Abstract
Background
Neoadjuvant therapy (NAT) is widely used in the treatment of breast cancer, and the pathological complete response (pCR) rate is increasing. However, currently, the prediction of pCR still lacks accuracy. This study aimed to investigate the accuracy of minimally invasive biopsy techniques in predicting breast pCR (bpCR) after NAT in breast cancer.
Methods
From October 2022 to October 2024, a prospective single-arm study was conducted on 132 patients with primary breast cancer who achieved breast radiologic complete response (brCR) or breast radiologic partial response (brPR) after NAT at the Breast Center of Shandong Cancer Hospital. Before NAT, a marker clip was placed at the center of the tumor bed. After NAT, in patients with no residual lesions suggested by ultrasound, iodine-125 was placed under the guidance of mammography, followed by routine breast surgery (breast-conserving surgery or mastectomy). Postoperatively, multiple-site core needle biopsy (CNB) under ultrasound guidance was performed on the surgical specimen. The pathological results of CNB specimens were compared with those of surgical specimens to assess the accuracy of CNB in predicting bpCR (ypT0) after NAT.
Results
A total of 52 patients (39.4%) achieved bpCR after NAT. Univariate analysis showed that tumor molecular subtypes, brCR after NAT, and axillary pathological complete response (apCR) were significantly associated with bpCR (P=0.02, 0.02, and P<0.001, respectively). Ultrasound-guided multiple-site CNB had an accuracy, negative predictive value (NPV), and false-negative rate (FNR) of 90.9%, 81.0%, and 14.8%, respectively, in predicting bpCR after NAT, which were superior to those of ultrasound, mammography, and magnetic resonance imaging. The combination of imaging examinations and ultrasound-guided multiple-site CNB significantly reduced the FNR compared with CNB alone (7.4% vs. 14.8%; P<0.001). No false-negative results were found in 45 cases using large-bore CNB needles (12G).
Conclusions
The combination of imaging examinations and ultrasound-guided multiple-site CNB has the potential to accurately predict bpCR after NAT, making it possible to selectively avoid breast surgery in breast cancer patients after NAT.
Keywords: Breast cancer, neoadjuvant therapy (NAT), breast pathological complete response (bpCR), core needle biopsy (CNB)
Highlight box.
Key findings
• The key finding of this study is that the combination of imaging examinations and ultrasound-guided multiple-site core needle biopsy (CNB) can accurately predict pathological complete response (bpCR) after neoadjuvant therapy (NAT).
What is known and what is new?
• The known content is that ultrasound-guided multiple-site CNB has the potential to predict bpCR after NAT.
• This manuscript adds the combination of imaging examinations and ultrasound-guided multiple-site CNB.
What is the implication, and what should change now?
• The finding provides assistance for selectively exempting mastectomy after NAT in the future.
Introduction
Neoadjuvant therapy (NAT) refers to systemic cytotoxic drug treatment administered before surgery for non-metastatic tumors, also known as preoperative chemotherapy or induction chemotherapy. It has been widely recognized and applied. NAT not only makes inoperable breast cancer operable but also enables patients who wish to preserve their breasts to undergo breast-conserving surgery. Additionally, it serves as an in vivo drug sensitivity test (1).
Recent years have witnessed significant advancements in the systemic treatment of breast cancer. Some studies have highlighted the importance of personalized treatment strategies and the role of targeted therapies in improving patient outcomes (2,3). With the continuous improvement of NAT guided by molecular subtypes and the efficacy of targeted therapies, the pathological complete response (pCR) rate has been increasing, especially in triple-negative breast cancers (TNBC) and human epidermal growth factor receptor 2 positive (HER2+) breast cancers, where the pCR rate can reach 60% or higher. pCR after NAT not only serves as a surrogate marker for long-term survival in breast cancer patients (4) but also influences the de-escalation of local-regional treatment in breast cancer (5-7). Currently, patients who achieve breast pCR (bpCR) after NAT still undergo standard breast surgery without considering the significant pathological response. Given the high bpCR rates in some subgroups after NAT, especially in patients undergoing breast-conserving surgery and receiving adjuvant whole-breast radiotherapy, it is necessary to question whether surgery is a redundant component in the comprehensive management of this subset of breast cancer (8). The key to potentially avoiding breast surgery lies in the accurate preoperative assessment of bpCR. This study aims to explore the accuracy of ultrasound-guided multiple-site core needle biopsy (CNB) in predicting bpCR after NAT, providing a reliable minimally invasive diagnostic basis for selectively avoiding breast surgery after NAT. We present this article in accordance with the STROBE reporting checklist (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-103/rc).
