Nonoperative Management for Invasive Breast Cancer After Neoadjuvant Systemic Therapy: Conceptual Basis and Fundamental International Feasibility Clinical Trials

A nomogram to predict the pathological complete response in patients with breast cancer based on the TILs-US score

BACKGROUND

The tumor-infiltrating lymphocytes-ultrasonography score is a calculation system for predicting lymphocyte-predominant breast cancers in surgical specimens. A nomogram based on the tumor-infiltrating lymphocytes-ultrasonography score was developed to predict the pathological complete response in breast cancer treated with neoadjuvant chemotherapy.

METHODS

A retrospective evaluation was conducted on 118 patients with breast cancer treated with neoadjuvant chemotherapy at Hiroshima University Hospital. Tumor-infiltrating lymphocytes-ultrasonography scores ≥4 were classified as high. A nomogram was developed using a stepwise logistic regression model for pathological complete response (ypT0 ypN0), based on the smallest Akaike information criterion. The predictive ability and clinical usefulness of the nomogram were also evaluated.

RESULTS

Among 118 patients, 34 (28.8%) achieved a pathological complete response, and 52 (44.1%) exhibited high tumor-infiltrating lymphocytes-ultrasonography. In multivariate logistic regression analysis, high tumor-infiltrating lymphocytes-ultrasonography (odds ratio, 6.01; P < 0.001), clinical complete response (odds ratio, 4.83; P = 0.004) and hormone receptor (odds ratio, 3.48; P = 0.038) were independent predictors of pathological complete response. A nomogram based on tumor-infiltrating lymphocytes-ultrasonography score, clinical complete response, hormone receptor and clinical N status was developed. The nomogram showed an area under the curve of 0.831 and a bias-corrected area under the curve of 0.809. The calibration plot showed a good fit between the expected and actual pathological complete response values. Decision curve analysis also showed the clinical utility of the nomogram for predicting pathological complete responses.

CONCLUSIONS

A nomogram based on the tumor-infiltrating lymphocytes-ultrasonography score exhibited a favorable predictive ability for pathological complete response in patients with breast cancer, which can be useful in predicting the residual disease status after neoadjuvant chemotherapy.

HSD17B4 methylation enhances glucose dependence of BT-474 breast cancer cells and increases lapatinib sensitivity

PURPOSE

HER2-positive breast cancer has a high chance of achieving pathological complete response when HSD17B4, responsible for peroxisomal β-oxidation of very long-chain fatty acids (VLCFA) and estradiol, is methylation-silenced. Here, we aimed to identify the underlying molecular mechanism.

METHODS

Using a HER2-positive breast cancer cell line, BT-474, control and knock-out (KO) clones were obtained. Metabolic characteristics were analyzed using a Seahorse Flux analyzer.

RESULTS

HSD17B4 KO suppressed cellular proliferation, and enhanced sensitivity to lapatinib approximately tenfold. The KO led to accumulation of VLCFA and a decrease of polyunsaturated fatty acids (PUFAs), such as docosahexaenoic acid (DHA) and arachidonic acid. HSD17B4 KO increased Akt phosphorylation, possibly via decreased DHA, and genes involved in oxidative phosphorylation (OxPhos) and electron transport chain (ETC) were upregulated. Increased mitochondrial ATP production in the KO cells was confirmed by extracellular flux analyzer. Increased OxPhos led to severe dependence of the KO cells on pyruvate from glycolysis. Suppression of glycolysis by lapatinib led to severe delayed suppression of OxPhos in KO cells.

CONCLUSION

HSD17B4 KO in BT-474 cells caused a decrease of PUFAs, increased Akt phosphorylation, enhanced glucose dependence of OxPhos, and increased sensitivity to inhibition of HER2, upstream of Akt. This mechanism may be applicable to other HER2-positive glucose-dependent breast cancer cells with HSD17B4 silencing.

Surgical Planning after Neoadjuvant Treatment in Breast Cancer: A Multimodality Imaging-Based Approach Focused on MRI

Neoadjuvant chemotherapy (NACT) today represents a cornerstone in the treatment of locally advanced breast cancer and highly chemo-sensitive tumors at early stages, increasing the possibilities of performing more conservative treatments and improving long term outcomes. Imaging has a fundamental role in the staging and prediction of the response to NACT, thus aiding surgical planning and avoiding overtreatment. In this review, we first examine and compare the role of conventional and advanced imaging techniques in preoperative T Staging after NACT and in the evaluation of lymph node involvement. In the second part, we analyze the different surgical approaches, discussing the role of axillary surgery, as well as the possibility of non-operative management after-NACT, which has been the subject of recent trials. Finally, we focus on emerging techniques that will change the diagnostic assessment of breast cancer in the near future.

[Breast Imaging Reporting and Data System (BI-RADS): Advantages and Limitations]

Breast Imaging Reporting and Data System (BI-RADS) is a communication and data tracking system that standardizes and controls the quality of reporting by presenting lexicon descriptors, assessment categories, and recommendations for managing breast lesions. Using standardized terminology recommended by BI-RADS, radiologists can concisely and reproducibly communicate breast imaging results to clinicians. They can also provide the estimated malignant probability of the lesions found and guide management for them by determining the final assessment category. The limitations of BI-RADS 5th edition currently in use are that there are some areas for which standardized terminologies still need to be established, and that the diagnostic criteria of MRI assessment categories 3 and 4 are ambiguous compared to those for mammography or ultrasound. The next revision of BI-RADS is expected to include solutions for overcoming current limitations.

Estimating the Benefit of Preoperative Systemic Therapy to Reduce the Extent of Breast Cancer Surgery: Current Standard and Future Directions

Once reserved for locally advanced tumors which were deemed inoperable at presentation, preoperative systemic therapy (PST) is nowadays increasingly used to treat early breast cancer. PST allows for in vivo assessment of tumor response, for tailoring of adjuvant systemic therapy and for de-escalation of breast and the axillary surgery. Increased rates of pathological complete response together with more accurate response assessment and surgical planning have led to a significant reduction in surgical morbidity. While surgical assessment remains the standard of care, ongoing studies are evaluating whether surgery can be omitted in patients who achieve a complete pathological response. In this chapter, I will review the impact of PST on surgical de-escalation and the data supporting the safety of this approach.

