Screening Breast MRI Outcomes in Routine Clinical Practice: Comparison to BI-RADS Benchmarks

Auditing Abbreviated Breast MR Imaging: Clinical Considerations and Implications

Abbreviated breast MR (AB-MR) imaging is a relatively new breast imaging tool, which maintains diagnostic accuracy while reducing image times compared with full-protocol breast MR (FP-MR) imaging. Breast imaging audits involve calculating individual and organizational metrics, which can be compared with established benchmarks, providing a standard against which performance can be measured. Unlike FP-MR imaging, there are no established benchmarks for AB-MR imaging but studies demonstrate comparable performance for cancer detection rate, positive predictive value 3, sensitivity, and specificity with T2. We review the basics of performing an audit, including strategies to implement if benchmarks are not being met.

Diagnostic value of synthetic diffusion-weighted imaging on breast magnetic resonance imaging assessment: comparison with conventional diffusion-weighted imaging

PURPOSE

To compare images generated by synthetic diffusion-weighted imaging (sDWI) with those from conventional DWI in terms of their diagnostic performance in detecting breast lesions when performing breast magnetic resonance imaging (MRI).

METHODS

A total of 128 consecutive patients with 135 enhanced lesions who underwent dynamic MRI between 2018 and 2021 were included. The sDWI and DWI signals were compared by three radiologists with at least 10 years of experience in breast radiology.

RESULTS

Of the 82 malignant lesions, 91.5% were hyperintense on sDWI and 73.2% were hyperintense on DWI. Of the 53 benign lesions, 71.7% were isointense on sDWI and 37.7% were isointense on DWI. sDWI provides accurate signal intensity data with statistical significance compared with DWI (P < 0.05). The diagnostic performance of DWI and sDWI to differentiate malignant breast masses from benign masses was as follows: sensitivity 73.1% [95% confidence interval (CI): 62-82], specificity 37.7% (95% CI: 24-52); sensitivity 91.5% (95% CI: 83-96), specificity 71.7% (95% CI: 57-83), respectively. The diagnostic accuracy of DWI and sDWI was 59.2% and 83.7%, respectively. However, when the DWI images were evaluated with apparent diffusion coefficient mapping and compared with the sDWI images, the sensitivity was 92.68% (95% CI: 84-97) and the specificity was 79.25% (95% CI: 65-89) with no statistically significant difference. The inter-reader agreement was almost perfect (P < 0.001).

CONCLUSION

Synthetic DWI is superior to DWI for lesion visibility with no additional acquisition time and should be taken into consideration when conducting breast MRI scans. The evaluation of sDWI in routine MRI reporting will increase diagnostic accuracy.

Outcomes of High-Risk Breast MRI Screening in Women Without Prior History of Breast Cancer: Effectiveness Data from a Tertiary Care Center

OBJECTIVE

To evaluate the diagnostic performance outcomes of a breast MRI screening program in high-risk women without prior history of breast cancer.

METHODS

Retrospective cohort study of 1 405 consecutive screening breast MRI examinations in 681 asymptomatic women with high risk of breast cancer without prior history of breast cancer from January 1, 2015, to December 31, 2019. Outcomes (sensitivity, specificity, positive predictive value, negative predictive value, false-negative rate [FNR], cancer detection rate [CDR]) and characteristics of cancers were determined based on histopathology or 12-month follow-up. MRI examinations performed, BI-RADS assessments, pathology outcomes, and CDRs were analyzed overall and by age decade. Results in incidence screening round (MRI in last 18 months) and nonincidence round were compared.

RESULTS

Breast MRI achieved CDR 20/1000, sensitivity 93.3% (28/30), and specificity 83.4% (1 147/1375). Twenty-eight (28/1 405, CDR 20/1000) screen-detected cancers were identified: 18 (64.3%, 18/28) invasive and 10 (35.7%, 10/28) ductal carcinoma in situ. Overall, 92.9% (26/28) of all cancers were stage 0 or 1 and 89.3% (25/28) were node negative. All 14 incidence screening round malignancies were stage 0 or 1 with N0 disease. Median size for invasive carcinoma was 8.0 mm and for ductal carcinoma in situ was 9.0 mm. There were two false-negative exams for an FNR 0.1% (2/1 405).

CONCLUSION

High-risk screening breast MRI was effective at detecting early breast cancer and associated with favorable outcomes.

