Interval Cancers in Understanding Screening Outcomes.

Interval breast cancers are not detected at routine screening and are diagnosed in the interval between screening examinations. A variety of factors contribute to interval cancers, including patient and tumor characteristics as well as the screening technique and frequency. The interval cancer rate is an important metric by which the effectiveness of screening may be assessed and may serve as a surrogate for mortality benefit.

18F-FDG Dedicated Breast PET Complementary to Breast MRI for Evaluating Early Response to Neoadjuvant Chemotherapy.

Purpose To compare quantitative measures of tumor metabolism and perfusion using fluorine 18 (18F) fluorodeoxyglucose (FDG) dedicated breast PET (dbPET) and breast dynamic contrast-enhanced (DCE) MRI during early treatment with neoadjuvant chemotherapy (NAC). Materials and Methods Prospectively collected DCE MRI and 18F-FDG dbPET examinations were analyzed at baseline (T0) and after 3 weeks (T1) of NAC in 20 participants with 22 invasive breast cancers. FDG dbPET-derived standardized uptake value (SUV), metabolic tumor volume, and total lesion glycolysis (TLG) and MRI-derived percent enhancement (PE), signal enhancement ratio (SER), and functional tumor volume (FTV) were calculated at both time points. Differences between FDG dbPET and MRI parameters were evaluated after stratifying by receptor status, Ki-67 index, and residual cancer burden. Parameters were compared using Wilcoxon signed rank and Mann-Whitney U tests. Results High Ki-67 tumors had higher baseline SUVmean (difference, 5.1; P = .01) and SUVpeak (difference, 5.5; P = .04). At T1, decreases were observed in FDG dbPET measures (pseudo-median difference T0 minus T1 value [95% CI]) of SUVmax (-6.2 [-10.2, -2.6]; P < .001), SUVmean (-2.6 [-4.9, -1.3]; P < .001), SUVpeak (-4.2 [-6.9, -2.3]; P < .001), and TLG (-29.1 mL3 [-71.4, -6.8]; P = .005) and MRI measures of SERpeak (-1.0 [-1.3, -0.2]; P = .02) and FTV (-11.6 mL3 [-22.2, -1.7]; P = .009). Relative to nonresponsive tumors, responsive tumors showed a difference (95% CI) in percent change in SUVmax of -34.3% (-55.9%, 1.5%; P = .06) and in PEpeak of -42.4% (95% CI: -110.5%, 8.5%; P = .08). Conclusion 18F-FDG dbPET was sensitive to early changes during NAC and provided complementary information to DCE MRI that may be useful for treatment response evaluation. Keywords: Breast, PET, Dynamic Contrast-enhanced MRI Clinical trial registration no. NCT01042379 Supplemental material is available for this article. © RSNA, 2024.

MRI of the Lactating Breast.

The breasts undergo marked physiologic changes during lactation that can make conventional imaging evaluation with mammography and US challenging. MRI can be a valuable diagnostic aid to differentiate physiologic and benign processes from malignancy in patients who are lactating. In addition, MRI may allow more accurate delineation of disease involvement than does conventional imaging and assists in locoregional staging, screening of the contralateral breast, assessment of response to neoadjuvant chemotherapy, and surgical planning. Although the American College of Radiology recommends against patients undergoing contrast-enhanced MRI during pregnancy because of fetal safety concerns, contrast-enhanced MRI is safe during lactation. As more women delay childbearing, the incidence of pregnancy-associated breast cancer (PABC) and breast cancer in lactating women beyond the 1st year after pregnancy is increasing. Thus, MRI is increasingly being performed in lactating women for diagnostic evaluation and screening of patients at high risk. PABC is associated with a worse prognosis than that of non-PABCs, with delays in diagnosis contributing to an increased likelihood of advanced-stage disease at diagnosis. Familiarity with the MRI features of the lactating breast and the appearance of various pathologic conditions is essential to avoid diagnostic pitfalls and prevent delays in cancer diagnosis and treatment. The authors review clinical indications for breast MRI during lactation, describe characteristic features of the lactating breast at MRI, and compare MRI features of a spectrum of benign and malignant breast abnormalities. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Chikarmane in this issue.

Prevalent vs Incident Screen: Why Does It Matter?

