status
   Negative 898 150
   Positive 4,674 277 0.70 0.52–0.94 0.01
PR status
   Negative 1,413 207
   Positive 4,159 220 0.55 0.42–0.71 <0.001
Sequence number
   More primaries 1,144 115
   One primary only 4,428 312 0.57 0.46–0.71 <0.001
Marital status
   Married 3,526 234
   Unmarried 2,046 193 1.38 1.14–1.67 <0.001
Stage
   I 1,511 72
   II 3,502 286 0.85 0.52–1.39 0.51
   IIIA 559 69 0.91 0.43–1.92 0.80
T stage
   T1 2,223 99
   T2 2,314 207 2.23 1.48–3.37 <0.001
   T3 1,035 121 3.28 1.92–5.60 <0.001
N stage
   N0 2,643 191
   N1 2,929 236 1.31 1.00–1.70 0.048

CI, confidence interval; CSS, cancer-specific survival; ER, estrogen receptor; HR, hazard ratio; N, node; PR, progesterone receptor; T, tumor.

For OS, multivariate analysis revealed that older age (≥45 years: hazard ratio =1.33; 95% CI: 1.09–1.61), higher tumor grade (III/IV: hazard ratio =1.71; 95% CI: 1.43–2.05), unmarried status (hazard ratio =1.62; 95% CI: 1.40–1.88), advanced T stage (T2: hazard ratio =1.72, 95% CI: 1.29–2.29; T3: hazard ratio =1.90, 95% CI: 1.34–2.68) were independent risk factors. Conversely, ER positivity (hazard ratio =0.72; 95% CI: 0.57–0.92), PR positivity (hazard ratio =0.67; 95% CI: 0.54–0.83), single primary tumor (hazard ratio =0.56; 95% CI: 0.47–0.66) and receipt of chemotherapy (hazard ratio =0.59; 95% CI: 0.49–0.70) were significantly associated with improved OS.

For CSS, independent risk factors included higher tumor grade (III/IV: hazard ratio =1.70; 95% CI: 1.35–2.14), unmarried status (hazard ratio =1.38; 95% CI: 1.14–1.67), advanced T stage (T2: hazard ratio =2.23; 95% CI: 1.48–3.37; T3: hazard ratio =3.28; 95% CI: 1.92–5.60) and N1 stage (hazard ratio =1.31; 95% CI: 1.00–1.70). Protective factors were ER positivity (hazard ratio =0.70; 95% CI: 0.52–0.94), PR positivity (hazard ratio =0.55; 95% CI: 0.42–0.71) and single primary tumor (hazard ratio =0.57; 95% CI: 0.46–0.71).

Nomogram construction

Based on the multivariate Cox analysis of the training cohort, we constructed nomograms to predict OS and CSS (Figures 1,2). Each independent prognostic factor was assigned a weighted score (range, 0–100) proportional to its contribution to the outcome. The total point score for an individual, obtained by summation of all factor scores, was then converted into estimated probabilities for 1-, 3-, and 5-year OS and CSS. A higher total score consistently indicated a poorer prognosis.

Figure 1 Nomogram for OS prediction in the patients. ER, estrogen receptor; OS, overall survival; PR, progesterone receptor; T, tumor.
Figure 2 Nomogram for CSS prediction in the patients. CSS, cancer-specific survival; ER, estrogen receptor; N, node; PR, progesterone receptor; T, tumor.

Model validation

In the training cohort, the OS nomogram demonstrated a significantly higher C-index than the AJCC 7th staging system [0.69 (95% CI: 0.67–0.71) vs. 0.63 (95% CI: 0.61–0.65)]. Time‑dependent ROC analysis yielded AUCs of 0.684 (1-year), 0.701 (3-year), and 0.697 (5-year) (Figure 3A). Similarly, for CSS, the nomogram achieved a C-index of 0.74 (95% CI: 0.72–0.76) in the training cohort, with corresponding 1-, 3-, and 5-year AUCs of 0.797, 0.780, and 0.748 (Figure 3B).

Figure 3 ROC curves of the nomogram for 1-, 3-, and 5-year OS (A) and CSS (B) in training set. AUC, area under the curve; CSS, cancer-specific survival; OS, overall survival; ROC, receiver operating characteristic.