Reducing False Negatives in Biopsy of Suspicious MRI Findings

Breast MRI is a highly sensitive imaging modality that often detects findings that are occult on mammography and US. Given the overlap in appearance of benign and malignant lesions, an accurate method of tissue sampling for MRI-detected findings is essential. Although MRI-directed US and correlation with mammography can be helpful for some lesions, a correlate is not always found. MRI-guided biopsy is a safe and effective method of tissue sampling for findings seen only on MRI. The unique limitations of this technique, however, contribute to false negatives, which can result in delays in diagnosis and adverse patient outcomes; this is of particular importance as most MRI examinations are performed in the high-risk or preoperative setting. Here, we review strategies to minimize false negatives in biopsy of suspicious MRI findings, including appropriate selection of biopsy modality, use of meticulous MRI-guided biopsy technique, management after target nonvisualization, assessment of adequate lesion sampling, and determination of radiology-pathology concordance. A proposed management algorithm for MRI-guided biopsy results will also be discussed.

Comparison of the Diagnostic Accuracy of Mammogram-based Deep Learning and Traditional Breast Cancer Risk Models in Patients Who Underwent Supplemental Screening with MRI

Background Access to supplemental screening breast MRI is determined using traditional risk models, which are limited by modest predictive accuracy. Purpose To compare the diagnostic accuracy of a mammogram-based deep learning (DL) risk assessment model to that of traditional breast cancer risk models in patients who underwent supplemental screening with MRI. Materials and Methods This retrospective study included consecutive patients undergoing breast cancer screening MRI from September 2017 to September 2020 at four facilities. Risk was assessed using the Tyrer-Cuzick (TC) and National Cancer Institute Breast Cancer Risk Assessment Tool (BCRAT) 5-year and lifetime models as well as a DL 5-year model that generated a risk score based on the most recent screening mammogram. A risk score of 1.67% or higher defined increased risk for traditional 5-year models, a risk score of 20% or higher defined high risk for traditional lifetime models, and absolute scores of 2.3 or higher and 6.6 or higher defined increased and high risk, respectively, for the DL model. Model accuracy metrics including cancer detection rate (CDR) and positive predictive values (PPVs) (PPV of abnormal findings at screening [PPV1], PPV of biopsies recommended [PPV2], and PPV of biopsies performed [PPV3]) were compared using logistic regression models. Results This study included 2168 women who underwent 4247 high-risk screening MRI examinations (median age, 54 years [IQR, 48-60 years]). CDR (per 1000 examinations) was higher in patients at high risk according to the DL model (20.6 [95% CI: 11.8, 35.6]) than according to the TC (6.0 [95% CI: 2.9, 12.3]; P < .01) and BCRAT (6.8 [95% CI: 2.9, 15.8]; P = .04) lifetime models. PPV1, PPV2, and PPV3 were higher in patients identified as high risk by the DL model (PPV1, 14.6%; PPV2, 32.4%; PPV3, 36.4%) than those identified as high risk with the TC (PPV1, 5.0%; PPV2, 12.7%; PPV3, 13.5%; P value range, .02-.03) and BCRAT (PPV1, 5.5%; PPV2, 11.1%; PPV3, 12.5%; P value range, .02-.05) lifetime models. Conclusion Patients identified as high risk by a mammogram-based DL risk assessment model showed higher CDR at breast screening MRI than patients identified as high risk with traditional risk models. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Bae in this issue.

Elastography Assisted BI-RADS in the Preoperative Breast Magnetic Resonance Imaging 4a Lesions in China

OBJECTIVES

A considerable number of benign lesions, especially category 4a lesions on Breast Imaging Reporting and Data System Magnetic Resonance Imaging (BI-RADS-MRI), were biopsied according to BI-RADS-MRI, which was a diagnostic imaging challenge. This study aimed to evaluate the diagnostic performance of ultrasound elastography (UE) assisted Breast Imaging Reporting and Data System (BI-RADS) for BI-RADS-MRI category 4a lesions.

METHODS

Between January 2017 and December 2019, 228 breast lesions categorized as BI-RADS-MRI 4a were included. Conventional ultrasound (US) and UE were performed to evaluate each lesion. Pathology results were used as the gold standard. The diagnostic performances of different UE methods and our re-assessment proposal were evaluated.

RESULTS

When BI-RADS-MRI category 4a, BI-RADS-US category 3-4a, the stiffness of soft or intermediate in elasticity assessment according to the fifth edition of the BI-RADS atlas, strain ratio < 1.335, age ≤ 52 years, and the maximum diameter of lesion ≤20 mm were simultaneously met, an ultrasound-guided empty needle biopsy was not recommended, but short-term ultrasound follow-up for 3-6 months was recommended, and biopsy was performed after changes in evaluation. In this way, 95 of 228 BI-RADS-MRI category 4a lesions avoided biopsies, and the number of patients with biopsies decreased by 41.7%.