There are important differences in the performance and outcomes of breast cancer screening in the prevalent compared to the incident screening rounds. The prevalent screen is the first screening examination using a particular imaging technique and identifies pre-existing, undiagnosed cancers in the population. The incident screen is any subsequent screening examination using that technique. It is expected to identify fewer cancers than the prevalent screen because it captures only those cancers that have become detectable since the prior screening examination. The higher cancer detection rate at prevalent relative to incident screening should be taken into account when analyzing the medical audit and effectiveness of new screening technologies.

The role of digital mammographic surveillance for detection of asymptomatic recurrence in autologous flap reconstructions.

OBJECTIVE: To evaluate the utility of digital mammography in detecting asymptomatic malignancy in autologous flap reconstructions after mastectomy. METHODS: A retrospective database review identified all mammograms performed on asymptomatic patients with flap reconstructions over a 9-year period (1/1/2009 to 12/31/2017). A negative examination was defined as BI-RADS 1 or 2 and a positive examination was defined as BI-RADS 0, 4, or 5 assigned to the mastectomy side. Malignant outcomes were determined by pathology results. Interval cancers, or false negatives, were defined as locoregional malignant diagnosis within one year of a negative mammogram. Sensitivity, specificity, predictive values, abnormal interpretation rate, and cancer detection rate were calculated. RESULTS: 626 mammograms of asymptomatic flap reconstructions were performed in 183 patients. The most common flap type was TRAM (83.5 %, 523/626) and DIEP (13.4 %, 84/626). Most exams (98.2 %, 615/626) were negative, assessed as BI-RADS 1 or 2, with no interval cancers at follow-up. Eleven exams (1.8 %, 11/626) were positive, assessed as BI-RADS 0, 4, or 5. After diagnostic work-up of all BI-RADS 0 exams, 9 cases had a final recommendation for biopsy of which 3 were malignant. Mammography yielded a cancer detection rate of 0.5 % (3/626), abnormal interpretation rate of 1.8 % (11/626), NPV of 100 % (615/615), overall PPV of 27.3 % (3/11), PPV2 (positive predictive value of a biopsy recommendation) of 33.3 % (3/9), sensitivity of 100 % (3/3), and specificity of 98.7 % (615/623). CONCLUSION: Digital mammography of asymptomatic autologous flap reconstructions after mastectomy demonstrated high sensitivity and low abnormal interpretation rate. Cancer detection rate was comparable to current national benchmarks for mammographic screening in the general U.S. population without mastectomy.

Deep Learning to Simulate Contrast-enhanced Breast MRI of Invasive Breast Cancer.

Background There is increasing interest in noncontrast breast MRI alternatives for tumor visualization to increase the accessibility of breast MRI. Purpose To evaluate the feasibility and accuracy of generating simulated contrast-enhanced T1-weighted breast MRI scans from precontrast MRI sequences in biopsy-proven invasive breast cancer with use of deep learning. Materials and Methods Women with invasive breast cancer and a contrast-enhanced breast MRI examination that was performed for initial evaluation of the extent of disease between January 2015 and December 2019 at a single academic institution were retrospectively identified. A three-dimensional, fully convolutional deep neural network simulated contrast-enhanced T1-weighted breast MRI scans from five precontrast sequences (T1-weighted non-fat-suppressed [FS], T1-weighted FS, T2-weighted FS, apparent diffusion coefficient, and diffusion-weighted imaging). For qualitative assessment, four breast radiologists (with 3-15 years of experience) blinded to whether the method of contrast was real or simulated assessed image quality (excellent, acceptable, good, poor, or unacceptable), presence of tumor enhancement, and maximum index mass size by using 22 pairs of real and simulated contrast-enhanced MRI scans. Quantitative comparison was performed using whole-breast similarity and error metrics and Dice coefficient analysis of enhancing tumor overlap. Results Ninety-six MRI examinations in 96 women (mean age, 52 years ± 12 [SD]) were evaluated. The readers assessed all simulated MRI scans as having the appearance of a real MRI scan with tumor enhancement. Index mass sizes on real and simulated MRI scans demonstrated good to excellent agreement (intraclass correlation coefficient, 0.73-0.86; P < .001) without significant differences (mean differences, -0.8 to 0.8 mm; P = .36-.80). Almost all simulated MRI scans (84 of 88 [95%]) were considered of diagnostic quality (ratings of excellent, acceptable, or good). Quantitative analysis demonstrated strong similarity (structural similarity index, 0.88 ± 0.05), low voxel-wise error (symmetric mean absolute percent error, 3.26%), and Dice coefficient of enhancing tumor overlap of 0.75 ± 0.25. Conclusion It is feasible to generate simulated contrast-enhanced breast MRI scans with use of deep learning. Simulated and real contrast-enhanced MRI scans demonstrated comparable tumor sizes, areas of tumor enhancement, and image quality without significant qualitative or quantitative differences. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Slanetz in this issue. An earlier incorrect version appeared online. This article was corrected on January 17, 2023.

