Ability of MRI Breast to Predict Pathologic Complete Response Following Neoadjuvant Systemic Therapy in Patients with Breast Cancer

Abstract

Neoadjuvant systemic therapy (NST) has revolutionized the management of breast cancer by downstaging the disease and improving survival rates. Pathologic complete response, where surgical histopathological examination shows no invasive cancer in the breast and axilla, is not an uncommon scenario. In such patients, surgery may have added value to cancer control only for documenting the absence of cancer cells in the body in response to NST. In other words, could we have forfeited surgery for such patients if we were able to reliably identify them before surgery? However, the challenge lies in accurately identifying such patients. This narrative literature review explores the predictive ability of MRI scans in assessing pathological complete response (pCR) following NST. MRI demonstrates high sensitivity and specificity in detecting residual tumors post-NST, outperforming conventional imaging modalities. Combining diffusion-weighted MRI and contrast-enhanced MRI enhances diagnostic accuracy, particularly in monitoring response to chemotherapy. However, MRI's limitations include over- or underestimation of lesion size and morphology, necessitating complementary approaches for precise assessment. Vacuum-assisted core biopsy (VACB) emerges as a promising adjunct to MRI, offering high negative predictive value and minimal invasiveness. MRI-guided VACB enables accurate tissue sampling and lesion verification, augmenting diagnostic certainty. This integrated approach could particularly benefit patients with smaller-sized triple-negative or HER2-positive tumors. Further research is warranted to establish the clinical utility of combined MRI and VACB in predicting pCR post-NST and guiding personalized treatment decisions. Such advancements hold promise for a paradigm shift in breast cancer management, sparing patients from avoidable surgeries and optimizing therapeutic outcomes.

 

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Keywords

pathologic complete response - neoadjuvant systemic therapy - diffusion-weighted MRI - contrast-enhanced MRI - breast MRI

Introduction

Patients with breast cancer are often administered neoadjuvant systemic therapy (NST), where chemotherapy is delivered prior to surgical management, for downstaging of disease, for improving overall survival, and for reducing the risk of disease recurrence.[1] The stage of the breast cancer, including axillary nodal status, is one of the important factors in deciding whether to administer NST. It also helps in converting mastectomy to lumpectomy in patients with larger tumor sizes. NST results in a pathological complete response (pCR) rate of 50 to 60% in patients with triple negative breast cancer (TNBC) and HER2-positive breast cancers.[2] Such high response rates raise the possibility of completely avoiding breast surgery in some patients. What was previously unthinkable is now a real possibility—a paradigm shift in the management of breast cancer.

A nonrandomized study from seven centers in the United States investigated such a strategy of eliminating breast surgery for invasive breast cancer in exceptional responders to NST. Kuerer et al recruited 50 women, of 40 years or older, with either unicentric cT1–2 and N0–1 TNBC or HER2-positive breast cancer who presented with a residual breast lesion of less than 2 cm on imaging following NST.[2] Prior to the commencement of NST, percutaneous biopsies were conducted on any lymph nodes exhibiting suspicious characteristics to ascertain the presence of metastatic disease. In instances where nodal disease was confirmed, a clip was inserted into the biopsied node to aid in subsequent identification and retrieval. All patients received image-guided vacuum-assisted core biopsy (VACB) following NST. Thirty-one patients who had a pCR by VACB proceeded to whole-breast radiotherapy without breast surgery, and were assessed for efficacy and safety. After a follow-up of 26 months, none of these 31 patients who omitted surgery developed recurrence.[2]

The remarkable findings, albeit a small nonrandomized study, bring up an exciting possibility of sparing some women with breast cancer from undergoing mastectomy or lumpectomy. Here, the key question is how to select such patients who can benefit from such therapeutic strategy without a heightened risk for local or distant recurrence. Can an MRI scan of the breast, done after completion of NST, help in predicting pCR (with or without biopsies), and therefore help us select patients who can proceed to a nonsurgical management of breast cancer? In this article, we aimed to review clinical studies that have investigated the predictive ability of MRI of the breast for pCR. We aimed to identify factors related to imaging findings as well as tumor characteristics that have greater predictive ability for pCR.

 

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Materials and Methods

We conducted a narrative literature review to identify clinical studies on patients with breast cancer where an MRI scan was done during or after NST and prior to surgery. All the studies must report factors related to MRI scans, tumor characteristics, and pCR rates.