Methods
Patient data and inclusion criteria
This study is a prospective single-arm enrollment study and has been registered on the NIH ClinicalTrials.gov (NCT03789851). A total of 132 patients with primary breast cancer who achieved breast radiologic complete response (brCR) or breast radiologic partial response (brPR) after NAT were enrolled from October 2022 to October 2024 at the Breast Center of Shandong Cancer Hospital. Inclusion criteria: all patients were female with unilateral, solitary T1–3N0–3M0 breast cancer; a marker clip was placed at the center of the tumor bed before NAT; brCR or brPR confirmed by ultrasound, mammography, and magnetic resonance imaging (MRI) after NAT [evaluated according to response evaluation criteria in solid tumors 1.1 (9) criteria, with brPR requiring a tumor diameter ≤3 cm after NAT], and all three imaging examinations suggested centripetal shrinkage of the mass; any subtype; residual target lesions or marker clips were clearly visible on ultrasound or mammography. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by Shandong Cancer Hospital Affiliated to Shandong First Medical University Ethics Committee (No. SDTHEC2023003005) and informed consent was taken from all the patients.
Treatment
The preoperative NAT regimens for enrolled patients were determined by the attending physician according to the latest guidelines from the National Comprehensive Cancer Network or the St. Gallen consensus. HER2+ breast cancer patients received a treatment regimen based on trastuzumab and pertuzumab, while TNBC patients received neoadjuvant chemotherapy combined with immunotherapy. After NAT, all patients underwent routine breast surgery (breast-conserving surgery or mastectomy). Patients who underwent sentinel lymph node biopsy after NAT all used a combined tracing technique, with preoperative injection of a radioactive tracer and intraoperative use of methylene blue dye to locate sentinel lymph nodes.
Assessment of tumor response after NAT
All patients underwent comprehensive imaging assessments after surgery. brCR was defined as no residual lesions detected in the breast by imaging examinations (ultrasound, mammography, and MRI) after NAT (excluding the marker clip). Biopsy tissues, surgical specimens, and axillary lymph nodes were assessed by specialized breast pathologists: bpCR was defined as no invasive cancer in the breast primary tumor (i.e., ypT0), and axillary lymph nodes with macro-metastasis, micro-metastasis, or isolated tumor cells were defined as positive.
Use of iodine-125
Since ultrasound cannot accurately locate the marker clip, patients with no residual lesions suggested by ultrasound after NAT can have iodine-125 placed at the marker clip position under the guidance of mammography before surgery. The postoperative specimen is then located using a gamma probe to guide the ultrasound-guided multiple-site CNB (Figure 1).
Figure 1.
Ultrasound, mammography and MRI images of a patient before and after NAT. (A,B,E,G) The original tumor areas on the pre-NAT mammographic craniocaudal view, mediolateral oblique view, MRI, and ultrasound (indicated by white arrows), respectively. (C,D,F,H) The original tumor areas on the post-NAT mammographic craniocaudal view, mediolateral oblique view, MRI, and ultrasound (the tumor has completely disappeared after NAT, indicated by white arrows). (C,D) The placement of iodine-125 (indicated by red arrows) at the position of the marker clip (indicated by blue arrows) under mammographic guidance. MRI, magnetic resonance imaging; NAT, neoadjuvant therapy.
Ultrasound-guided CNB
A 0.5-cm radius around the marker clip was defined as the first area, another 0.5-cm radius as the second area, and another 0.5-cm radius as the third area. Four biopsy specimens were evenly taken from each area (Figure 2), and the biopsied specimens were subjected to routine pathological examination. The biopsy range was determined based on the tumor size after NAT; if brCR was achieved after NAT, the first area was biopsied around the marker clip. Two types of CNB needles were used in this study: (I) standard CNB needle (14G); (II) large-bore CNB needle (12G).
Figure 2.
Ultrasound-guided core needle biopsy model.
Statistical analysis
Statistical analyses were performed using SPSS 26.0 software. For normally distributed continuous data, comparisons were made using the t-test; for non-normally distributed continuous data, the Mann-Whitney U test was used. For categorical data, comparisons between groups were made using the chi-squared test or Fisher’s exact test. The significance level was set at α=0.05.