Assessment and Response to Neoadjuvant Treatments in Breast Cancer: Current Practice, Response Monitoring, Future Approaches and Perspectives

Neoadjuvant treatments (NAT) for breast cancer (BC) consist in the administration of chemotherapy-more rarely endocrine therapy-before surgery. Firstly, it was introduced 50 years ago to downsize locally advanced (inoperable) BCs. NAT are now widespread and so effective to be used also at the early stage of the disease. NAT are heterogeneous in terms of therapeutic patterns, class of used drugs, dosage, and duration. The poly-chemotherapy regimen and administration schedule are established by a multi-disciplinary team, according to the stage of disease, the tumor subtype and the age, the physical status, and the drug sensitivity of BC patients. Consequently, an accurate monitoring of treatment response can provide significant clinical advantages, such as the treatment de-escalation in case of early recognition of complete response or, on the contrary, the switch to an alternative treatment path in case of early detection of resistance to the ongoing therapy. Future is going toward increasingly personalized therapies and the prediction of individual response to treatment is the key to practice customized care pathways, preserving oncological safety and effectiveness. To gain such goal, the development of an accurate monitoring system, reproducible and reliable alone or as part of more complex diagnostic algorithms, will be promising.

Staging Breast Cancer with MRI, the T. A Key Role in the Neoadjuvant Setting

Breast cancer (BC) is the most common cancer among women worldwide. Neoadjuvant chemotherapy (NACT) indications have expanded from inoperable locally advanced to early-stage breast cancer. Achieving a pathological complete response (pCR) has been proven to be an excellent prognostic marker leading to better disease-free survival (DFS) and overall survival (OS). Although diagnostic accuracy of MRI has been shown repeatedly to be superior to conventional methods in assessing the extent of breast disease there are still controversies regarding the indication of MRI in this setting. We intended to review the complex literature concerning the tumor size in staging, response and surgical planning in patients with early breast cancer receiving NACT, in order to clarify the role of MRI. Morphological and functional MRI techniques are making headway in the assessment of the tumor size in the staging, residual tumor assessment and prediction of response. Radiomics and radiogenomics MRI applications in the setting of the prediction of response to NACT in breast cancer are continuously increasing. Tailored therapy strategies allow considerations of treatment de-escalation in excellent responders and avoiding or at least postponing breast surgery in selected patients.

Visual Evaluation of Ultrafast MRI in the Assessment of Residual Breast Cancer after Neoadjuvant Systemic Therapy: A Preliminary Study Association with Subtype

The purpose of this study was to investigate the diagnostic performance of ultrafast DCE (UF-DCE) MRI after the completion of neoadjuvant systemic therapy (NST) in breast cancer. In this study, MR examinations of 55 post-NST breast cancers were retrospectively analyzed. Residual tumor sizes were measured in the 20th phase of UF-DCE MRI, early and delayed phases of conventional DCE MRI, and high spatial-resolution CE MRI (UF, early, delayed, and HR, respectively). The diagnostic performance for the detection of residual invasive cancer was calculated by ROC analysis. The size difference between MRI and pathological findings was analyzed using the Wilcoxon signed-rank test with the Bonferroni correction. The overall AUC was highest for UF (0.86 and 0.88 for readers 1 and 2, respectively). The difference in imaging and pathological sizes for UF (5.7 ± 8.2 mm) was significantly smaller than those for early, delayed, and HR (p < 0.01). For luminal subtype breast cancer, the size difference was significantly smaller for UF and early than for delayed (p < 0.01). UF-DCE MRI demonstrated higher AUC and specificity for the more accurate detection of residual cancer and the visualization of tumor extent than conventional DCE MRI.

Innovative Standards in Oncoplastic Breast Conserving Surgery: From Radical Mastectomy to Extreme Oncoplasty

BACKGROUND

Oncoplastic breast conserving surgery (OBCS), which is the current procedure of choice for eligible BC patients, describes a philosophy that prioritizes oncologic and cosmetic outcomes. However, knowledge gaps regarding training, acceptance, and practice preclude standardization and make it difficult to design algorithmic guidelines to optimize individualized management in the era of precision medicine.

SUMMARY

The harmony between patient expectations and oncologic goals creates the state of the art of OBCS. Nevertheless, to achieve these goals, multidisciplinary approach is a must. Surgical decisions require a comprehensive evaluation including patient factors, tumor biology, genetics, technical considerations, and adjunct therapies. Moreover, the quality-of-life (QOL) issues should be considered as the highest level of priority with a shared decision making instituted on realistic discussions with the patient.

KEY MESSAGES

The standardization in OBCS should be initiated via defining a breast surgeon who should gain theorical and practical competence on techniques via national or international educational programs. The algorithmic patient assessment with appropriate documentation before and after surgery should be established. A simple and safe global lexicon should be designed regarding techniques to be proposed and quality metrics to be considered. Additionally, international multicenter prospective trials should be instituted to overcome knowledge gaps. It is evident that OBCS is the perfect union of science with art. Nevertheless, at the very end, the question is not the nature of the surgeon/artist who would be the extremist, the innovator, or the conservative, but the patient's satisfaction, prognosis, and QOL that conclude the cascade of state of the art of OBCS.

Breast Cancer Surgery: New Issues

Since ancient times, breast cancer treatment has crucially relied on surgeons and clinicians making great efforts to find increasingly conservative approaches to cure the tumor. In the Halstedian era (mid-late 19th century), the predominant practice consisted of the radical and disfiguring removal of the breast, much to the detriment of women's psycho-physical well-being. Thanks to enlightened scientists such as Professor Umberto Veronesi, breast cancer surgery has since impressively progressed and adopted a much more conservative approach. Over the last three decades, a better understanding of tumor biology and of its significant biomarkers has made the assessment of genetic and molecular profiles increasingly important. At the same time, neo-adjuvant treatments have been introduced, and great improvements in genetics, imaging technologies and in both oncological and reconstructive surgical techniques have been made. The future of breast cancer management must now rest on an ever more precise and targeted type of surgery that, through an increasingly multidisciplinary and personalized approach, can ensure oncological radicality while offering the best possible quality of life.

Toward omitting sentinel lymph node biopsy after neoadjuvant chemotherapy in patients with clinically node-negative breast cancer

BACKGROUND

The nodal positivity rate after neoadjuvant chemotherapy (ypN+) in patients with clinically node-negative (cN0) breast cancer is low, especially in those with a pathological complete response of the breast. The aim of this study was to identify characteristics known before surgery that are associated with achieving ypN0 in patients with cN0 disease. These characteristics could be used to select patients in whom sentinel lymph node biopsy may be omitted after neoadjuvant chemotherapy.