Symmetric activation and modulation of the human calcium-sensing receptor.

The human extracellular calcium-sensing (CaS) receptor controls plasma Ca2+ levels and contributes to nutrient-dependent maintenance and metabolism of diverse organs. Allosteric modulation of the CaS receptor corrects disorders of calcium homeostasis. Here, we report the cryogenic-electron microscopy reconstructions of a near-full-length CaS receptor in the absence and presence of allosteric modulators. Activation of the homodimeric CaS receptor requires a break in the transmembrane 6 (TM6) helix of each subunit, which facilitates the formation of a TM6-mediated homodimer interface and expansion of homodimer interactions. This transformation in TM6 occurs without a positive allosteric modulator. Two modulators with opposite functional roles bind to overlapping sites within the transmembrane domain through common interactions, acting to stabilize distinct rotamer conformations of key residues on the TM6 helix. The positive modulator reinforces TM6 distortion and maximizes subunit contact to enhance receptor activity, while the negative modulator strengthens an intact TM6 to dampen receptor function. In both active and inactive states, the receptor displays symmetrical transmembrane conformations that are consistent with its homodimeric assembly.

Intermediary clip placement to assist accurate axillary lymph node localization.

Localization of metastatic axillary lymph nodes in breast cancer patients is an increasingly common procedure performed by radiologists. In 2014, the National Comprehensive Cancer Network guidelines stated that "clinically positive axillary lymph node (s) should be sampled by FNA or core biopsy and clipped with image-detectable marker; clipped lymph nodes must be removed if FNA or core biopsy was positive prior to neoadjuvant therapy". Since then, multiple studies have further supported targeted axillary surgery after neoadjuvant chemotherapy (NAC), with excision of the clipped metastatic axillary node in addition to the sentinel node (s). Requests for image guided localization of clipped axillary nodes will continue to increase and likely become the standard of care. However, when lymph nodes have decreased in size after NAC, or when small deep lymph nodes are sampled, the clipped node can be difficult to identify under ultrasound at the time of localization. When the target node is questionable, we have found it valuable to place an intermediary clip, and use an axillary mammographic view to confirm this intermediary clip co-localizes with the intended target. With this confirmation, safe, accurate localization can then be performed. We describe 3 cases of intermediary clip placement facilitating successful localization of previously clipped axillary lymph nodes.

The Value of Targeted Ultrasound for the Primary Evaluation of Breast Symptoms in Pregnant Women of All Ages.

OBJECTIVE: Data on breast imaging in symptomatic pregnant women are limited. Our aim was to assess the value of targeted breast US for the primary evaluation of breast symptoms in pregnant women of all ages. METHODS: This IRB-approved retrospective study included all pregnant patients who underwent targeted US for focal breast symptoms at an academic imaging facility over an 18-year period (2000-2018). Clinical, imaging, and pathology results were reviewed. Malignant outcomes were determined by histology. Benign outcomes were confirmed by pathology or ≥2 years of follow-up. Descriptive statistics and 2 × 2 contingency table analyses were performed at the presentation level. RESULTS: The study cohort comprised 178 presentations in 175 pregnant women. Mean age was 34.7 years (standard deviation, 5.2). The majority (153/178, 86.0%) were more than 30 years old. At presentation, 42.1% (75/178) were in the first trimester of pregnancy, 27.0% (48/178) in the second, and 29.8% (53/178) in the third. The most common presenting symptom was a palpable lump (162/178, 91.0%), followed by focal pain (7/178, 3.9%). The vast majority (174/178, 97.8%) of cases were non-malignant. However, targeted US detected all 4 malignancies (cancer detection rate, 22/1000; negative predictive value 136/136, 100%). Sensitivity and specificity were 100% (4/4) and 78.2% (136/174), respectively. CONCLUSION: Benign causes of symptoms in pregnant women were far more common; malignancy was rare, accounting for only 2.2% (4/178) of cases. Targeted breast US detected all malignancies, supporting US as the primary imaging modality for evaluating symptomatic pregnant women, regardless of age.