Results
Clinical and pathological characteristics of patients
The median age of the 132 patients was 48.5 years (range, 28–66 years), and the median initial tumor size was 3.3 cm (range, 1.2–8.4 cm). Among them, 47 patients (35.6%) underwent breast-conserving surgery, 20 patients (15.2%) underwent breast reconstruction, and 65 patients (49.2%) underwent mastectomy. A total of 105 patients (79.5%) had clinical T1/2 disease, and 102 patients (77.3%) had axillary lymph node metastasis confirmed by fine-needle aspiration cytology. The distribution of molecular subtypes was as follows: hormone receptor (HR)+/HER2− in 36 patients (27.3%), HER2+ in 51 patients (38.6%), and TNBC in 45 patients (34.1%).
Analysis of clinical and pathological factors associated with bpCR after NAT
A total of 52 patients (39.4%) achieved bpCR after NAT, including 6 HR+/HER2− patients, 27 HER2+ patients, and 19 TNBC patients. Univariate analysis showed that menopausal status, histology, surgical approach, clinical T and N stages were not significantly associated with bpCR after NAT (all P>0.05). In contrast, tumor molecular subtype, brCR after NAT, and axillary pathological complete response (apCR) were significantly associated with bpCR (P=0.02, P=0.02, and P<0.001, respectively) (see Table 1). The bpCR rates after NAT were 52.9% (27/51) for HER2+ patients and 42.2% (19/45) for TNBC patients, which were significantly higher than that for HR+/HER2− patients (6/36, 16.7%) (P=0.01 and P=0.03, respectively). Among the 27 patients who achieved brCR after NAT, 66.7% (18/27) achieved bpCR; whereas among the 105 patients who achieved brPR after NAT, 32.4% (34/105) achieved bpCR. Among the 52 patients who achieved bpCR after NAT, 92.3% (48/52) achieved apCR.
Table 1. The correlation between bpCR after NAT and clinicopathological characteristics.
| Characteristics | All patients (n=132) | bpCR (n=51) | Percentage, % | P |
|---|---|---|---|---|
| Menopausal status | 0.19 | |||
| Menopause | 84 | 27 | 32.1 | |
| No menopause | 48 | 24 | 50.0 | |
| Pathological types | 0.96 | |||
| Invasive ductal carcinoma | 108 | 42 | 38.9 | |
| Invasive lobular carcinoma | 9 | 3 | 33.3 | |
| Other | 15 | 6 | 40.0 | |
| Molecular subtypes | 0.03 | |||
| HR+/HER2− | 51 | 9 | 17.6 | |
| HER2+ | 45 | 24 | 53.3 | |
| TNBC | 36 | 18 | 50.0 | |
| Clinical tumor staging | 0.34 | |||
| T1 | 15 | 6 | 40.0 | |
| T2 | 90 | 35 | 38.9 | |
| T3 | 27 | 10 | 37.0 | |
| Clinical lymph node staging | 0.19 | |||
| N0 | 21 | 10 | 47.6 | |
| N1 | 66 | 26 | 39.4 | |
| N2 | 24 | 9 | 37.5 | |
| N3 | 21 | 6 | 28.6 | |
| Radiologic response of the primary tumor | 0.02 | |||
| brCR | 27 | 18 | 66.7 | |
| brPR | 105 | 33 | 31.4 | |
| Pathologic response of the lymph nodes | <0.001 | |||
| apCR | 75 | 48 | 64.0 | |
| Non-apCR | 57 | 3 | 5.3 | |
| Surgical approach | 0.20 | |||
| Breast-conserving surgery | 21 | 12 | 57.1 | |
| Mastectomy | 111 | 39 | 35.1 | |
apCR, axillary pathologic complete response; bpCR, breast pathologic complete response; brCR, breast radiologic complete response; brPR, breast radiologic partial response; HER2+, human epidermal growth factor receptor 2 positive; HR, hormone receptor; N, node; NAT, neoadjuvant therapy; T, tumor; TNBC, triple-negative breast cancer.