METHODS

This cohort study included patients with cT1-3 cN0 breast cancer treated with neoadjuvant chemotherapy followed by breast surgery and sentinel node biopsy between 2013 and 2018. cN0 was defined by the absence of suspicious nodes on ultrasound imaging and PET/CT, or absence of tumour cells at fine-needle aspiration. Univariable and multivariable logistic regression analyses were performed to determine predictors of ypN0.

RESULTS

Overall, 259 of 303 patients (85.5 per cent) achieved ypN0, with high rates among those with a radiological complete response (rCR) on breast MRI (95·5 per cent). Some 82 per cent of patients with hormone receptor-positive disease, 98 per cent of those with triple-negative breast cancer (TNBC) and all patients with human epidermal growth factor receptor 2 (HER2)-positive disease who had a rCR achieved ypN0. Multivariable regression analysis showed that HER2-positive (odds ratio (OR) 5·77, 95 per cent c.i. 1·91 to 23·13) and TNBC subtype (OR 11·65, 2·86 to 106·89) were associated with ypN0 status. In addition, there was a trend toward ypN0 in patients with a breast rCR (OR 2·39, 0·95 to 6·77).

CONCLUSION

The probability of nodal positivity after neoadjuvant chemotherapy was less than 3 per cent in patients with TNBC or HER2-positive disease who achieved a breast rCR on MRI. These patients could be included in trials investigating the omission of sentinel node biopsy after neoadjuvant chemotherapy.

Minimally Invasive Complete Response Assessment of the Breast After Neoadjuvant Systemic Therapy for Early Breast Cancer (MICRA trial): Interim Analysis of a Multicenter Observational Cohort Study

BACKGROUND

The added value of surgery in breast cancer patients with pathological complete response (pCR) after neoadjuvant systemic therapy (NST) is uncertain. The accuracy of imaging identifying pCR for omission of surgery, however, is insufficient. We investigated the accuracy of ultrasound-guided biopsies identifying breast pCR (ypT0) after NST in patients with radiological partial (rPR) or complete response (rCR) on MRI.

METHODS

We performed a multicenter, prospective single-arm study in three Dutch hospitals. Patients with T1-4(N0 or N +) breast cancer with MRI rPR and enhancement ≤ 2.0 cm or MRI rCR after NST were enrolled. Eight ultrasound-guided 14-G core biopsies were obtained in the operating room before surgery close to the marker placed centrally in the tumor area at diagnosis (no attempt was made to remove the marker), and compared with the surgical specimen of the breast. Primary outcome was the false-negative rate (FNR).

RESULTS

Between April 2016 and June 2019, 202 patients fulfilled eligibility criteria. Pre-surgical biopsies were obtained in 167 patients, of whom 136 had rCR and 31 had rPR on MRI. Forty-three (26%) tumors were hormone receptor (HR)-positive/HER2-negative, 64 (38%) were HER2-positive, and 60 (36%) were triple-negative. Eighty-nine patients had pCR (53%; 95% CI 45-61) and 78 had residual disease. Biopsies were false-negative in 29 (37%; 95% CI 27-49) of 78 patients. The multivariable associated with false-negative biopsies was rCR (FNR 47%; OR 9.81, 95% CI 1.72-55.89; p = 0.01); a trend was observed for HR-negative tumors (FNR 71% in HER2-positive and 55% in triple-negative tumors; OR 4.55, 95% CI 0.95-21.73; p = 0.058) and smaller pathological lesions (6 mm vs 15 mm; OR 0.93, 95% CI 0.87-1.00; p = 0.051).

CONCLUSION

The MICRA trial showed that ultrasound-guided core biopsies are not accurate enough to identify breast pCR in patients with good response on MRI after NST. Therefore, breast surgery cannot safely be omitted relying on the results of core biopsies in these patients.

Can breast MRI and adjunctive Doppler ultrasound improve the accuracy of predicting pathological complete response after neoadjuvant chemotherapy?

BACKGROUND

To examine the accuracy of MRI and Doppler ultrasound (US) for detecting residual tumor after neoadjuvant chemotherapy (NAC) for breast cancer and evaluate whether adjunctive Doppler US improves the MRI accuracy.

METHODS

We reviewed 276 invasive breast cancer cases treated with NAC. Tumors were classified into four subtypes based on estrogen receptor and HER2 status. Response to NAC was evaluated using contrast-enhanced MRI and Doppler US. Residual Doppler flow was assumed to indicate a residual tumor. MRI and Doppler findings were compared with the histopathological findings of resected specimens. Pathological complete response (pCR) was defined as neither in situ nor invasive cancer left.

RESULTS

Of the 276 tumors, imaging complete responses were observed using MRI and Doppler US in 62 (22%) and 111 (40%), respectively, whereas pCR was achieved in 44 (16%). MRI and Doppler US predicted residual tumor with 88% and 69% sensitivity, 80% and 91% specificity, 87% and 73% accuracy, 96% and 98% PPV, and 56% and 36% NPV, respectively. The accuracies of MRI and Doppler US were significantly higher for HER2-negative than HER2-positive tumors (p < 0.001 and p = 0.043, respectively). Seven (26%) of 27 false-negative cases identified by MRI were correctly diagnosed as positives with adjunctive Doppler US.

CONCLUSIONS

Although MRI accurately detected residual tumor with 87% accuracy, this was still not sufficient to meet clinical demands and differed with tumor subtype. Adjunctive Doppler US in cases that appear to show a complete response on MRI might reduce chances of false negatives and increase the NPV of MRI for predicting residual tumor.

Eliminating the breast cancer surgery paradigm after neoadjuvant systemic therapy: current evidence and future challenges

In patients with operable early breast cancer, neoadjuvant systemic treatment (NST) is a standard approach. Indications have expanded from downstaging of locally advanced breast cancer to facilitate breast conservation, to in vivo drug-sensitivity testing. The pattern of response to NST is used to tailor systemic and locoregional treatment, that is, to escalate treatment in nonresponders and de-escalate treatment in responders. Here we discuss four questions that guide our current thinking about 'response-adjusted' surgery of the breast after NST. (i) What critical diagnostic outcome measures should be used when analyzing diagnostic tools to identify patients with pathologic complete response (pCR) after NST? (ii) How can we assess response with the least morbidity and best accuracy possible? (iii) What oncological consequences may ensue if we rely on a nonsurgical-generated diagnosis of, for example, minimally invasive biopsy proven pCR, knowing that we may miss minimal residual disease in some cases? (iv) How should we design clinical trials on de-escalation of surgical treatment after NST?