CONCLUSIONS

UE offers benefits in the characterization of BI-RADS-MRI category 4a lesions. Ultrasound and elastography can help optimize therapy recommendations for BI-RADS-MRI category 4a lesions by our re-assessment proposal.

Breast MRI: an illustration of benign findings

Despite its unparalleled sensitivity for aggressive breast cancer, breast MRI continually excites criticism for a specificity that lags behind that of modern mammographic techniques. Radiologists reporting breast MRI need to recognise the range of benign appearances on breast MRI to avoid unnecessary biopsy. This review summarises the reported diagnostic accuracy of breast MRI with particular attention to the technique's specificity, provides a referenced reporting strategy and discusses factors that compromise diagnostic confidence. We then present a pictorial review of benign findings on breast MRI. Enhancing radiological skills to discriminate malignant from benign findings will minimise false positive biopsies, enabling optimal use of multiparametric breast MRI for the benefit of screening clients and breast cancer patients.

Muscle mass loss in breast cancer patients of reproductive age (≤ 45 years) undergoing neoadjuvant chemotherapy

PURPOSE

Loss of muscle mass is associated with negative clinical outcome in breast cancer (BC) patients. Therefore, the aim of the study is to evaluate if there is pectoralis muscle area (PMA) depletion, reflecting loss of muscle mass, in breast cancer patients of reproductive age (≤ 45 years) undergoing neoadjuvant chemotherapy (NAC) and to correlate PMA with clinical and histopathological data.

MATERIAL AND METHODS

This monocentric study, approved by our institutional review board, enrolled a total of 52 consecutive patients (mean age 37 ± 4.96 years) with histologically proven primary breast cancer between January 2019 and September 2021, treated with NAC and in whom tumor response and PMA were assessed with breast MRI. Two radiologists calculated PMA before and after NAC independently and blindly on axial 3D FLASH pre-contrast T1-weighted images. Wilcoxon-Mann-Whitney U test compared median values and percentage changes of pectoralis muscle area at the beginning and at the end of NAC (158 ± 25.5 days). Multivariate regression analysis on ΔPMA (difference between PMA pre-NAC and PMA post-NAC) was done according to clinical and histopathological data. Inter-reader and intra-reader agreement was estimated with K statistics.

RESULTS

Pre-NAC PMA mean value was larger than post-NAC PMA mean value (9.6 ± 2.6 cm² vs. 8.7 ± 2.2 cm², p < 0.001, delta value 1.41). According to the RECIST criteria, no significant differences between complete and partial response were found. Multivariate regression analysis did not show any significant relationships between ΔPMA and age, time between MRI examinations, estrogen and progesterone receptor status, human epidermal growth factor receptor 2 status, Ki-67 expression, lymph node involvement, RECIST criteria, histological type, and different regimes of NAC. Inter-reader (k = 0.74) and intra-reader agreement (0.67 and 0.73) in PMA assessment was good.

CONCLUSIONS

PMA variation in BC young patients, directly estimated on breast MRI, could be a potential tool to monitor body composition during NAC with potential implications in improving outcome.

Screening MRI in Women at Intermediate Breast Cancer Risk: An Update of the Recent Literature

Guidelines issued by the American Cancer Society (ACS) in 2007 recommend neither for nor against screening MRI in women at intermediate breast cancer risk (15%–20%), including those with dense breast tissue, a history of lobular neoplasia or atypical ductal hyperplasia (ADH), or a prior breast cancer, because of scarce supporting evidence about the utility of MRI in these specific patient populations. However, since the issuance of the ACS guidelines in 2007, multiple investigations have found that women at intermediate risk may be suitable candidates for screening MRI, given the high detection rates of early-stage cancers and acceptable false-positive rates. For women with dense breast tissue, the Dense Tissue and Early Breast Neoplasm Screening trial reported that the incremental cancer detection rate (CDR) by MRI exceeded 16 cancers per 1000 examinations but decreased in the second round of screening; this decrease in CDR, however, occurred alongside a marked decrease in the false-positive rate. For women with lobular neoplasia or ADH, single-institution retrospective analyses have shown CDRs mostly ranging from 11 to 16 cancers per 1000 MRI examinations, with women with lobular carcinoma in situ benefitting more than women with atypical lobular hyperplasia or ADH. For patients with a prior breast cancer, the cancer yield by MRI varies widely but mostly ranges from 8 to 20 cancers per 1000 examinations, with certain subpopulations more likely to benefit, such as those with dense breasts. This article reviews and summarizes more recent studies on MRI screening of intermediate-risk women.