Validation results confirmed the robustness of both models. For OS, the validation cohort showed a Cindex of 0.67 (95% CI: 0.64–0.71) and 1-/3-/5-year AUCs of 0.672, 0.718, and 0.687 (Figure S2A). For CSS, the validation C-index was 0.77 (95% CI: 0.73–0.80) with AUCs of 0.813, 0.832, and 0.778 (Figure S2B).

Calibration plots indicated excellent agreement between predicted and observed outcomes for OS in both the training (Figure 4A-4C) and validation sets (Figure 4D-4F). High concordance was also observed for CSS in the training (Figure S3A-S3C) and validation cohorts (Figure S3D-S3F).

Figure 4 Calibration plots for 1-, 3-, and 5-year OS. (A) Training set, 1-year OS. (B) Training set, 3-year OS. (C) Training set, 5-year OS. (D) Validation set, 1-year OS. (E) Validation set, 3-year OS. (F) Validation set, 5-year OS. OS, overall survival.

DCA revealed favourable clinical utility of the OS nomogram in the training (Figure 5A-5C) and validation cohorts (Figure 5D-5F). Similarly, the CSS nomogram showed valuable clinical net benefit in both the training (Figure S4A-S4C) and validation sets (Figure S4D-S4F).

Figure 5 Decision curve analysis of nomogram for the 1-, 3-, and 5-year OS prediction in training cohort (A-C) and validation cohort (D-F). None: none of the patients have a bad outcome. All: bad outcomes occur in all patients. OS, overall survival.

Therapeutic efficacy across risk-stratified subgroups

Drawing upon X-tile-derived optimal cut-off values, patients were stratified into three distinct prognostic tiers: low-risk (total score: OS <129, CSS <104), intermediate-risk (OS: 129–247, CSS: 104–205), and high-risk (OS ≥248, CSS ≥206) (Figure S5). Kaplan-Meier survival curves demonstrated statistically significant stratification across these groups for both OS and CSS (Figure 6), with superior outcomes observed in the low-risk cohort and progressively poorer survival associated with higher risk scores.

Figure 6 Kaplan-Meier OS (A) and CSS (B) curves with different risk group stratified by the nomogram. CSS, cancer-specific survival; OS, overall survival.

Subgroup analyses, performed after PSM, evaluated the differential impact of systemic therapies. In both the low- and intermediate-risk strata, neither adjuvant chemotherapy nor NAC conferred a significant survival advantage for OS or CSS (Figure 7 and Figure S6). However, among patients receiving NAC in the low- and medium-risk groups, those achieving CR demonstrated a significantly better prognosis than those with NCR (Figure 8). What is more, we found that both adjuvant chemotherapy and NAC demonstrated improved OS and CSS in high-risk group patients (Figure 9). Interestingly, patients achieving a CR after NAC had superior survival outcomes compared to those receiving postoperative chemotherapy, while patients with NCR to NAC showed inferior survival outcomes compared to postoperative chemotherapy patients (Figure 9). It was revealed that within the high-risk group, patients achieving a CR to NAC had a significantly better prognosis than those with an NCR (Figure S7).

Figure 7 Comparison of Kaplan-Meier survival curves between patients who did and did not receive adjuvant chemotherapy in different risk groups. (A) OS in the low-risk group. (B) CSS in the low-risk group. (C) OS in the middle-risk group. (D) CSS in the middle-risk group. CSS, cancer-specific survival; OS, overall survival.
Figure 8 Comparison of survival outcomes between patients achieving a CR and those with an NCR following neoadjuvant chemotherapy, stratified by risk group. (A) OS in the low-risk group. (B) CSS in the low-risk group. (C) OS in the intermediate-risk group. (D) CSS in the intermediate-risk group. CR, complete response; CSS, cancer-specific survival; NCR, non-complete response; OS, overall survival.
Figure 9 Kaplan-Meier analysis for different chemotherapy strategies in high-risk patients group. Adjuvant vs. no chemotherapy in high-risk patients: OS (A) and CSS (E). Neoadjuvant vs. no chemotherapy in high-risk patients: OS (B) and CSS (F). The comparison between patients who received adjuvant chemotherapy and those who receive neoadjuvant chemotherapy in the high-risk patients group of CR for OS (C) and CSS (G). The comparison between patients who received adjuvant chemotherapy and those who receive neoadjuvant chemotherapy in the high-risk patients group of NCR for OS (D) and CSS (H). CR, complete response; CSS, cancer-specific survival; NCR, non-complete response; OS, overall survival.