Predictive factors of pathologically node-negative disease for HER2 positive and triple-negative breast cancer after neoadjuvant therapy

Background

With the improvement of the efficacy of neoadjuvant therapy (NAT) that is guided by molecular subtypes, the rate of pathologically node-negative disease after NAT (ypN0) is increasing for HER2 positive (HER2+) and triple-negative (TN) breast cancer patients. The necessity of axillary surgery for patients with high ypN0 has been questioned. This study aimed to identify patients among HER2+ and TN breast cancer with low risk for axillary metastases after NAT, and, perhaps, they are suitable for selective elimination of axillary surgery staging.

Methods

From January 2010 to August 2018, 865 breast cancer patients who underwent NAT were included in this retrospective clinical study, and 184 patients (21.3%,184/865) suffered from TN and HER2+ breast cancer and received full-course NAT. The correlation among clinicopathological characteristics of HER2+ and TN breast cancer and ypN0 were analyzed.

Results

Among the 184 HER2+ and TN breast cancer patients, tumor staging, lymph node staging and Ki-67 before NAT, clinically node-negative disease after NAT (ycN0), and breast radiologic and pathologic complete response (bpCR) were correlated with ypN0 (P<0.05). Lymph node staging before NAT (OR =0.363, P<0.001), ycN0 (OR =4.995, P<0.001) and bpCR (OR =11.285, P<0.001) were the independent effects of ypN0. The ypN0 rate after NAT in cN0/1 patients with bpCR and ycN0 (97.6%, 40/41) was significantly higher than that in cN2/3 patients (62.5%, 10/16) (P<0.001). Among the 37 patients with initial nodal ultrasonography showing cN0 disease, 17 of 17 (100.0%) with and 18 of 20 (90.0%) without bpCR had no evidence of residual nodal disease (P=0.178). Among the 42 patients with cN1 to ycN0, 23 of 24 (95.8%) with and 10 of 18 (55.6%) without bpCR had no evidence of residual nodal disease (P<0.001). Patients without bpCR had a relative risk for nodal residual metastases of 10.560 (95% CI: 2.720-41.003; P<0.001) compared with those with bpCR in cN1 group.

Conclusions

In terms of HER2+ and TN breast cancer patients, clinical lymph node staging before NAT, ycN0 and bpCR were the independent predictors of ypN0. bpCR was highly correlated with nodal status after NAT. The risk of axillary lymph nodes residual metastases after NAT in the patients of bpCR with cN0 and cN1 to ycN0 was less than 5%, thus making it possible to selectively avoid axillary surgery.

Tumor-Infiltrating Lymphocytes in Low-Risk Patients With Breast Cancer Treated With Single-Dose Preoperative Partial Breast Irradiation

PURPOSE

Preoperative partial breast irradiation (PBI) has the potential to induce tumor regression. We evaluated the differences in the numbers of preirradiation tumor infiltrating lymphocytes (TILs) between responders and nonresponders after preoperative PBI in low-risk patients with breast cancer. Furthermore, we evaluated the change in number of TILs before and after irradiation.

METHODS AND MATERIALS

In the prospective ABLATIVE study, low-risk patients with breast cancer underwent treatment with single-dose preoperative PBI (20 Gy) to the tumor and breast-conserving surgery after 6 or 8 months. In the preirradiation diagnostic biopsy and postirradiation resection specimen, numbers of TILs in 3 square regions of 450 × 450 μm were counted manually. TILs were visualized with CD3, CD4, and CD8 immunohistochemistry. Differences in numbers of preirradiation TILs between responders and nonresponders were tested using Mann-Whitney U test. Responders were defined as pathologic complete or near-complete response, and nonresponders were defined "as all other response." Changes in numbers of TILs after preoperative PBI was evaluated with the Wilcoxon signed rank test.

RESULTS

Preirradiation tissue was available from 28 patients, postirradiation tissue from 29 patients, resulting in 22 pairs of preirradiation and postirradiation tissue. In these 35 patients, 15 had pathologic complete response (43%), 11 had a near-complete response (31%), 7 had a partial response (20%), and 2 had stable disease (6%). The median numbers of CD3⁺ TILs, CD4⁺ TILs, and CD8⁺ TILs in the preirradiation tumor tissue were 49 (interquartile range [IQR], 36-80), 45 (IQR, 28-57), and 19 (IQR, 8-35), respectively. The number of preirradiation TILs did not differ significantly between responders and nonresponders. The median numbers of CD3⁺ TILs, CD4⁺ TILs, and CD8⁺ TILs in postirradiation tumor tissue were 17 (IQR, 13-31), 26 (IQR, 16-35), and 7 (IQR, 5-11), respectively.

CONCLUSIONS

After preoperative PBI in this limited cohort, the number of TILs in tumor tissue decreased. No differences in numbers of preirradiation TILs between responders and nonresponders were observed.

Prognostic and predictive value of circulating tumor DNA during neoadjuvant chemotherapy for triple negative breast cancer

Response to neoadjuvant chemotherapy (NAC) in triple negative breast cancer (TNBC) is highly prognostic and determines whether adjuvant chemotherapy is needed if residual tumor is found at surgery. To evaluate the predictive and prognostic values of circulating tumor DNA (ctDNA) in this setting, we analyzed tumor and serial bloods from 26 TNBC patients collected prior, during, and after NAC. Individual digital droplet PCR assays were developed for 121 variants (average 5/patient) identified from tumor sequencing, enabling ctDNA detection in 96% of patients at baseline. Mutant allele frequency at baseline was associated with clinical characteristics. Levels drastically fell after one cycle of NAC, especially in patients whose tumors would go on to have a pathological complete response (pCR), but then rose significantly before surgery in patients with significant residual tumor at surgery (p = 0.0001). The detection of ctDNA early during treatment and also late at the end of NAC before surgery was strongly predictive of residual tumor at surgery, but its absence was less predictive of pCR, especially when only TP53 variants are considered. ctDNA detection at the end of neoadjuvant chemotherapy indicated significantly worse relapse-free survival (HR = 0.29 (95% CI 0.08–0.98), p = 0.046), and overall survival (HR = 0.27 95% CI 0.075–0.96), p = 0.043). Hence, individualized multi-variant ctDNA testing during and after NAC prior to surgery has prognostic and predictive value in early TNBC patients.