Opportunities in cancer imaging: risk-adapted breast imaging in screening

In the UK, women between 50-70 years are invited for 3-yearly mammography screening irrespective of their likelihood of developing breast cancer. The only risk adaption is for women with >30% lifetime risk who are offered annual magnetic resonance imaging (MRI) and mammography, and annual mammography for some moderate-risk women. Using questionnaires, breast density, and polygenic risk scores, it is possible to stratify the population into the lowest 20% risk, who will develop <4% of cancers and the top 4%, who will develop 18% of cancers. Mammography is a good screening test but has low sensitivity of 60% in the 9% of women with the highest category of breast density (BIRADS D) who have a 2.5- to fourfold breast cancer risk. There is evidence that adding ultrasound to the screening mammogram can increase the cancer detection rate and reduce advanced stage interval and next round cancers. Similarly, alternative tests such as contrast-enhanced mammography (CESM) or abbreviated MRI (ABB-MRI) are much more effective in detecting cancer in women with dense breasts. Scintimammography has been shown to be a viable alternative for dense breasts or for follow-up in those with a personal history of breast cancer and scarring as result of treatment. For supplemental screening to be worthwhile in these women, new technologies need to reduce the number of stage II cancers and be cost effective when tested in large scale trials. This article reviews the evidence for supplemental imaging and examines whether a risk-stratified approach is feasible.

Magnetic Resonance Imaging in Screening of Breast Cancer

Magnetic Resonance (MR) imaging is the most sensitive modality for breast cancer detection but is currently limited to screening women at high risk due to limited specificity and test accessibility. However, specificity of MR imaging improves with successive rounds of screening, and abbreviated approaches have the potential to increase access and decrease cost. There is growing evidence to support supplemental MR imaging in moderate-risk women, and current guidelines continue to evolve. Functional imaging has the potential to maximize survival benefit of screening. Leveraging MR imaging as a possible primary screening tool is therefore also being investigated in average-risk women.

Breast Magnetic Resonance Imaging Audit: Pitfalls, Challenges, and Future Considerations

Breast magnetic resonance (MR) imaging is the most sensitive imaging modality for breast cancer detection and guidelines recommend its use, in addition to screening mammography, for high-risk women. The most recent American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) manual coordinated cross-modality BI-RADS terminology and established an outcome monitoring section that helps guide a medical imaging outcomes audit. This article provides a framework for performing a breast MR imaging audit in clinical practice, incorporating ACR BI-RADS guidance and more recently published data, clarifies common pitfalls, and discusses audit challenges related to evolving clinical practice.

Development and Implementation of an Algorithm to Guide MRI Screening in Patients With a Personal History of Treated Breast Cancer

INTRODUCTION

Limited data exist to guide appropriate use of magnetic resonance imaging (MRI) screening in women with a personal history of breast cancer. We developed an algorithm to inform the use of MRI screening in patients with a personal history, implemented it, and evaluated initial implementation at our community and academic practice sites.

PATIENTS AND METHODS

A multidisciplinary committee of providers developed the initial algorithm on the basis of available literature and consensus. To evaluate projected MRI utilization based on the initial algorithm and inform algorithm revision, charts of patients < 80 years of age diagnosed and treated in 2010 with stage 0-III breast cancer (n = 236) were reviewed. The revised algorithm was implemented into the electronic medical record (September 2013). Thirteen months after implementation (2014-2015), chart review of patients with a personal history of breast cancer who underwent screening MRI was performed to assess algorithm adherence.

RESULTS

Before algorithm development, 9% (20/236) of patients received MRI screening (6 genetic mutation/family history, 4 occult primary, 8 young age/breast density, 2 unknown). Use of MRI screening was projected to increase to 25% with algorithm implementation. In postimplementation review, we identified 183 patients with a personal history of breast cancer who underwent screening MRI, with 94% algorithm adherence.

CONCLUSION

We successfully developed and implemented an algorithm to guide MRI screening in patients with a personal breast cancer history. Clinicians can use this algorithm to guide patient discussions regarding the utility of MRI screening. Further prospective study, including cancer detection rates, biopsy rate, and mortality, are necessary to confirm the algorithm's usefulness.

Supplemental Screening for Patients at Intermediate and High Risk for Breast Cancer

The sensitivity of mammography is more limited in patients with dense breasts and some patients at higher risk for breast cancer. Patients with intermediate or high risk for breast cancer may begin screening earlier and benefit from supplemental screening techniques beyond standard 2-dimensional mammography. A patient's individual risk factors for developing breast cancer, their breast density, and the evidence supporting specific modalities for a given clinical scenario help to determine the need for supplemental screening and the modality chosen. Additional factors include the availability of supplemental screening techniques at an individual institution, cost, insurance coverage, and state-specific breast density legislation.