Discussion

BC remains a leading cause of cancer-related mortality in women worldwide, with HER2-negative subtypes constituting over 70% of early-stage cases (15). BCS combined with radiotherapy is the cornerstone of treatment for T1–3N0–1 disease, offering excellent locoregional control while preserving quality of life (16). However, significant heterogeneity exists within this population, where patients with adverse features—including larger tumor size (T2–3), high histological grade, limited nodal involvement (N1), or hormone receptor negativity—experience up to a 3-fold increase in recurrence risk compared to their low-risk counterparts (17). Critically, the benefit of systemic chemotherapy, particularly when administered NAC, varies substantially across this spectrum. Pathological CR to NAC is a well-established surrogate for long-term survival in aggressive subtypes like TNBC, yet fewer than 40% of HER2-negative patients achieve this milestone (18). Conversely, residual disease signifies persistent micrometastatic burden and necessitates intensified adjuvant strategies (19). Despite these insights, the inability to reliably predict chemotherapy response or identify patients most likely to benefit from NAC hampers personalized decision-making (20,21). Our study addresses this unmet need by developing and validating the first nomograms integrating baseline clinicopathological factors and treatment response to predict long-term survival in HER2-negative T1–3N0–1 BC patients treated with BCS.

Through rigorous analysis of 8,384 patients from the SEER registry, we identified tumor grade, T stage, ER/PR status, marital status, and tumor sequence as independent predictors of OS and CSS. Advanced T stage (T2: OS hazard ratio =1.72, CSS hazard ratio =2.23; T3: OS hazard ratio =1.90, CSS hazard ratio =3.28) and high-grade histology (grade III/IV: OS hazard ratio =1.71, CSS hazard ratio =1.70) emerged as dominant risk factors, aligning with established literature on their association with aggressive tumor biology and metastatic potential (22). The protective role of hormone receptor positivity (ER+: OS hazard ratio =0.72; PR+: OS hazard ratio =0.67) underscores the therapeutic advantage of endocrine therapies in this population—a finding consistent across previous studies (23,24). Notably, unmarried status independently predicted poorer survival (OS hazard ratio =1.62, CSS hazard ratio =1.38), likely reflecting socioeconomic disparities in treatment access, adherence, or social support systems rather than biological mechanisms. Most innovatively, our study established “single primary tumor” as a novel favorable prognostic factor (OS hazard ratio =0.56; CSS hazard ratio =0.57). This finding challenges conventional staging paradigms and suggests that multiple primaries may indicate field cancerization, genetic predisposition, or compromised immune surveillance—mechanisms warranting further molecular investigation. These variables were integrated into visually accessible nomograms that outperform the AJCC 7th staging system, providing clinicians with a dynamic tool for risk quantification beyond static anatomical staging.

A pivotal contribution of this work lies in its risk-adapted evaluation of chemotherapy efficacy. Using X-tile-derived thresholds, we stratified patients into low-, middle-, and high-risk groups. Crucially, adjuvant chemotherapy provided no significant OS or CSS benefit in low-risk patients, while in middle-risk groups, its impact was marginal. This aligns with recent de-escalation trials demonstrating that chemotherapy may be safely omitted in genomically low-risk hormone receptor-positive disease (25,26). Our findings extend this paradigm to clinicopathologically defined low-risk HER2-negative BC, suggesting that routine chemotherapy exposes these patients to unnecessary toxicity without survival gains.

Conversely, high-risk patients derived substantial benefit from chemotherapy. More importantly, we observed a differential effect based on treatment timing and response. NAC significantly improved survival only when CR was achieved. In middle-risk patients, CR after NAC yielded superior outcomes versus NCR. High-risk patients achieving CR with NAC had better OS and CSS than those receiving adjuvant chemotherapy, whereas NCR patients fared worse than their adjuvant-treated counterpart.