Accuracy of ultrasound-guided CNB in predicting bpCR after NAT
The median number of tissue cores obtained by ultrasound-guided multiple-site CNB was 8 (range, 4–12). The accuracy, negative predictive value (NPV), and false-negative rate (FNR) of ultrasound-guided multiple-site CNB in predicting bpCR after NAT were 90.9%, 81.0%, and 14.8%, respectively, which were superior to those of ultrasound, mammography, and MRI (see Table 2). Among the 63 patients with bpCR confirmed by multiple-site CNB, 51 were confirmed to have bpCR by routine pathology, 6 had ductal carcinoma in situ, and 6 had invasive cancer with a diameter <5 mm. One patient confirmed to have non-bpCR by multiple-site CNB was found to have no residual disease by routine pathology, indicating that the residual cancer foci after NAT were completely removed by multiple-site CNB in this patient. Among the 12 false-negative patients, there were 6 HR+/HER2− patients, 3 HER2+ patients, and 3 TNBC patients. The FNR of ultrasound-guided multiple-site CNB in predicting bpCR after NAT was 14.3% for HR+/HER2−, 14.3% for HER2+, and 16.6% for TNBC (P>0.05). The combination of imaging examinations and ultrasound-guided multiple-site CNB significantly reduced the FNR compared with CNB alone (7.4% vs. 14.8%; P<0.001). No false-negative results were found in 45 patients who used large-bore CNB needles (12G) (FNR 0%, NPV 100%).
Table 2. The accuracy of ultrasound, mammography, MRI, and ultrasound-guided multi-point CNB to predict bpCR after NAT.
| Variable | Predictable method | ||||
|---|---|---|---|---|---|
| Ultrasound | Mammography | MRI | Ultrasound-guided multi-point CNB | Ultrasound-guided CNB combined imaging examination | |
| Accuracy, % | 65.9 | 75.0 | 79.5 | 90.9 | 70.5 |
| Sensitivity, % | 74.1 | 85.2 | 77.8 | 85.2 | 92.6 |
| Specificity, % | 52.9 | 58.8 | 82.4 | 100.0 | 35.3 |
| FNR, % | 25.9 | 14.8 | 22.2 | 14.8 | 7.4 |
| PPV, % | 71.4 | 76.7 | 87.5 | 100.0 | 69.4 |
| NPV, % | 56.2 | 71.4 | 70.0 | 81.0 | 75.0 |
bpCR, breast pathologic complete response; CNB, core needle biopsy; FNR, false negative rate; MRI, magnetic resonance imaging; NAT, neoadjuvant therapy; NPV, negative predictive value; PPV, positive predictive value.
Discussion
NAT has been widely applied in the treatment of breast cancer, with the ideal outcome being the achievement of bpCR. To date, tumor molecular subtypes, NAT regimens, and breast imaging examinations have all lacked accuracy in predicting bpCR after NAT. Therefore, conventional breast surgery after NAT has been considered necessary and the only effective method for both completely removing residual lesions in patients with non-bpCR after NAT and diagnosing bpCR (10,11). With the continuous improvement of NAT guided by molecular subtypes and the efficacy of targeted therapies, the rate of bpCR has significantly increased. NAT has significantly promoted the de-escalation of local-regional treatment in breast cancer (5-7). However, the necessity of performing breast surgery in patients who achieve bpCR after NAT has been questioned, especially in patients undergoing breast-conserving surgery and receiving adjuvant whole-breast radiotherapy (8). The concept of selectively avoiding breast surgery in patients with bpCR after NAT is not new. Early exploratory studies (12,13) used brCR after NAT as an enrollment criterion to evaluate the efficacy of radiotherapy as an alternative to breast surgery, but the results led to a higher rate of local-regional recurrence. This was because brCR was not pathologically confirmed as bpCR, and the residual tumor burden, which may have been substantial, could not be effectively controlled by radiotherapy and subsequent systemic therapy alone. The main obstacle to potentially avoiding breast surgery is that conventional and functional breast imaging techniques cannot accurately predict residual disease. However, minimally invasive biopsy (MIB) techniques guided by imaging methods hold promise to overcome this obstacle (14).
Heil et al. (15) first reported the use of MIB techniques to predict bpCR after NAT. In 164 breast cancer patients who achieved brCR after NAT, preoperative CNB or vacuum-assisted biopsy (VAB) guided by ultrasound or mammography was performed. The NPV and FNR of MIB in predicting bpCR after NAT were 71.3% and 49.3%, respectively. However, no false-negative results were found with mammography-guided VAB (NPV 100%, FNR 0%). The overall high FNR in this trial was due to factors such as insufficient sampling of the tumor bed tissue and the lack of clear imaging criteria (15,16). Heil et al. (17) further demonstrated the potential of VAB to predict bpCR in another study involving 50 breast cancer patients with brCR or brPR after NAT. Preoperative ultrasound-guided VAB predicted bpCR after NAT with an NPV of 76.7% and an FNR of 25.9%. In VAB samples with histological representativeness, the NPV and FNR were 94.4% and 4.8%, respectively. However, the histological representativeness of VAB samples in Heil’s study was determined subjectively by the clinical and radiological physicians performing the VAB, without corresponding evaluation criteria. In contrast, our study placed iodine-125 to locate the tumor bed before surgery in patients who achieved brCR after NAT, which guided the ultrasound-guided multiple-site CNB to reduce sampling error. The resulting NPV and FNR were 90.0% and 5.3%, respectively, similar to the results reported by Kuerer et al. from the MD Anderson Cancer Center (18).