US as the Primary Imaging Modality in the Evaluation of Palpable Breast Masses in Breastfeeding Women, Including Those of Advanced Maternal Age.

Background Women are increasingly delaying childbearing, and thus lactation, into their 30s and 40s, when mammography would typically be the initial imaging modality to evaluate palpable masses in the general population. Current guidelines recommend US as the first-line imaging modality for palpable masses in pregnant and lactating women, but data regarding breastfeeding women age 30 years and older are near nonexistent. Purpose To evaluate the diagnostic performance of targeted US as the primary imaging modality for the evaluation of palpable masses in lactating women, including those of advanced maternal age. Materials and Methods Lactating women with palpable breast masses evaluated at targeted US over a 17-year period (January 2000 to July 2017) were retrospectively identified. All US evaluations were performed at diagnostic evaluation, and mammography was performed at the discretion of the interpreting radiologist. Breast Imaging Reporting and Data System assessments, imaging, and pathology results were collected. Descriptive statistics and 2 × 2 contingency tables were assessed at the patient level. Results There were 167 women (mean age, 35 years ± 5 [standard deviation]), 101 of whom (60%) were of advanced maternal age (≥35 years). All women underwent targeted US, and 98 (59%) underwent mammography in addition to US. The frequency of malignancy was five of 167 (3.0%). Targeted US demonstrated a sensitivity and specificity of five of five (100%; 95% confidence interval [CI]: 48%, 100%) and 114 of 162 (70%; 95% CI: 63%, 77%), respectively. Negative predictive value, positive predictive value of an abnormal examination, and positive predictive value of biopsy were 114 of 114 (100%; 95% CI: 97%, 100%), five of 53 (9.4%; 95% CI: 3%, 21%), and five of 50 (10%; 95% CI: 3%, 22%), respectively. In the subset of 98 women who underwent mammography in addition to US, mammography depicted seven incidental suspicious findings, which lowered the specificity from 62 of 93 (67%; 95% CI: 56%, 76%) to 57 of 93 (61%; 95% CI: 51%, 71%) (P = .02). Conclusion Targeted US depicted all malignancies in lactating women with palpable masses. Adding mammography increased false-positive findings without any additional cancer diagnoses. © RSNA, 2020 See also the editorial by Newell in this issue.

Author Correction: Structure of human GABAB receptor in an inactive state.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Primum non nocere: Utility and outcomes of pediatric breast ultrasound.

PURPOSE: To assess the use and outcomes of ultrasound for the evaluation of breast signs and symptoms in pediatric females. METHODS: A retrospective database review identified all patients ≤18-years-old who underwent breast ultrasound at an academic institution over a 20-year period. Each symptomatic site was designated a case and analyses were performed on each case. Imaging findings were obtained from the radiology reports. Clinical and pathology data were obtained from the medical records. Descriptive statistics were performed. RESULTS: The final cohort comprised 124 cases in 101 patients. Mean age was 15 years (range 1-18). The most common indication for ultrasound was a palpable lump (71%). Thirty-seven cases (30%) demonstrated no sonographic correlate to the symptom; 36 (29%) had a benign correlate. The most common benign correlates were abscess/phlegmon and cyst. All cases of abscess/phlegmon had infectious symptoms. Fifty-one cases (41%) demonstrated a sonographic mass that was not characteristically benign. Of these indeterminate masses, 27 were recommended for biopsy, 13 for short-interval follow-up, and 6 had no recommendation. Of 27 biopsied masses, 63% were fibroadenomas. No symptoms were due to malignancy. Therefore, the NPV of ultrasound was 100% and the PPV 0%. CONCLUSION: In this cohort of pediatric and adolescent patients, malignancy was never the cause of breast symptoms. Imaging yielded false positives with a biopsy recommendation in 22% of cases. Ultrasound provided value in evaluating infectious symptoms. Given the extreme rarity of breast cancer in this population, surveillance may be a safe alternative for most indeterminate lesions.

Structure of human GABAB receptor in an inactive state.