Availability Versus Utilization of Supplemental Breast Cancer Screening Post Passage of Breast Density Legislation

Objective: Despite the lack of evidence that supplemental screening in women with dense breasts reduces breast cancer mortality, 38 states have passed breast density legislation, with some including recommendations for supplemental screening. The objective of this study is to compare the availability versus use of supplemental breast cancer screening modalities and determine factors driving use of supplemental screening in rural versus urban settings. Methods: A 50-item mailed survey using the Tailored Design Method was sent to American College of Radiology mammography-accredited facilities in North Carolina in 2017. Respondents included 94 facilities (48 rural and 46 urban locations). Survey questions focused on breast cancer and supplemental screening services, breast density, risk factors/assessment, and facility demographics. Results: The survey response rate was 60.3% (94/156). Among the 94 respondents, 64.0% (n = 60) reported availability of any type of supplemental screening (digital breast tomosynthesis [DBT], ultrasound, or magnetic resonance imaging [MRI]). In facilities where supplemental screening modalities were available, the most commonly utilized supplemental screening modality was DBT (96.4%), compared with ultrasound (35.7%) and MRI (46.7%). Facilities reported using supplemental screening based on patient breast density (48.3%), referring physician recommendation (63.3%), reading radiologist recommendation (63.3%), breast cancer risk factors (48.3%), and patient request (40.0%). Urban facilities were more likely than rural facilities to base supplemental screening on breast cancer risk factors (62.5% vs. 32.1%; p-value = 0.019), referring physician (75.0% vs. 50.0%; p-value = 0.045), and reading radiologist (78.1% vs. 46.4%; p-value = 0.011). Conclusion: In our study, supplemental screening modalities were widely available, with facilities more likely to use DBT for supplemental screening compared to other modalities.

Abbreviated Screening Breast MRI in Women at Higher-than-Average Risk for Breast Cancer with Prior Normal Full Protocol MRI

OBJECTIVE

To compare the performance of abbreviated screening breast MRI (ABMR) versus full protocol MRI (FPMR) in women at higher-than-average risk for breast cancer with a prior normal FPMR.

METHODS

ABMR was performed on higher-than-average-risk women who had a prior normal FPMR. ABMR protocol consisted of short inversion time inversion recovery imaging, precontrast, and two early postcontrast sequences acquired in under 10 minutes. Retrospective review of ABMR examinations performed from July 2016 to July 2018 was compared with a control group who underwent routine screening with FPMR who had a prior normal FPMR performed from July 2014 to June 2016. Screening outcome metrics were calculated and compared, adjusting for differences in patient demographics.

RESULTS

The study cohort included 481 ABMR examinations, while the control group included 440 FPMR studies. There was no significant difference in the abnormal interpretation rate (AIR) or cancer detection rate (CDR) for the ABMR versus the FPMR group (AIR 6.0% vs 6.8% respectively, odds ratio (OR) 0.91, 95% confidence interval (CI): 0.53-1.5, P = 0.73; CDR 8.3 vs 11 cancers detected per 1000 examinations respectively, OR 0.73, 95% CI: 0.20-2.7, P = 0.64). The PPV2 and PPV3 for the ABMR group was 19% and 21% versus 16% and 16% for the FPMR group, with no statistical difference. Sensitivity was 100% in each group with no interval cancers. There was no difference in specificity between the ABMR and FPMR groups, 93% versus 94%, respectively (P = 0.73).

CONCLUSION

ABMR may be used to screen higher-than-average-risk women with a prior normal FPMR as outcome metrics are equivalent to FPMR.

Diffusion-weighted MRI at 3.0 T for detection of occult disease in the contralateral breast in women with newly diagnosed breast cancer

PURPOSE

Diffusion-weighted magnetic resonance imaging (DW-MRI) offers unenhanced method to detect breast cancer without cost and safety concerns associated with dynamic contrast-enhanced (DCE) MRI. Our purpose was to evaluate the performance of DW-MRI at 3.0T in detection of clinically and mammographically occult contralateral breast cancer in patients with unilateral breast cancer.

METHODS

Between 2017 and 2018, 1130 patients (mean age 53.3 years; range 26-84 years) with newly diagnosed unilateral breast cancer who underwent breast MRI and had no abnormalities on clinical and mammographic examinations of contralateral breast were included. Three experienced radiologists independently reviewed DW-MRI (b = 0 and 1000 s/mm²) and DCE-MRI and assigned a BI-RADS category. Using histopathology or 1-year clinical follow-up, performance measures of DW-MRI were compared with DCE-MRI.