 

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Results

We identified 10 studies ([Table 1]), among which 2 were meta-analyses. The other studies used various designs, including prospective cohorts, trials, and retrospective cohorts.

Table 1 Summary of clinical studies

No.	Study details (author)	Study population	Methodology	Results	Conclusions
1.	American College of Radiology Imaging Network 6657 Trial Scheel et al[3]	138 women with ≥ 3 cm invasive breast cancer receiving NACT	Preoperative measurements of residual disease included the longest diameter by mammography, MRI, and clinical examination, and functional volume on MRI. The accuracy of preoperative measurements for detecting pCR was assessed	The longest diameter by MRI showed the highest accuracy for detecting pathologic CR for all lesions and NME	Measurement of the longest diameter by MRI is more accurate than by mammography and clinical examination for preoperative assessment of tumor residua after NACT and may improve surgical planning
2.	Meta-analysis of magnetic resonance imaging in detecting residual breast cancer after neoadjuvant therapy Marinovich et al[19]	44 studies with a total of 2,050 patients were included	Patients enrolled in included studies had predominantly stage II and III cancers, and the majority had invasive ductal carcinoma. NAC was primarily anthracycline-taxane-based, either sequential or in combination. Trastuzumab was used in 11 studies. Radiotherapy was given before surgery in two studies	Specificity was higher when negative MRI was defined as contrast enhancement less than or equal to normal tissue vs. no enhancement, with comparable sensitivity	MRI accurately detects residual tumors after neoadjuvant chemotherapy. Accuracy was lower when pCR was more rigorously defined, and specificity was lower when test negativity thresholds were more stringent. MRI is more accurate than mammography
3.	Can diffusion-weighted MR imaging and contrast-enhanced MR imaging precisely evaluate and predict pathological responses to neoadjuvant chemotherapy in patients with breast cancer? Wu et al[5]	34 studies with 1,932 pathologically confirmed patients (34 of the studies included 6 of DW-MRI and 30 of CE-MRI)	Meta-analysis of all available studies of the diagnostic performance of DW-MRI or CE-MRI to evaluate and predict pathological response to NAC in patients with breast cancer	DW-MRI sensitivity: 0.93, specificity: 0.82 CE-MRI sensitivity: 0.68, specificity: 0.91	DW-MRI is highly sensitive, while CE-MRI is highly specific in predicting pathological responses to NAC in breast cancer patients. The combined use of DW-MRI and CE-MRI has the potential to improve diagnostic performance in monitoring NAC
4.	Comparison of mammography, sonography, MRI, and clinical examination in patients with locally advanced or inflammatory breast cancer who underwent neoadjuvant chemotherapy. Shin et al[4]	43 patients with locally advanced or inflammatory breast cancer (age range: 25–62 years; mean age: 42.7 years) who had undergone neoadjuvant chemotherapy were enrolled prospectively	Compare the predicted residual tumor size and the predicted response on imaging and clinical examination with the residual tumor size and response on pathology	Agreement between the final response predictions and the responses measured by pathology had kappa values of 0.43 for clinical examination, 0.44 for mammography, 0.50 for sonography, and 0.82 for MRI	Predictions of response and residual tumor size made on MRI were better correlated with pathology assessments, suggesting MRI's potential as a sensitive early assessment tool for chemotherapy efficacy
5.	Early assessment with magnetic resonance imaging for prediction of pathologic response to neoadjuvant chemotherapy in triple-negative breast cancer: results from the phase III BrighTNess trial Golshan et al[6]	519 patients with stage II–III (T2-4 N0–2, or T1 N1–2) triple-negative breast cancer (TNBC) who underwent neoadjuvant systemic therapy (NST) as per protocol	Baseline and mid-treatment imaging and pathologic response data were available in 519 patients with stage II–III TNBC who underwent NST as per protocol. MRI was done after segment I therapy (12 weekly cycles of paclitaxel with or without concomitant carboplatin with or without veliparib) and before the first dose of doxorubicin/cyclophosphamide. MRI complete response (mCR) was defined as the disappearance of all target lesion(s) and MRI partial response (mPR) as a 50% reduction in the largest tumor diameter	MRI complete response (mCR) was observed in 22% of patients. MRI partial response (mPR) was observed in 32% of patients. Mid-treatment MRI had a positive predictive value (PPV) of 78% for demonstrating pathologic complete response (pCR) after completing NST for TNBC	Complete response on mid-treatment MRI in the BrighTNess trial had a PPV of 78% for demonstration of pCR after completion of NST in TNBC. However, a substantial proportion of patients with mPR or SD/PD also achieved a pCR
6.	MRI-based response patterns during neoadjuvant chemotherapy can predict pathological (complete) response in patients with breast cancer Goorts et al[7]	76 patients with 80 tumors (4 bilateral) were included. Consecutive patients treated with neoadjuvant chemotherapy (NAC) for primary invasive breast cancer from 2012 to 2015 who underwent breast MRI before, halfway through NAC, and after NAC was included. ER/PR+ HER2+ 16% ER/PR+ HER2− 60% ER-PR-HER2+ 8% ER-PR-HER2− 16%	All breast tumors were reassessed on MRI by two experienced breast radiologists and classified into six patterns: type 0 (complete radiologic response); type 1 (concentric shrinkage); type 2 (crumbling); type 3 (diffuse enhancement); type 4 (stable disease); type 5 (progressive disease). Percentages of tumors showing pathological complete response (pCR), > 50% tumor reduction, and > 50% tumor diameter reduction per MRI-based response pattern were calculated	There was a significant correlation between these MRI-based response patterns halfway through NAC and tumor reduction on pathology assessment. Type 0, type 1, or type 2 patterns halfway through NAC showed the highest tumor reduction rates on pathology assessment, with > 50% tumor reduction in 90, 78, and 65% of cases, respectively. In 83% of tumors with type 0 halfway through NAC, pathology assessment showed pCR. There was no significant correlation between MRI-based response patterns after NAC and tumor reduction rates on pathology assessment. In 41% of tumors with type 0 after NAC, pathology assessment showed pCR	MRI-based response patterns halfway through NAC can predict pathologic response more accurately than MRI-based response patterns after NAC. Complete radiological response halfway through NAC is associated with 83% pCR, while complete radiological response after NAC is correct in only 41% of cases