These results illuminate two critical principles. CR is a transformative endpoint—its achievement identifies chemosensitive tumors where NAC may be curative, particularly in high-risk disease. NCR requires alternative strategies—residual disease signals intrinsic resistance, necessitating postoperative escalation or novel agents. This paradigm shift toward response-adapted therapy underscores NAC’s dual role: tumor downstaging and “in vivo” chemosensitivity testing. Our data suggest that high-risk patients should be prioritized for NAC, with subsequent treatment intensity tailored to pathological response.

While the nomograms demonstrated a statistically significant improvement over the AJCC 7th system, their discriminative ability (C-index: 0.69 for OS, 0.74 for CSS) must be interpreted as modest. Consequently, these models are best suited for group-level risk stratification and should serve as an adjunct to, rather than a replacement for, clinical judgment in individual patient management. Calibration showed excellent concordance in predicted group and observed group. DCA confirmed net benefit across threshold probabilities. These tools address a critical gap in managing HER2-negative BC. By quantifying individualized risk, clinicians can avoid overtreatment in low-risk patients (33% of cohort), sparing toxicity. High-risk patients (27% of the cohort) should be prioritized for NAC to capitalize on the survival gains linked to achieving CR. Patients who do not achieve CR can then be redirected to adjuvant trials exploring novel agents.

Several limitations merit acknowledgment: (I) the retrospective SEER data lack granular details on chemotherapy regimens, radiation doses, endocrine therapy adherence, and molecular markers; (II) CR assessment was registry-based without central pathology review, potentially misclassifying residual disease burden; and (III) using “unmarried” status as a risk factor may mask the interplay of biological, social, and healthcare-access variables. External validation in prospective cohorts is essential. It is important to acknowledge that while our nomogram demonstrated a statistically significant improvement over the AJCC 7th system, the absolute gain in discriminative ability (C-index) is modest. This inherently limits its precision for predicting outcomes for individual patients. Therefore, the primary clinical value of this model lies not in providing definitive predictions, but in serving as a decision aid for risk stratification at the group level, as supported by the net benefit shown in DCA. Future efforts should therefore focus on integrating genomic signatures with clinicopathological nomograms to refine risk prediction, exploring biomarkers of NAC response for early identification of non-responders, and designing trials that randomize high-risk patients to NAC versus adjuvant chemotherapy with response-adaptive crossover.


Conclusions

In HER2-negative early-stage BC treated with BCS, our study delivers three key advances: first, we have developed validated nomograms integrating tumor biology, treatment response, and social factors that predict long-term survival more accurately than conventional staging. Second, a risk-adapted strategy, in which chemotherapy avoidance may be considered for low-risk groups, NAC could be prioritized for high-risk patients, and alternative strategies might be explored for NAC non-responders. Third, we identified “single primary tumor” status as a novel prognostic indicator, suggesting unexplored biological mechanisms in tumorigenesis. These tools empower clinicians to navigate HER2-negative BC heterogeneity—optimizing survival while minimizing unnecessary toxicity. Prospective validation and biomarker integration will further advance precision medicine for this population.

However, these findings and their implications must be interpreted in the context of the study’s limitations, including its retrospective nature and the need for external validation in independent, prospective cohorts. If validated, these tools could eventually help clinicians navigate the heterogeneity of HER2-negative BC—with the goal of optimizing survival while minimizing unnecessary toxicity. Therefore, prospective validation and the integration of novel biomarkers are essential next steps to confirm the clinical utility of our model and advance precision medicine for this population.


Acknowledgments

We would like to thank all the researchers for the SEER program.


Footnote

Reporting Checklist: The authors have completed the TRIPOD reporting checklist. Available at https://gs.amegroups.com/article/view/10.21037/gs-2025-301/rc

Peer Review File: Available at https://gs.amegroups.com/article/view/10.21037/gs-2025-301/prf

Funding: This study was supported by the National Natural Science Foundation of China (Nos. 82372078 and 82203688).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-301/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.


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Cite this article as: Zhu S, Lu W, Zhang K, Yang H, Yang C, Guo C, Guo L, Xue X, Wang Z, Xuan L. Development and validation of a survival-predicting nomogram for HER2-negative T1–3N0–1 breast cancer treated with breast-conserving surgery: a Surveillance, Epidemiology, and End Results (SEER) database analysis. Gland Surg 2026;15(2):40. doi: 10.21037/gs-2025-301

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