RESULTS

A total of 21 (1.9%, 21/1130) cancers were identified (12 ductal carcinoma in situ and 9 invasive ductal carcinoma; mean invasive tumor size, 8.0 mm) in the contralateral breast. Cancer detection rate of DW-MRI was 13-15 with mean of 14 per 1000 examinations (95% confidence interval [CI] 9-23 per 1000 examinations), which was lower than that of DCE-MRI (18-19 with mean of 18 per 1000 examinations, P = 0.01). A lower abnormal interpretation rate (14.0% versus 17.0%, respectively, P < 0.001) with higher specificity (87.3% versus 84.6%, respectively, P < 0.001) but lower sensitivity (77.8% versus 96.8%, respectively, P < 0.001) was noted for DW-MRI compared to DCE-MRI.

CONCLUSIONS

DW-MRI at 3.0T has the potential as a cost-effective tool for evaluation of contralateral breast in women with newly diagnosed breast cancer.

Screening in patients with increased risk of breast cancer (part 1): pros and cons of MRI screening

Screening plays an important role in women with a high risk of breast cancer. Given this population's high incidence of breast cancer and younger age of onset compared to the general population, it is recommended that screening starts earlier. There is ample evidence that magnetic resonance imaging (MRI) is the most sensitive diagnostic tool, and American and the European guidelines both recommend annual MRI screening (with supplementary annual mammography) as the optimum screening modality. Nevertheless, the current guidelines do not totally agree about the recommendations for MRI screening in some subgroups of patients. The first part of this article on screening in women with increased risk of breast cancer reviews the literature to explain and evaluate the advantages of MRI screening compared to screening with mammography alone: increased detection of smaller cancers with less associated lymph node involvement and a reduction in the rate of interval cancers, which can have an impact on survival and mortality (with comparable effects to other preventative measures). At the same time, however, we would like to reflect on the drawbacks of MRI screening that affect its applicability.

Muscle mass loss after neoadjuvant chemotherapy in breast cancer: estimation on breast magnetic resonance imaging using pectoralis muscle area

OBJECTIVES

The loss of skeletal muscle mass is widely considered a predictor of poor survival and toxicity in breast cancer patients. The aim of this study is to evaluate if there is pectoralis muscle area (PMA) variation, reflecting loss of skeletal muscle mass, on consecutive MRI examinations after neoadjuvant chemotherapy.

METHODS

The retrospective study protocol was approved by our institutional review board. A total of n = 110 consecutive patients (mean age 56 ± 11 years) who were treated with neoadjuvant chemotherapy (NAC) for histologically proven primary breast cancer between January 2017 and January 2019 and in whom tumor response was checked with standard breast MRI were included. Two radiologists calculated the pectoralis muscle cross-sectional area before and after NAC.

RESULTS

Time between the MRI examinations, before starting NAC and after completing NAC, was 166.8 ± 50 days. PMA calculated pre-NAC (8.14 cm²) was larger than PMA calculated post-NAC (7.03 cm²) (p < 0.001). According to the Response Evaluation Criteria in Solid Tumors (RECIST) criteria, there were no significant differences between responders (complete or partial response) and non-responders (p = 0.362). The multivariate regression analysis did not show any significant relationships between ΔPMA and age, time between MRI exams, estrogen and progesterone receptor status, human epidermal growth factor receptor status (HER-2), Ki-67 expression, lymph node status, RECIST criteria, histological type, average lesion size, molecular categories, and grade. Inter-reader (k = 0.72) and intra-reader agreement (0.69 and 0.71) in PMA assessment were good.

CONCLUSIONS

Pectoralis muscle mass varies in breast cancer patients undergoing NAC and this difference can be estimated directly on standard breast MRI.

KEY POINTS

• Pectoralis muscle area variation reflects loss of skeletal muscle mass. • Pectoralis muscle area on MRI is reduced after NAC. • Pectoralis muscle mass loss seems independent from other variables.

The Effect of Prior Comparison MRI on Interpretive Performance of Screening Breast MRI

OBJECTIVE

To evaluate the effect of prior comparison MRI on interpretive performance of screening breast MRI.

METHODS

After institutional review board approval, all screening breast MRI examinations performed from January 2011 through December 2014 were retrospectively reviewed. Screening performance metrics were estimated and compared for exams with and without a prior comparison MRI, using logistic regression models to adjust for age and screening indication (BRCA mutation or thoracic radiation versus breast cancer history versus high-risk lesion history versus breast cancer family history).