7.	Radiologic complete response (rCR) in contrast-enhanced magnetic resonance imaging (CE-MRI) after neoadjuvant chemotherapy for early breast cancer predicts recurrence-free survival but not pathologic complete response (pCR) Gampenrieder et al[8]	246 patients with early breast cancer (EBC), including those with locally advanced disease, who underwent contrast-enhanced MRI (CE-MRI) after neoadjuvant chemotherapy (NACT) Luminal A-like 23% Luminal B-like 12% HER2 +/HR− 13% HER2 +/HR+ 15% Triple-negative 37% cT1 24% cT2 57% cT3/4 19% cN0 49% cN+ 50% Nx 1%	Three radiologists, blinded to clinicopathologic data, reevaluated all MRI scans regarding the absence (radiologic complete remission; rCR) or presence (no-rCR) of residual contrast enhancement. Clinical and pathologic responses were compared categorically using Cohen's kappa statistic. The Kaplan–Meier method was used to estimate recurrence-free survival (RFS) and overall survival (OS)	Only 48% of rCR cases corresponded to a pCR, while 87% of patients with residual tumors observed on MRI were pathologically confirmed. Sensitivity to detect a pCR was 75%, while specificity to detect residual tumor and overall accuracy were 67 and 69%, respectively. The positive predictive value (PPV) was significantly lower in hormone-receptor (HR)-positive tumors compared with HR-negative tumors	Preoperative CE-MRI did not accurately predict pCR after NACT for EBC, especially not in HR-positive tumors. Concordance between rCR and pCR was low
8.	MRI does not predict pathological complete response after neoadjuvant chemotherapy for breast cancer Sener et al[9]	102 patients with breast cancer treated with neoadjuvant chemotherapy (NAC) from 2015 to 2018. Molecular subtypes of cancer for 102 patients. ER+ HER2− 23 ER+ HER2+ 25 ER− HER2− 31 ER− HER2+ 23	A single-institution retrospective analysis was performed, including clinical, radiographic, and pathologic parameters for all patients with breast cancer treated with NAC from 2015 to 2018. Radiographic complete response (rCR) was defined as the absence of suspicious MRI findings in the ipsilateral breast or lymph nodes	rCR was observed in 43.1% of patients, while pCR was observed in 40.1%. The PPV for MRI after NAC was 84.5%, and the NPV was 72.7%. The accuracy rate for MRI was 78.6%. However, 27.3% of patients with rCR had residual cancer on the pathologic specimen after surgical excision	rCR is not accurate enough to serve as a surrogate marker for pCR on MRI after NAC
9.	MRI performance in detecting pCR after neoadjuvant chemotherapy by molecular subtype of breast cancer Yu et al[11]	Patients with breast cancer who underwent MRI post-neoadjuvant chemotherapy (NAC). Ten studies involving 2,310 patients were included Triple negative HR +/HER2− HER2+ patients	Two reviewers searched Cochrane, PubMed, and EMBASE for articles published between 2013 and 2018 that examined MRI performance in detecting pCR post-NAC	TNBC: MRI performance in detecting pathologic complete response (pCR) varied. NPV ranged from 58 to 100%, PPV from 72.7 to 94.7%, sensitivity from 45.5 to 100%, and specificity from 49 to 94.4% across 446 patients. HR +/HER2− breast cancer- MRI performance in detecting pCR was inconsistent. NPV ranged from 29.4 to 100%, PPV from 21.4 to 95.1%, sensitivity from 43 to 100%, and specificity from 45 to 93% across 851 patients. HER2 + -enriched subtype of breast cancer—MRI accuracy in detecting pCR was not consistent, and its performance varied. NPV ranged from 62 to 94.6%, PPV from 34.9 to 72%, sensitivity from 36.2 to 83%, and specificity from 47 to 90% across 243 patients	The study suggests that MRI is not a reliable predictor of pCR by subtype, and larger standardized studies are needed. Clinicians may need to rely on alternative approaches such as biopsies of the tumor bed
10.	Accuracy of clinical examination, digital mammogram, ultrasound, and MRI in determining post-neoadjuvant pathologic tumor response in operable breast cancer patients Croshaw et al[10]	Sixty-two tumors in 61 patients with a mean age of 56 (range 34–87) years were evaluated. Large tumor size (T2 or greater) or locally advanced disease (stage III or greater) were included. invasive ductal carcinoma (IDC) = 50, invasive lobular cancer = 10 other = 2. They included all patients regardless of their tumor type or characteristics	A retrospective review was performed of data collected from patients treated with either neoadjuvant hormonal or chemotherapy between January 2005 and September 2010. Patients were evaluated by one of three surgical breast oncologists before neoadjuvant therapy and within 1 month before surgery by clinical breast examination (CBE), digital mammogram, breast ultrasound, and/or magnetic resonance imaging (MRI)	Overall accuracy ranged from 54% (CBE) to 80% (breast ultrasound). All modalities had a PPV greater than 75% for identifying the presence of residual disease. The PPV of each modality was generally higher in the younger patients. The NPV of all methods was less than 50%. The accuracy and NPV were compromised even further in younger patients. MRI is superior with regard to accuracy and PPV, but the NPV of MRIs remained poor at 65%	All measured tests are good at predicting the presence of disease on final pathology, but none can reliably predict a pathologic complete response