The human GABAB receptor-a member of the class C family of G-protein-coupled receptors (GPCRs)-mediates inhibitory neurotransmission and has been implicated in epilepsy, pain and addiction1. A unique GPCR that is known to require heterodimerization for function2-6, the GABAB receptor has two subunits, GABAB1 and GABAB2, that are structurally homologous but perform distinct and complementary functions. GABAB1 recognizes orthosteric ligands7,8, while GABAB2 couples with G proteins9-14. Each subunit is characterized by an extracellular Venus flytrap (VFT) module, a descending peptide linker, a seven-helix transmembrane domain and a cytoplasmic tail15. Although the VFT heterodimer structure has been resolved16, the structure of the full-length receptor and its transmembrane signalling mechanism remain unknown. Here we present a near full-length structure of the GABAB receptor, captured in an inactive state by cryo-electron microscopy. Our structure reveals several ligands that preassociate with the receptor, including two large endogenous phospholipids that are embedded within the transmembrane domains to maintain receptor integrity and modulate receptor function. We also identify a previously unknown heterodimer interface between transmembrane helices 3 and 5 of both subunits, which serves as a signature of the inactive conformation. A unique 'intersubunit latch' within this transmembrane interface maintains the inactive state, and its disruption leads to constitutive receptor activity.

Performance of screening MRI in high risk patients at initial versus subsequent screen.

PURPOSE: To compare the characteristics, outcomes, and performance metrics in women undergoing initial breast MRI screening versus subsequent screening. METHODS: A retrospective database search identified screening MRIs performed at an academic practice from 2013 to 2015. MRIs were divided into two groups: (1) initial screens and (2) subsequent screens (interpreted with at least one prior MRI for comparison). Benignity was confirmed with pathology or >1-year follow-up. Malignancy was confirmed by pathology. Performance metrics were calculated. Comparisons were made using Binomial and Fisher's exact tests. RESULTS: We observed a higher rate of abnormal interpretations (52% vs. 19%; p < 0.001) and rate of biopsy (49% vs. 15%; p < 0.001) in the initial versus subsequent screen group. The positive predictive value of biopsy was slightly lower at initial versus subsequent screen (17% vs. 19%, p = 0.99). However, the cancer detection rate was higher at initial than at subsequent screen (85 vs. 29/1000, p = 0.08). Sensitivity was higher at initial (100%) versus subsequent (88%) screen. However, the specificity at initial screen was low (55%) compared to subsequent screen (83%). CONCLUSIONS: The higher rate of abnormal interpretations in the initial versus subsequent screen group in part reflects a prevalence screening. Although we observed more abnormal interpretations in the initial screen, this was likely justified by the significantly higher cancer detection. This evidence may be used to counsel patients and referring providers on the expected higher likelihood of recall from an initial screening MRI balanced with higher detection of malignancies. Findings also highlight the importance of having comparison MRIs to decrease false positives.

Digital Breast Tomosynthesis: Technique and Common Artifacts.

Image optimization at digital breast tomosynthesis (DBT) involves a series of trade-offs between multiple variables. Wider sweep angles provide better separation of overlapping tissues, but they result in decreased in-plane resolution as well as increased scan times that may be prone to patient motion. Techniques to reduce scan time, such as continuous tube motion and pixel binning during detector readout, reduce the chances of patient motion but may degrade the in-plane resolution. Image artifacts are inherent to DBT because of the limited angular range of the acquisition. Iterative reconstruction algorithms have been shown to reduce various DBT artifacts.

Initial experience of dedicated breast PET imaging of ER+ breast cancers using [F-18]fluoroestradiol.

Dedicated breast positron emission tomography (dbPET) is an emerging technology with high sensitivity and spatial resolution that enables detection of sub-centimeter lesions and depiction of intratumoral heterogeneity. In this study, we report our initial experience with dbPET using [F-18]fluoroestradiol (FES) in assessing ER+ primary breast cancers. Six patients with >90% ER+ and HER2- breast cancers were imaged with dbPET and breast MRI. Two patients had ILC, three had IDC, and one had an unknown primary tumor. One ILC patient was treated with letrozole, and another patient with IDC was treated with neoadjuvant chemotherapy without endocrine treatment. In this small cohort, we observed FES uptake in ER+ primary breast tumors with specificity to ER demonstrated in a case with tamoxifen blockade. FES uptake in ILC had a diffused pattern compared to the distinct circumscribed pattern in IDC. In evaluating treatment response, the reduction of SUVmax was observed with residual disease in an ILC patient treated with letrozole, and an IDC patient treated with chemotherapy. Future study is critical to understand the change in FES SUVmax after endocrine therapy and to consider other tracer uptake metrics with SUVmax to describe ER-rich breast cancer. Limitations include variations of FES uptake in different ER+ breast cancer diseases and exclusion of posterior tissues and axillary regions. However, FES-dbPET has a high potential for clinical utility, especially in measuring response to neoadjuvant endocrine treatment. Further development to improve the field of view and studies with a larger cohort of ER+ breast cancer patients are warranted.