The Diagnostic Performance of Minimally Invasive Biopsy in Predicting Breast Pathological Complete Response After Neoadjuvant Systemic Therapy in Breast Cancer: A Meta-Analysis

Background: Neoadjuvant systemic therapy (NST) is commonly used in patients with early stage breast cancer before definitive surgery. The standard diagnostic approach for pathologic complete response (pCR) of the breast is breast surgery and pathologic examination. In recent years, several trials investigated the predictive value of image-guided minimally invasive biopsy (MIB) for breast pCR after NST. This study conducted a meta-analysis to evaluate the diagnostic accuracy of MIB.

Materials and Methods: We identified relevant research reports in online databases through February 2020. The Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool was used to evaluate the quality of included trials. We extracted relevant data and constructed a 2 × 2 contingency table to analyze the predictive accuracy of MIB for breast pCR. Subgroup analyses and meta-regressions were also performed to investigate potential causes of heterogeneity.

Results: Nine trials (with 1,030 breast cancer patients) were included in this meta-analysis. The pooled sensitivity and specificity of MIB were 0.72 [95% confidence interval (CI): 0.61–0.81] and 0.99 (95% CI: 0.89–1.00), respectively. By combining relevant data, there were no significant differences in sensitivity or specificity among different molecular subtypes of breast cancer (P > 0.05). Subgroup analyses and meta-regressions implied that trials with responses not limited to clinical complete response (cCR) had a significantly higher accuracy of MIB than those with only cCR (RDOR: 7.65; 95% CI: 1.05–55.46; P = 0.046).

Conclusion: Current image-guided MIB methods are not accurate enough in terms of predicting breast pCR after NST. It is of utmost clinical importance to standardize the MIB procedure and incorporate other factors into the evaluation in order to improve the accuracy to an acceptable level.

A machine learning model that classifies breast cancer pathologic complete response on MRI post-neoadjuvant chemotherapy

Background

For breast cancer patients undergoing neoadjuvant chemotherapy (NAC), pathologic complete response (pCR; no invasive or in situ) cannot be assessed non-invasively so all patients undergo surgery. The aim of our study was to develop and validate a radiomics classifier that classifies breast cancer pCR post-NAC on MRI prior to surgery.

Methods

This retrospective study included women treated with NAC for breast cancer from 2014 to 2016 with (1) pre- and post-NAC breast MRI and (2) post-NAC surgical pathology report assessing response. Automated radiomics analysis of pre- and post-NAC breast MRI involved image segmentation, radiomics feature extraction, feature pre-filtering, and classifier building through recursive feature elimination random forest (RFE-RF) machine learning. The RFE-RF classifier was trained with nested five-fold cross-validation using (a) radiomics only (model 1) and (b) radiomics and molecular subtype (model 2). Class imbalance was addressed using the synthetic minority oversampling technique.

Results

Two hundred seventy-three women with 278 invasive breast cancers were included; the training set consisted of 222 cancers (61 pCR, 161 no-pCR; mean age 51.8 years, SD 11.8), and the independent test set consisted of 56 cancers (13 pCR, 43 no-pCR; mean age 51.3 years, SD 11.8). There was no significant difference in pCR or molecular subtype between the training and test sets. Model 1 achieved a cross-validation AUROC of 0.72 (95% CI 0.64, 0.79) and a similarly accurate (P = 0.1) AUROC of 0.83 (95% CI 0.71, 0.94) in both the training and test sets. Model 2 achieved a cross-validation AUROC of 0.80 (95% CI 0.72, 0.87) and a similar (P = 0.9) AUROC of 0.78 (95% CI 0.62, 0.94) in both the training and test sets.

Conclusions

This study validated a radiomics classifier combining radiomics with molecular subtypes that accurately classifies pCR on MRI post-NAC.

Preoperative evaluation of mammographic microcalcifications after neoadjuvant chemotherapy for breast cancer

AIM

To assess the predictive value of preoperative residual mammographic microcalcifications for residual tumours after neoadjuvant chemotherapy (NAC) for breast cancer.

MATERIALS AND METHODS

This single-centre retrospective study included breast cancer patients who underwent NAC and demonstrated suspicious microcalcifications within or near the tumour bed on mammography from June 2015 to August 2018. The residual microcalcifications and remnant lesion on magnetic resonance imaging (MRI) were correlated with histopathological findings of residual tumours and immunohistochemical markers.

RESULTS

A total of 96 patients were included. Ten patients achieved pathological complete response (pCR) and previous suspicious microcalcifications were associated with benign pathology in 10.4% (10/96) of the patients. In the remaining 86 patients who did not achieve pCR, 61.5% (59/96) of the residual microcalcifications were associated with invasive or in situ carcinoma and 28.1% (27/96) with benign pathology. Hormone receptor-positive (HR⁺) patients had the highest proportion of residual malignant microcalcifications compared to HR^- patients (48.9% versus 13.5%, respectively; p=0.019). MRI correlated better than residual microcalcifications on mammography in predicting residual tumour extent in all subtypes (ICC=0.709 versus 0.365). MRI also showed higher correlation with residual tumour size for the HR^-/HER2⁺ and HR^-/HER2^- subtype (ICC=0.925 and 0.876, respectively).

CONCLUSION

The extent of microcalcifications on mammography after NAC did not correlate with the extent of residual cancer in 38.5% of women. Regardless of the extent of microcalcifications, residual tumour extent on MRI after NAC and molecular subtype could be an accurate tool in evaluating residual cancer after NAC.