The first meta-analysis (of 44 studies) included patients who predominantly had stage II and III ductal breast cancers. It evaluated the utility of MRI in detecting residual breast cancer after neoadjuvant chemotherapy (NAC) and stated that MRI accurately detects it and is a better alternative to mammography. The American College of Radiology Imaging Network (ACRIN) 6657 trial by Scheel et al compared MRI with clinical examination and with mammography found that MRI was the most accurate for detecting pCR and also showed the highest association with final pathologic size in patients without pCR.[3]

A study by Shin et al observed that the predictions of residual tumor size and response to treatment evaluated on MRI were better correlated with pathology assessments, suggesting MRI's potential as a sensitive early assessment tool for chemotherapy efficacy. The responses measured by pathology had kappa values of 0.43 for clinical examination, 0.44 for mammography, 0.50 for sonography, and 0.82 for MRI.[4]

The second meta-analysis (of 34 studies) covered 1,932 pathologically confirmed cases of breast cancer. This analysis by Wu et al evaluated the effectiveness of diffusion-weighted MRI (DW-MRI) and contrast-enhanced MRI (CE-MRI) to assess and predict pathological response to NAC in patients with breast cancer.[5] It showed that DW-MRI has a sensitivity of 93% and specificity of 82%, while CE-MRI has a sensitivity of 68% and specificity of 91%. By using both DW-MRI and CE-MRI, there is a higher potential to improve the diagnostic performance of MRI in monitoring NAC.[5]