RESULTS

Most exams, 4509 (87%), had a prior comparison MRI (incidence round), while 661 (13%) did not (prevalence round). Abnormal interpretation rate (6% vs 20%, P < 0.01), biopsy rate (3% vs 9%, P < 0.01), and false-positive biopsy recommendation rate per 1000 exams (21 vs 71, P < 0.01) were significantly lower in the incidence rounds compared to the prevalence rounds, while specificity was significantly higher (95% vs 81%, P < 0.01). There was no difference in cancer detection rate (CDR) per 1000 exams (12 vs 20, P = 0.1), positive predictive value of biopsies performed (PPV3) (35% vs 23%, P = 0.1), or sensitivity (86% vs 76%, P = 0.4).

CONCLUSION

Presence of a prior comparison significantly improves incidence round screening breast MRI examination performance compared with prevalence round screening. Consideration should be given to updating the BI-RADS breast MRI screening benchmarks and auditing prevalence and incidence round examinations separately.

Diffusion tensor imaging for characterizing tumor microstructure and improving diagnostic performance on breast MRI: a prospective observational study

Background

Diffusion-weighted imaging (DWI) can increase breast MRI diagnostic specificity due to the tendency of malignancies to restrict diffusion. Diffusion tensor imaging (DTI) provides further information over conventional DWI regarding diffusion directionality and anisotropy. Our study evaluates DTI features of suspicious breast lesions detected on MRI to determine the added diagnostic value of DTI for breast imaging.

Methods

With IRB approval, we prospectively enrolled patients over a 3-year period who had suspicious (BI-RADS category 4 or 5) MRI-detected breast lesions with histopathological results. Patients underwent multiparametric 3 T MRI with dynamic contrast-enhanced (DCE) and DTI sequences. Clinical factors (age, menopausal status, breast density, clinical indication, background parenchymal enhancement) and DCE-MRI lesion parameters (size, type, presence of washout, BI-RADS category) were recorded prospectively by interpreting radiologists. DTI parameters (apparent diffusion coefficient [ADC], fractional anisotropy [FA], axial diffusivity [λ₁], radial diffusivity [(λ₂ + λ₃)/2], and empirical difference [λ₁ − λ₃]) were measured retrospectively. Generalized estimating equations (GEE) and least absolute shrinkage and selection operator (LASSO) methods were used for univariate and multivariate logistic regression, respectively. Diagnostic performance was internally validated using the area under the curve (AUC) with bootstrap adjustment.

Results

The study included 238 suspicious breast lesions (95 malignant, 143 benign) in 194 women. In univariate analysis, lower ADC, axial diffusivity, and radial diffusivity were associated with malignancy (OR = 0.37–0.42 per 1-SD increase, p < 0.001 for each), as was higher FA (OR = 1.45, p = 0.007). In multivariate analysis, LASSO selected only ADC (OR = 0.41) as a predictor for a DTI-only model, while both ADC (OR = 0.41) and FA (OR = 0.88) were selected for a model combining clinical and imaging parameters. Post-hoc analysis revealed varying association of FA with malignancy depending on the lesion type. The combined model (AUC = 0.81) had a significantly better performance than Clinical/DCE-MRI-only (AUC = 0.76, p < 0.001) and DTI-only (AUC = 0.75, p = 0.002) models.

Conclusions

DTI significantly improves diagnostic performance in multivariate modeling. ADC is the most important diffusion parameter for distinguishing benign and malignant breast lesions, while anisotropy measures may help further characterize tumor microstructure and microenvironment.

Contrast-enhanced MRI for breast cancer screening

Multiple studies in the first decade of the 21^st century have established contrast-enhanced breast MRI as a screening modality for women with a hereditary or familial increased risk for the development of breast cancer. In recent studies, in women with various risk profiles, the sensitivity ranges between 81% and 100%, which is approximately twice as high as the sensitivity of mammography. The specificity increases in follow-up rounds to around 97%, with positive predictive values for biopsy in the same range as for mammography. MRI preferentially detects the more aggressive/invasive types of breast cancer, but has a higher sensitivity than mammography for any type of cancer. This performance implies that in women screened with breast MRI, all other examinations must be regarded as supplemental. Mammography may yield ~5% additional cancers, mostly ductal carcinoma in situ, while slightly decreasing specificity and increasing the costs. Ultrasound has no supplemental value when MRI is used. Evidence is mounting that in other groups of women the performance of MRI is likewise superior to more conventional screening techniques. Particularly in women with a personal history of breast cancer, the gain seems to be high, but also in women with a biopsy history of lobular carcinoma in situ and even women at average risk, similar results are reported. Initial outcome studies show that breast MRI detects cancer earlier, which induces a stage-shift increasing the survival benefit of screening. Cost-effectiveness is still an issue, particularly for women at lower risk. Since costs of the MRI scan itself are a driving factor, efforts to reduce these costs are essential. The use of abbreviated MRI protocols may enable more widespread use of breast MRI for screening. Level of Evidence: 1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;50:377-390.