IASLC Multidisciplinary Recommendations for Pathologic Assessment of Lung Cancer Resection Specimens After Neoadjuvant Therapy

Currently, there is no established guidance on how to process and evaluate resected lung cancer specimens after neoadjuvant therapy in the setting of clinical trials and clinical practice. There is also a lack of precise definitions on the degree of pathologic response, including major pathologic response or complete pathologic response. For other cancers such as osteosarcoma and colorectal, breast, and esophageal carcinomas, there have been multiple studies investigating pathologic assessment of the effects of neoadjuvant therapy, including some detailed recommendations on how to handle these specimens. A comprehensive mapping approach to gross and histologic processing of osteosarcomas after induction therapy has been used for over 40 years. The purpose of this article is to outline detailed recommendations on how to process lung cancer resection specimens and to define pathologic response, including major pathologic response or complete pathologic response after neoadjuvant therapy. A standardized approach is recommended to assess the percentages of (1) viable tumor, (2) necrosis, and (3) stroma (including inflammation and fibrosis) with a total adding up to 100%. This is recommended for all systemic therapies, including chemotherapy, chemoradiation, molecular-targeted therapy, immunotherapy, or any future novel therapies yet to be discovered, whether administered alone or in combination. Specific issues may differ for certain therapies such as immunotherapy, but the grossing process should be similar, and the histologic evaluation should contain these basic elements. Standard pathologic response assessment should allow for comparisons between different therapies and correlations with disease-free survival and overall survival in ongoing and future trials. The International Association for the Study of Lung Cancer has an effort to collect such data from existing and future clinical trials. These recommendations are intended as guidance for clinical trials, although it is hoped they can be viewed as suggestion for good clinical practice outside of clinical trials, to improve consistency of pathologic assessment of treatment response.

The NeST (neoadjuvant systemic therapy in breast cancer) study - Protocol for a prospective multi-centre cohort study to assess the current utilization and short-term outcomes of neoadjuvant systemic therapies in breast cancer

INTRODUCTION

Neoadjuvant systemic therapy (NST) has several potential advantages in the treatment of breast cancer. However, there is currently considerable variation in NST use across the UK. The NeST study is a national, prospective, multicentre cohort study that will investigate current patterns of care with respect to NST in the UK.

METHODS AND ANALYSIS

Phase 1 - a national practice questionnaire (NPQ) to survey current practice.Phase 2 - a multi-centre prospective cohort study of breast cancer patients, undergoing NST.Women undergoing NST as their MDT recommended primary breast cancer treatment between December 2017 and May 2018 will be included. The breast surgery and oncological professional associations and the trainee research collaborative networks will encourage participation by all breast cancer centres.Patient demographics, radiological, oncological, surgical and pathological data will be collected, including complications and the need for further intervention/treatment. Data will be collated to establish current practice in the UK, regarding NST usage and variability of access and provision of these therapies. Prospective data on 600 patients from ~50 centres are anticipated.Trial registration: ISRCTN11160072.

ETHICS AND DISSEMINATION

Research ethics approval is not required for this study, as per the online Health Research Authority decision tool. The information obtained will provide valuable insights to help patients make informed decisions about their treatment. These data should establish current practice in the UK concerning NST, inform future service delivery as well as identifying further research questions.This protocol will be disseminated through the Mammary Fold Academic Research Collaborative (MFAC), the Reconstructive Surgery Trials Network and the Association of Breast Surgery. Participating units will have access to their own data and collective results will be presented at relevant conferences and published in appropriate peer-reviewed journals, as well as being made accessible to relevant patient groups.

Survival Outcomes for Patients With Clinical Complete Response After Neoadjuvant Chemotherapy: Is Omitting Surgery an Option?

BACKGROUND

Surgery after neoadjuvant chemotherapy (NCT) is an accepted treatment approach for locally advanced and some early-stage breast cancers, even for patients with a clinical complete response (cCR) after NCT. This study sought to evaluate the survival outcomes for patients with cCR to NCT who did not undergo surgery.

METHODS

The National Cancer Data Base (NCDB) was used to identify 93,417 women age 18 years or older with a diagnosis of invasive breast cancer who received NCT between 2010 and 2015. The study identified 350 women with cT1-4, N0-3, and M0 tumors who underwent NCT and did not have surgery. A matched surgical cohort was extracted from the NCDB, and overall survival (OS) was compared between the surgical and nonsurgical patients after NCT.

RESULTS

Of the 350 NCT patients who did not undergo surgery, 45 (12.9%) had cCR, 51 (14.6%) had a partial response, 241 (68.9%) had a response but whether complete or partial was not recorded, and 13 (3.7%) had no response/progression. The 5-year OS was better in the cCR group than in the no-cCR group (96.8% vs 69.8%; p = 0.004). A 5-year OS analysis of the cCR patients without surgery (n = 45; median follow-up period, 37 months) compared with the patients with a pathologic complete response who underwent surgery (n = 3938; median follow-up period, 43 months) showed no statistically significant difference (96.8% vs 92.5%, respectively; p = 0.15).

CONCLUSION

This retrospective cohort study demonstrated that active surveillance or de-escalation therapy may be an option for patients who achieve cCR. Prospective studies are underway to determine whether a subgroup of patients may forgo surgery in the setting of cCR after NCT.

Multiparametric MR imaging to assess response following neoadjuvant systemic treatment in various breast cancer subtypes: Comparison between different definitions of pathologic complete response

OBJECTIVES

To validate the performance of multiparametric magnetic resonance (MR) imaging to assess pathologic response to neoadjuvant systemic therapy (NST) in various breast cancer subtypes considering two definitions of pCR: absence of any residual invasive cancer or DCIS (ypT0) and absence of invasive tumour cells (ypT0/is).

METHODS

Institutional review board-approved retrospective study, with waiver of the need to obtain informed consent. From January 2015 to June 2017, 81 women with 82 breast cancers undergoing NST were included. Eighteen lesions (22%) were immunohistochemically HER2-positive, 12 (15%) triple negative (TN), 42 (51%) luminal B-like and 10 (12%) luminal B-like/HER2-positive. Breast MR imaging was performed before and after NST. A comparative analysis considering pCR as ypT0 and ypT0/is was carried out. Performance of univariate and multivariate models to potentially predict pathologic response were evaluated.

RESULTS

ypT0 was attained in 23% (19/82) of cases and ypT0/is in 33% (27/82) of cases. In both scenarios, HER2-positive subtype achieved the best response, 53% and 48%, respectively. A significant relationship was found between late enhancement and pathologic response (p < 0.001) regardless of pCR definition. In the ypT0 scenario, mean ADC ratio in the pCR subgroup was significantly higher than that in the non-pCR subgroup (p = 0.021) but no significant relationship was noted in ypT0/is. A multivariate model including MR late enhancement, ADC ratio and tumor subtype identified pathologic response with 86% and 84% accuracy when ypT0 and ypT0/is were considered, respectively.

CONCLUSION

MR imaging late enhancement and ADC ratio along with breast cancer IHC subtype identify pathologic response following NST with high accuracy, achieving the highest NPV in TN and HER2-positive tumors and the highest PPV in luminal B-like subtypes, regardless of the definition of pCR as ypT0 or ypT0/is. In light of these findings and given that residual DCIS does not have an impact on survival rates, ypT0/is seems to be the preferable definition of pCR.