Characterization of Metastatic Sternal Lesions on Dynamic Contrast-Enhanced Breast MRI in Women with Invasive Breast Cancer.

RATIONALE AND OBJECTIVES: Detecting sternal lesions is not the purpose of breast MRI, but diagnosing metastasis has major clinical implications. Our purpose was to determine the breast MRI features of sternal metastases detected on PET-CT and bone-scan. MATERIALS AND METHODS: Between 01/2010-09/2018, 379 patients with breast cancer had sternal findings on PET-CT or bone-scan, 21 of which underwent breast MRI within 100 days. Sternal lesions were considered metastatic if (1) biopsy demonstrated metastasis, (2) the lesion had similar appearance to synchronous sites of biopsy-proven osseous metastases, or (3) there were numerous suspicious lesions in which widespread osseous metastasis was presumed. Four radiologists reviewed the MR images to determine if metastases were retrospectively detectable. MRI reports were reviewed to determine if lesions were prospectively described. MRI features of metastatic sternal lesions were compared to benign controls. RESULTS: Fourteen sternal metastases met inclusion criteria. Lesions were retrospectively detectable on breast MRI by all radiologists in 86% (12/14) of cases, but prospectively reported in 57%. Of the 12 MRI-detectable metastases, mean maximum dimension was 33 mm, 7 had >1 lesion, all were T1-hypointense, 11 were T2-hyperintense, 11 were noncircumscribed, 6 extended beyond cortex, 11 enhanced heterogeneously, and 11 demonstrated washout. Heterogeneous enhancement (p = 0.002), noncircumscribed margins (p < 0.001), multiplicity (p = 0.005), and size >1 cm (p < 0.001) were more frequent with metastatic compared to benign sternal lesions. CONCLUSION: Most sternal metastases (86%) were retrospectively detectable on breast MRI, but only 57% were prospectively reported, emphasizing the importance evaluating the sternum on breast MRI. Certain MRI features may raise suspicion for metastasis.

Complete Breast MRI Response to Neoadjuvant Chemotherapy and Prediction of Pathologic Complete Response.

OBJECTIVE: To assess the negative predictive value (NPV) of breast MRI in detecting residual disease after neoadjuvant chemotherapy (NAC) in women with invasive breast cancer, overall and by tumor subtype. METHODS: An institutional review board approved retrospective study from January 2010 through December 2016 identified patients with invasive breast cancer who achieved complete MRI response to NAC, defined as the absence of residual enhancement in the tumor bed above background parenchymal enhancement. During the study period, it was our routine practice to assign a BI-RADS 1 or 2 assessment to these cases. The NPV was defined as the ability of a complete MRI response to predict pathologic complete response (pCR) at final surgical pathology. Statistical analyses were performed using a Fisher exact test. RESULTS: Among 244 patients who underwent MRI to assess NAC response, 38 (16%) were determined to have complete MRI response by the interpreting radiologist. Of these, 20/38 (53%) had pCR. Complete MRI response did not significantly predict pCR for the total group (P < 0.9). However, NPVs significantly varied by molecular subtype (P < 0.004). True negative MRIs by tumor subtype were 2/10 (20%) for hormone receptor (HR)+/HER2-, 3/10 (30%) for HR+/HER2+, 6/8 (75%) for HR-/HER+, and 9/10 (90%) for triple negative (TN) subtypes. Complete MRI response significantly predicted pCR for only the TN subtype (NPV 90%; P < 0.02). CONCLUSIONS: In patients with complete MRI response, 53% had pCR. While MRI lacks sufficient NPV to obviate the need for surgical excision, it may add prognostic value for certain molecular subtypes. The TN subtype demonstrated the highest NPV.