Utility of Diffusion-weighted Imaging to Decrease Unnecessary Biopsies Prompted by Breast MRI: A Trial of the ECOG-ACRIN Cancer Research Group (A6702)

PURPOSE

Conventional breast MRI is highly sensitive for cancer detection but prompts some false positives. We performed a prospective, multicenter study to determine whether apparent diffusion coefficients (ADCs) from diffusion-weighted imaging (DWI) can decrease MRI false positives.Experimental Design: A total of 107 women with MRI-detected BI-RADS 3, 4, or 5 lesions were enrolled from March 2014 to April 2015. ADCs were measured both centrally and at participating sites. ROC analysis was employed to assess diagnostic performance of centrally measured ADCs and identify optimal ADC thresholds to reduce unnecessary biopsies. Lesion reference standard was based on either definitive biopsy result or at least 337 days of follow-up after the initial MRI procedure.

RESULTS

Of 107 women enrolled, 67 patients (median age 49, range 24-75 years) with 81 lesions with confirmed reference standard (28 malignant, 53 benign) and evaluable DWI were analyzed. Sixty-seven of 81 lesions were BI-RADS 4 (n = 63) or 5 (n = 4) and recommended for biopsy. Malignancies exhibited lower mean in centrally measured ADCs (mm²/s) than benign lesions [1.21 × 10^-3 vs.1.47 × 10^-3; P < 0.0001; area under ROC curve = 0.75; 95% confidence interval (CI) 0.65-0.84]. In centralized analysis, application of an ADC threshold (1.53 × 10^-3 mm²/s) lowered the biopsy rate by 20.9% (14/67; 95% CI, 11.2%-31.2%) without affecting sensitivity. Application of a more conservative threshold (1.68 × 10^-3 mm²/s) to site-measured ADCs reduced the biopsy rate by 26.2% (16/61) but missed three cancers.

CONCLUSIONS

DWI can reclassify a substantial fraction of suspicious breast MRI findings as benign and thereby decrease unnecessary biopsies. ADC thresholds identified in this trial should be validated in future phase III studies.

American College of Radiology Accreditation, Performance Metrics, Reimbursement, and Economic Considerations in Breast MR Imaging

Accreditation through the American College of Radiology (ACR) Breast Magnetic Resonance Imaging Accreditation Program is necessary to qualify for reimbursement from Medicare and many private insurers and provides facilities with peer review on image acquisition and clinical quality. Adherence to ACR quality control and technical practice parameter guidelines for breast MR imaging and performance of a medical outcomes audit program will maintain high-quality imaging and facilitate accreditation. Economic factors likely to influence the practice of breast MR imaging include cost-effectiveness, competition with lower-cost breast-imaging modalities, and price transparency, all of which may lower the cost of MR imaging and allow for greater utilization.

Utility of BI-RADS Assessment Category 4 Subdivisions for Screening Breast MRI

OBJECTIVE

BI-RADS for mammography and ultrasound subdivides category 4 assessments by likelihood of malignancy into categories 4A (> 2% to ≤ 10%), 4B (> 10% to ≤ 50%), and 4C (> 50% to < 95%). Category 4 is not subdivided for breast MRI because of a paucity of data. The purpose of the present study is to determine the utility of categories 4A, 4B, and 4C for MRI by calculating their positive predictive values (PPVs) and comparing them with BI-RADS-specified rates of malignancy for mammography and ultrasound.

MATERIALS AND METHODS

All screening breast MRI examinations performed from July 1, 2010, through June 30, 2013, were included in this study. We identified in medical records prospectively assigned MRI BI-RADS categories, including category 4 subdivisions, which are used routinely in our practice. Benign versus malignant outcomes were determined by pathologic analysis, findings from 12 months or more clinical or imaging follow-up, or a combination of these methods. Distribution of BI-RADS categories and positive predictive value level 2 (PPV2; based on recommendation for tissue diagnosis) for categories 4 (including its subdivisions) and 5 were calculated.

RESULTS

Of 860 screening breast MRI examinations performed for 566 women (mean age, 47 years), 82 with a BI-RADS category 4 assessment were identified. A total of 18 malignancies were found among 84 category 4 and 5 assessments, for an overall PPV2 of 21.4% (18/84). For category 4 subdivisions, PPV2s were as follows: for category 4A, 2.5% (1/40); for category 4B, 27.6% (8/29); for category 4C, 83.3% (5/6); and for category 4 (not otherwise specified), 28.6% (2/7).

CONCLUSION

Category 4 subdivisions for MRI yielded malignancy rates within BI-RADS-specified ranges, supporting their use for benefits to patient care and more meaningful practice audits.