Accuracy of core biopsy in predicting pathologic complete response in the breast in patients with complete/near complete clinical and radiological response (Complete Responders in the Breast - CRBr) - Trial design and conduct

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Systemic treatments in breast cancer can produce an excellent response.

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Surgery in such patients may only serve the purpose of an excision biopsy.

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Core biopsy of the tumor bed could be a novel technique of identifying responders.

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This protocol studies the accuracy of core biopsies in predicting response.

Introduction

With the advent of taxanes and targeted agents in neoadjuvant chemotherapy (NACT) for breast cancer, the rates of pathologic complete response (pCR) have been steadily increasing. One of the roles of surgery in these women is to serve as a biopsy to confirm or negate a pCR.

Design

This is a prospective validation study. All newly diagnosed non-metastatic breast cancers, of any luminal subtype, planned for neoadjuvant chemotherapy (NACT) with a titanium clip placed in the tumor, will be screened. Eligible patients who have a complete/near complete response to NACT as seen on a mammogram and ultrasound of the breast, will undergo multiple core biopsies of the tumor bed under ultrasound guidance as an outpatient procedure. A minimum of four core biopsy specimens will be mandatory. An MRI will also be done for these patients for documentation and analysis. The core biopsy will be compared to the final histopathology report after definitive surgery.

Objectives

The objective is to study the false negative rate and accuracy of ultrasound guided core biopsies of the tumor bed in predicting pCR. Additionally, the correlation of pCR in the breast with axillary response and the incremental benefit of an MRI in predicting pCR will be evaluated.

Discussion

The concept of using image guided core biopsies to predict pCR could be useful in designing future studies aimed at avoiding redundant surgery in women with a complete response to NACT. This study is registered with Clinical Trials Registry of India (CTRI/2018/01/011122).

Diffusion-weighted imaging of the breast: current status as an imaging biomarker and future role

Diffusion-weighted imaging (DWI) of the breast is a MRI sequence that shows several advantages when compared to the dynamic contrast-enhanced sequence: it does not need intravenous contrast, it is relatively quick and easy to implement (artifacts notwithstanding). In this review, the current applications of DWI for lesion characterization and prognosis as well as for response evaluation are analyzed from the point of view of the necessary steps to become a useful surrogate of underlying biological processes (tissue architecture and cellularity): from the proof of concept, to the proof of mechanism, the proof of principle and finally the proof of effectiveness. Future applications of DWI in screening, DWI modeling and radiomics are also discussed.

Breast conserving therapy after neoadjuvant chemotherapy; data from the Dutch Breast Cancer Audit

INTRODUCTION

NAC has led to an increase in breast conserving surgery (BCS) worldwide. This study aims to analyse trends in the use of neoadjuvant chemotherapy (NAC) and the impact on surgical outcomes.

METHODS

We reviewed all records of cT1-4N0-3M0 breast cancer patients diagnosed between July 2011 and June 2016 who have been registered in the Dutch National Breast Cancer Audit (NBCA) (N = 57.177). The surgical outcomes of 'BCS after NAC' were compared with 'primary BCS', using a multivariable logistic regression model.

RESULTS

Between 2011 and 2016, the use of NAC increased from 9% to 18% and 'BCS after NAC' (N = 4170) increased from 43% to 57%. We observed an involved invasive margin rate (IMR) of 6,7% and a re-excision rate of 6,6%. As compared to 'primary BCS', the IMR of 'BCS after NAC' is higher for cT1 (12,3% versus 8,3%; p < 0.005), equal for cT2 (14% versus 14%; p = 0.046) and lower for cT3 breast cancer (28,3% versus 31%; p < 0.005). Prognostic factors associated with IMR for both 'primary BCS' as for 'BCS after NAC' are: lobular invasive breast cancer and a hormone receptor positive receptor status (all p < 0,005).

CONCLUSION

The use of NAC and the incidence of 'BCS after NAC' increased exponentially in time for all stages of invasive breast cancer in the Netherlands. This nationwide data confirms that 'BCS after NAC' compared to 'primary BCS' leads to equal surgical outcomes for cT2 and improved surgical outcomes for cT3 breast cancer. These promising results encourage current developments towards de-escalation of surgical treatment.

RESPONDER - diagnosis of pathological complete response by vacuum-assisted biopsy after neoadjuvant chemotherapy in breast Cancer - a multicenter, confirmative, one-armed, intra-individually-controlled, open, diagnostic trial

Background

Neoadjuvant chemotherapy (NACT) is a standard approach of the multidisciplinary treatment of breast cancer. Depending on the biological subtype a pathological complete response in the breast (bpCR) can be achieved in up to 60% of the patients. However, only limited accuracy can be reached when using imaging for prediction of bpCR prior to surgery. Due to this diagnostic uncertainty, surgery after NACT is considered to be obligatory for all patients in order to either completely remove residual disease or to diagnose a bpCR histologically. The purpose of this trial is to evaluate the accuracy of a vacuum-assisted biopsy (VAB) to diagnose a bpCR after NACT prior to surgery.

Methods

This study is a multicenter, confirmative, one-armed, intra-individually-controlled, open, diagnostic trial. The study will take place at 21 trial sites in Germany. Six hundred female patients with breast cancer after completed NACT showing at least a partial response to NACT treatment will be enrolled. A vacuum-assisted biopsy (VAB) guided either by ultrasound or mammography will be performed followed by histopathological evaluation of the VAB specimen before standard, guideline-adherent breast surgery. The study is designed to prove that the false negative rate of the VAB is below 10%.

Discussion

As a bpCR is becoming a more frequent result after NACT, the question arises whether breast surgery is therapeutically necessary in such cases. To study this subject further, it will be crucial to develop a reliable test to diagnose a bpCR without surgery.

During the study we anticipate possible problems in patient recruitment as the VAB intervention does not provide participating patients with any personal benefit. Hence, a proficient informed consent discussion with the patient and a detailed explanation of the study aim will be crucial for patient recruitment. Another critical issue is the histopathological VAB evaluation of a non-tumorous specimen as this may have been taken either from the former tumor region (bpCR) or outside of the (former) tumor region (non-representative VAB, sampling error).

Trial registration

The trial has been registered at clinicaltrials.gov with the identifier NCT02948764 on October 28, 2016 and at the German Clinical Trials Register (DRKS00011761) on February 20, 2017. The date of enrolment of the first participant to the trial was on March 8, 2017.