Golshan et al studied early assessment with MRI for the prediction of pathologic response to NAC in TNBC (BrighTNess trial). Baseline and mid-treatment imaging and pathologic response data were available for a total of 519 patients with stage II–III TNBC who were treated with NST as per protocol. MRI partial response (mPR) (≥50% reduction in the largest tumor diameter) was observed in 32% of patients. MRI complete response (mCR) was observed in 22% of patients[6]. The mid-treatment MRI findings showed a positive predictive value (PPV) of 78% in accurately indicating pathologic complete response (pCR) after completing NST for TNBC. A substantial proportion of patients with mPR also achieved a pCR. MRI-based response patterns halfway through NAC can predict pathologic response more accurately than MRI-based response patterns after NAC.[6]

Another study by Goorts et al included 76 patients, including 13 patients with TNBC (16%). Tumors showing complete radiologic response on MRI performed halfway through NST had the highest pathologic tumor response rates, with 83% demonstrating a pCR.[7] There was no significant correlation between MRI-based response patterns after NAC and tumor reduction rates on pathology assessment.

However, in a study by Gampenrieder et al, only 48% of patients with radiologic complete response (rCR) corresponded to a pCR, while 87% of patients with residual tumors observed on MRI were pathologically confirmed to have residual disease. Sensitivity for the detection of a pCR was 75%, while specificity for the detection of a residual tumor was 67% and overall accuracy was 69%. The PPV was significantly lower in hormone-receptor (HR)-positive tumors compared with HR-negative tumors. Preoperative CE-MRI did not accurately predict pCR after NACT for early breast cancer (EBC), especially not in HR-positive tumors.[8]

Sener et al observed rCR in 43% of patients, while pCR was observed in 40.1%. The PPV for MRI after NAC was 84.5%, and the NPV was 72.7%. The accuracy rate of MRI in correctly identifying pCR was 78.6%. However, 27.3% of patients with rCR had residual cancer on the pathologic specimen after surgical excision. Hence, they concluded that rCR is not accurate enough to serve as a surrogate marker for pCR on MRI after NAC.[9] A retrospective review by Croshaw et al reported similar findings, stating that while all evaluated tests are effective at predicting the presence of disease on final pathology, no single modality can reliably predict a pCR.[10]

Yu et al performed a literature review of 10 studies to determine MRI performance in detecting pCR after NAC by molecular subtype, including 2,310 patients published between 2013 and 2018.[11] This study suggests that MRI is not a reliable predictor of pCR by subtype. NPV ranged from 58 to 100%, PPV from 72.7 to 94.7%, sensitivity from 45.5 to 100%, and specificity from 49 to 94.4% across 446 patients. In HR +/HER2− breast cancer as well as in HER2 + -enriched subtype of breast cancer, MRI performance in detecting pCR was inconsistent. In the case of HR +/HER2− breast cancer, NPV ranged from 29.4 to 100%, PPV from 21.4 to 95.1%, sensitivity from 43 to 100%, and specificity from 45 to 93% across 851 patients. Whereas in HER2+ breast cancer, NPV ranged from 62 to 94.6%, PPV from 34.9 to 72%, sensitivity from 36.2 to 83%, and specificity from 47 to 90% across 243 patients. Yu et al are of the opinion that MRI is not a reliable predictor of pCR by subtype, and larger standardized studies are needed. They suggested that clinicians may need to rely on alternative approaches, such as biopsies of the tumor bed, to ensure more accurate assessment.[11]

A retrospective analysis evaluating the role of MRI in breast cancer patients concluded that a rCR identified by MRI is not sufficiently accurate to serve as a surrogate marker for pCR following NAC.[9] Pettit et al investigated whether MRI influences multidisciplinary treatment planning and whether it leads to higher mastectomy rates. They found that mastectomy rates tend to rise when MRI findings alone are used to guide surgical planning. To prevent overtreatment, they recommended that MRI-detected lesions should undergo biopsy for confirmation.[12] Another study noted that MRI following taxane-based therapy may overestimate response. MRI overestimated response to therapy in two-thirds of patients receiving taxane-containing chemotherapy.[13]

 

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Discussion

MRI scan has a sensitivity nearing 100% and specificity between 37 and 97%, making it a superior conventional imaging modality compared with ultrasonograms and mammograms.[14] Comparisons of clinical breast examination, mammography, ultrasonography, and MRI have found that MRI is the most accurate method for detecting tumor response and residual tumor.[15]