If breast cancer patients with bpCR confirmed by imaging-guided MIB after NAT can avoid breast surgery, how should the axilla be managed? A retrospective analysis by the MD Anderson Cancer Center of 527 patients with cT1–2N0–1M0 HER2-positive and triple-negative breast cancer found that among the initial ultrasound cN0 group of 290 patients, none of the 116 patients with bpCR after NAT had residual axillary lymph node metastasis. In the initial biopsy-confirmed cN1 group of 237 patients, 89.6% of the 77 patients with bpCR after NAT achieved apCR (19). Our study also showed that among the 52 patients with bpCR after NAT, 92.3% (48/52) achieved apCR, indicating a high concordance between bpCR and apCR. This provides a theoretical basis for selectively avoiding axillary surgery in patients with bpCR after NAT (20,21).
Our study holds significant potential in advancing the field of breast cancer treatment by providing a reliable minimally invasive diagnostic basis for selectively avoiding breast surgery after NAT. The knowledge gaps in accurately predicting bpCR after NAT are primarily related to the limitations of current imaging techniques and biopsy methods. Our study addresses these gaps by demonstrating the superior accuracy of ultrasound-guided multiple-site CNB compared to traditional imaging methods. Looking ahead, we envision that the integration of advanced imaging technologies and more precise biopsy techniques will further enhance the accuracy of bpCR prediction. Over the next 5 years, we anticipate that personalized treatment strategies will become more prevalent, and the role of minimally invasive diagnostic methods will become increasingly important in guiding treatment decisions.
Conclusions
In summary, bpCR after NAT is not associated with patient age, menopausal status, histology, surgical approach, or clinical tumor and lymph node staging (all P>0.05), but is significantly associated with tumor molecular subtype, brCR after NAT, and apCR (P=0.01, P=0.04, and P=0.001, respectively). Ultrasound-guided multiple-site CNB has higher accuracy, NPV, and lower FNR in predicting bpCR after NAT compared to ultrasound, mammography, MRI, and the combination of the three. The combination of imaging examinations and ultrasound-guided multiple-site CNB did not improve the NPV compared to CNB alone in predicting bpCR after NAT, but significantly reduced the FNR (7.4% vs. 14.8%; P<0.001). Ultrasound-guided multiple-site CNB has the potential to accurately predict bpCR after NAT, providing a theoretical basis for selectively avoiding breast surgery after NAT. This could help reduce postoperative complications, improve patients’ quality of life, and lower medical costs. However, the optimal biopsy range for ultrasound-guided multiple-site CNB and the local-regional recurrence and long-term efficacy of selectively avoiding breast surgery after NAT still require further research.
Limitation
Despite the promising results of our study, there are several limitations that should be acknowledged. First, our study is a single-center study with a relatively small sample size, which may limit the generalizability of our findings. Second, the accuracy of ultrasound-guided multiple-site CNB may be influenced by the experience of the operators and the quality of imaging equipment. Future multicenter studies with larger sample sizes and standardized protocols are needed to further validate our findings and address these limitations.
Supplementary
The article’s supplementary files as
Acknowledgments
None.
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. The study was approved by Shandong Cancer Hospital Affiliated to Shandong First Medical University Ethics Committee (No. SDTHEC2023003005) and informed consent was taken from all the patients.
Footnotes
Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://gs.amegroups.com/article/view/10.21037/gs-2025-103/rc
Funding: This work was supported by grants from the National Natural Science Foundation of China (Nos. 81672638 and W2421095), National Natural Science Foundation of Shandong Province (No. ZR2024LMB011), and Collaborative Academic Innovation Project of Shandong Cancer Hospital (No. GF003).
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://gs.amegroups.com/article/view/10.21037/gs-2025-103/coif). The authors have no conflicts of interest to declare.
Data Sharing Statement
Available at https://gs.amegroups.com/article/view/10.21037/gs-2025-103/dss
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