Biopsy Feasibility Trial for Breast Cancer Pathologic Complete Response Detection after Neoadjuvant Chemotherapy: Imaging Assessment and Correlation Endpoints

PURPOSE

This study was designed to present the secondary imaging endpoints of the trial for evaluating mammogram (MMG), ultrasound (US) and image guided biopsy (IGBx) assessment of pathologic complete response (pCR) in breast cancer (BC) patients undergoing neoadjuvant chemotherapy (NAC).

METHODS

Patients with T1-3, N0-3, M0 triple-negative or HER2-positive BC who received NAC were enrolled in an Institutional Review Board-approved prospective, clinical trial. Patients underwent US and MMG at baseline and after NAC. Images were evaluated for residual abnormality and to determine modality for IGBx [US-guided (USG) or stereotactic guided (SG)]. Fine-needle aspiration and 9-G, vacuum-assisted core biopsy (VACBx) of tumor bed was performed after NAC and was compared with histopathology at surgery.

RESULTS

Forty patients were enrolled. Median age was 50.5 (range 26-76) years; median baseline tumor size was 2.4 cm (range 0.8-6.3) and 1 cm (range 0-5.5) after NAC. Nineteen patients had pCR: 6 (32%) had residual Ca²⁺ presurgery, 5 (26%) residual mass, 1 (5%) mass with calcifications, and 7 (37%) no residual imaging abnormality. Sensitivity, specificity, and accuracy of US, MMG, and IGBx for pCR were 47/95/73%, 53/90/73%, and 100/95/98%, respectively. Twenty-five (63%) patients had SGBx and 15 (37%) had US-guided biopsy (USGBx). Median number of cores was higher with SGBx (12, range 6-14) than with USGBx (8, range 4-12), p < 0.002. Positive predictive value for pCR was significantly higher for SG VACBx than for USG VACBx (100 vs. 60%, p < 0.05).

CONCLUSIONS

SG VACBx is the preferred IGBx modality for identifying patients with pCR for trials testing the safety of eliminating surgery.

Meta-analysis of neoadjuvant therapy and its impact in facilitating breast conservation in operable breast cancer

Background

Neoadjuvant therapy (NAT) for operable breast cancer may facilitate more breast-conserving surgery (BCS). It seems, however, that this benefit is not being realized fully.

Methods

A systematic review of the literature was performed. RCTs were included. The criteria for inclusion were: documentation of surgical assessment before and after NAT, surgery performed (BCS or mastectomy), and clinical and pathological responses.

Results

A total of 1452 patients from seven RCTs met the inclusion criteria. After NAT, the feasibility of BCS increased from 43·3 to 60·4 per cent (P &lt; 0·001), but BCS was performed in only 51·8 per cent (P = 0·04). Only 31 per cent of patients who became eligible for BCS (assessed on clinical response) underwent BCS (pooled rate ratio 0·31, 95 per cent c.i. 0·22 to 0·44; P &lt; 0·001). Of the mastectomy candidates who achieved a pathological complete response after NAT, only 41 per cent underwent BCS (pooled rate ratio 0·41, 0·23 to 0·74; P = 0·003). The main factors that influenced the decision not to shift to BCS, even though it was feasible, were clinical assessment before NAT, multicentricity and tumour size at presentation.

Conclusion

Breast surgery performed after NAT does not reflect tumour response, resulting in potentially unnecessary radical surgery, especially mastectomy. The barriers to maximizing the surgical benefits of NAT need to be better understood and explored.

Baseline factors predicting a response to neoadjuvant chemotherapy with implications for non-surgical management of triple-negative breast cancer

BACKGROUND

Patients with triple-negative breast cancer (TNBC) and a pathological complete response (pCR) after neoadjuvant chemotherapy may be suitable for non-surgical management. The goal of this study was to identify baseline clinicopathological variables that are associated with residual disease, and to evaluate the effect of neoadjuvant chemotherapy on both the invasive and ductal carcinoma in situ (DCIS) components in TNBC.

METHODS

Patients with TNBC treated with neoadjuvant chemotherapy followed by surgical resection were identified. Patients with a pCR were compared with those who had residual disease in the breast and/or lymph nodes. Clinicopathological variables were analysed to determine their association with residual disease.

RESULTS

Of the 328 patients, 36·9 per cent had no residual disease and 9·1 per cent had residual DCIS only. Patients with residual disease were more likely to have malignant microcalcifications (P = 0·023) and DCIS on the initial core needle biopsy (CNB) (P = 0·030). Variables independently associated with residual disease included: DCIS on CNB (odds ratio (OR) 2·46; P = 0·022), T2 disease (OR 2·40; P = 0·029), N1 status (OR 2·03; P = 0·030) and low Ki-67 (OR 2·41; P = 0·083). Imaging after neoadjuvant chemotherapy had an accuracy of 71·7 (95 per cent c.i. 66·3 to 76·6) per cent and a negative predictive value of 76·9 (60·7 to 88·9) per cent for identifying residual disease in the breast and lymph nodes. Neoadjuvant chemotherapy did not eradicate the DCIS component in 55 per cent of patients.

CONCLUSION

The presence of microcalcifications on imaging and DCIS on initial CNB are associated with residual disease after neoadjuvant chemotherapy in TNBC. These variables can aid in identifying patients with TNBC suitable for inclusion in trials evaluating non-surgical management after neoadjuvant chemotherapy.

Is Breast Surgery Necessary for Breast Carcinoma in Complete Remission Following Neoadjuvant Chemotherapy?

The likelihood of pathological complete remission (pCR) of breast cancer following neoadjuvant chemotherapy (NACT) is increasing; most of all in the triple negative and HER2 positive tumour subgroups. The question thus arises whether or not breast surgery is necessary when there is complete remission after NACT, and whether it provides any improvement of the oncological treatment result when tumour is no longer detectable. Avoiding surgery and possibly even radiotherapy would only be conceivable on the basis of a reliable diagnosis of pCR without operating. Current imaging does not achieve the necessary sensitivity and specificity to assure the diagnosis of pathological complete remission. Further studies are therefore required to determine which methods are best able to evaluate tumour response to NACT. Studies on image-guided, minimally invasive biopsies after NACT have delivered first promising results towards diagnosing pCR before surgery and could provide the basis for further studies on the possibility of avoiding surgery in this specific patient collective.