DW-MRI is a highly sensitive modality, while CE-MRI is highly specific in predicting the pathological response to NAC in breast cancer patients. The combined use of DW-MRI and CE-MRI has the potential to enhance diagnostic performance in monitoring NAC.[5]

However, MRI scans are not without limitations ([Table 2]). MRI can either overestimate or underestimate the size and extent of a lesion. Studies have shown that MRI overestimates the size of the lesion in 6 to 19% of cases and underestimates it in 7 to 28% of cases. Residual disease may be overestimated due to enhancement in benign areas of fibrosis, treatment-related changes, enlargement of benign masses, and residual nonenhancing masses representing treated tumors in cases of DCIS, as well as benign proliferative lesions such as intraductal papilloma or atypical ductal hyperplasia.[15] The extent of residual disease may be underestimated because tumors with non-mass morphology, such as invasive lobular carcinomas and luminal tumors, are challenging to measure accurately using MRI.[15] In addition, when cancer becomes fragmented in its response to chemotherapy, multiple foci can be scattered over a large geographic area.

Table 2 Factors that can lead to underestimation or overestimation of residual cancer on MRI after neoadjuvant chemotherapy (NAC), as well as factors affecting the reliability of MRI in this context

Factors	Factors leading to overestimation	Factors leading to underestimation
Chemotherapy type	N/A	Taxanes and antiangiogenic drugs can overestimate residual cancer[10] [20]
Tumor response	Significant inflammatory response and fibrotic reaction can overestimate residual cancer[15]	Heterogenous tumor response may result in underestimation[15]
Tumor characteristics	Superficial lesions may lead to overestimation[15]	Fragmented tumor response with multiple foci over a large geographic area may result in underestimation[15]
Inclusion of DCIS in PCR definition	Residual DCIS in the pCR definition can overestimate residual cancer[15]	N/A
Technical factors	Variability between institutions regarding MRI protocols, patient positioning and MRI hardware/software can affect reliability, leading to both overestimation and underestimation

Overestimating residual disease may lead to more extensive surgery, while missing residual disease can result in positive margins and necessitate surgical re-excision.[15]

In spite of its limited sensitivity and specificity, MRI remains the most precise imaging technique for evaluating tumor response to neoadjuvant therapy and planning surgery, surpassing mammography, ultrasound, and clinical examination.[15]

Can We Add Post-NST Pathological Examination through Needle Biopsy to the Post-NST MRI Imaging to Improve the Predictive Ability for pCR?

A VACB is a safe and minimally invasive procedure that removes a small sample of breast tissue for further examination. VACB is a possible solution that has a false-negative rate of less than 5% when done on patients with unicentric triple-negative or HER2-positive breast cancer when it is done with the following technical parameters: representative tissue sampling, use of multimodality breast imaging, removal of at least six core biopsy samples, documented clip removal, standardized histopathological processing and examination, and use of larger-gauge (≥9G) VACB needles.[1]

This procedure involves the insertion of a specialized biopsy needle into the breast through a small incision or cut in the skin, using a vacuum-powered instrument, and several tissue samples are taken. The vacuum draws tissue into the center of the needle and a rotating cutting device takes the samples. Postprocedure, the samples are retrieved from the center of the biopsy needle and sent to a laboratory for examination. Not surprisingly, VACB can convert some patients with near pCR following NST to pCR. For instance, in the study by Kuerer et al, 19 out of 50 patients had a disease detected on the VACB specimen. However, 7 out of these 19 patients (37%) had no residual cancer on surgical pathological examination (low PPV). A study from India by Hariharan et al attempted to test the predictive ability of non-VACB—the investigators used a 14G core needle biopsy to predict pCR following NST.[16] They studied the accuracy of tumor bed biopsy for predicting pCR after chemotherapy among women with breast cancer. They studied 65 women, of whom 94% were node-positive and 60% were hormone receptor-negative. Eligible patients with a complete or near-complete response to NACT as seen on a mammogram and ultrasound (US) were recruited. An MRI was performed for these patients for documentation. US-guided core biopsies of the tumor bed using a 14G needle were performed (minimum four in number), and the results were compared with the final histopathology report after surgery for standard performance parameters. They reported a pCR rate of 41.5 and 53.8% for the whole cohort and the hormone receptor–negative subgroup, respectively. The false-negative rate for core biopsy was 42.1%, with a negative predictive value of 59%. They suggest that ultrasound-guided 14G core needle biopsy of the tumor bed may not be a reliable predictor of pCR in the breast. Therefore, it appears that a routine core biopsy cannot provide the predictive accuracy of VACB (high negative predictive value).[16]

VACB has some limitations ([Table 3]). It is associated with adverse events like pain, bleeding, hematoma formation, skin injury, and dimple formation. Other possible complications include clip migration, which is seen more with superficial lesions and high specimen numbers.[17] To minimize the incidence of possible complications, VACB is not recommended in cases with scattered microcalcifications, lesions close to the skin, areola, nipple complex, or chest wall due to the difficulty in access and increased risk of skin dehiscence.[18]

Table 3 Limitations of vacuum-assisted core biopsy (VACB)

Aspect	Recommendations and complications
Recommendations	Not recommended in cases with scattered MCC, lesions close to the skin, areola and nipple complex, or chest wall due to access difficulty and increased risk of skin dehiscence[17]
Complication rate	Park et al: 25% complications, including bleeding, hematoma, skin injury, dimple formation, and pneumothorax[14] Hu et al: Pain (22.6%), hematoma formation (9.7%), ecchymosis (3.2%)[21]
Risk factors for bleeding	USG-VAB has a slightly higher risk of bleeding compared with SVAB (stereotactic Vacuum-Assisted Breast Biopsy) due to the lack of breast compression during the US-guided procedure[22]
Other complications	Clip migration, more common with superficial lesions, high Specimen number.[23]
Prevention of skin injury	Berná-Serna et al used a simple, safe technique to prevent skin injury during the VABB by inserting a spinal needle between the skin and the mass[24]

Interestingly, the study by Kuerer et al reported that a significant number of patients with breast cancer who attained a complete response to chemotherapy on pathological examination confirmed with VACB did not exhibit a radiological complete response using mammography and ultrasound scan. This data underscore the essential need for image-guided biopsy, possibly with a better imaging tool like an MRI scan, to guarantee the accurate selection of eligible patients for omitting breast surgery.[1]

While MRI may offer superior accuracy compared with other methods, relying solely on it may not be sufficient to ascertain pCR in all types of breast cancers. However, utilizing MRI in conjunction with biopsy may be a promising technique to accurately identify a specific subset of patients with small-sized tumors for whom surgery can be avoided.

Utilizing MRI-guided VACB enhances the diagnostic information obtained from breast MRI. This approach enables precise biopsies of even small lesions, ensuring increased certainty in obtaining representative tissue samples. The ability to cross-verify the removal of the entire enhancing lesion or a portion thereof further contributes to the accuracy of the diagnostic process. Moreover, this method has been demonstrated to be minimally invasive.[18] Advances in medical technology, exemplified by the development of tools such as breast coils, devices for breast fixation, biopsy compression devices, needle guides, and non-ferrous magnetic needles, have effectively tackled numerous challenges associated with MRI-guided procedures. These innovations have played a crucial role in facilitating MRI-guided VACB.[13]

Drawbacks of MRI-guided VACB include issues such as needle artifacts and tissue displacement during needle insertion ([Table 4]). Another challenge with MRI-guided biopsy is the limited window of time available to the operator for visualizing a lesion after injecting the contrast agent. Consequently, this procedure has traditionally been used for lesions smaller than 1 cm.[14]

Table 4 Limitations of MRI-guided VACB[14]

Drawbacks of MRI-guided VACB	Reasons for limited popularity
Needle artifacts and tissue displacement	Limited popularity due to technical challenges and patient positioning
Patient needs to be moved from the magnet	Procedure often requires lying face down on a movable table
Limited interior access	Limited window of time for visualizing lesions after contrast injection
Traditionally used for lesions < 1 cm

 

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Conclusion

Based on our assessment of the various studies, combining an MRI scan of the breast post-NST with VACB post-NST would be the best method to select patients for omitting cancer surgery. The predictive ability will likely be greater for patients with smaller-sized TNBC or HER2-positive diseases that are node-negative. Kuerer et al's hypothesis-generating study can be a foundation for larger clinical studies that examine the combined use of MRI scans with VACB following NST in predicting pCR and therefore select patients who can be safely spared from undergoing breast cancer surgery. Such a therapeutic strategy could indeed bring forth a paradigm shift in the care of women with breast cancer.

 

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Conflict of Interest

None declared.

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Artikel online veröffentlicht:
08. September 2025