_{Published October 12, 2022}

Contrast-enhanced mammography (CEM) is a relatively new modality which is rapidly gaining acceptance in breast imaging. Many medical centers have already acquired the necessary equipment to implement CEM programs [1], thus creating an ever-increasing demand for trusted CEM educational resources.

At the same time, however, there remains a paucity of quality instructional materials for this emerging tool, a lack of structured, case-based training, and fundamental misconceptions regarding both the technical aspects and the operational/administrative knowledge needed for successful implementation of CEM.

On day one of the 2023 ARRS Annual Meeting, Sunday, April 16, live (and virtually, of course) from Honolulu on the enchanting island of Oahu, HI, Drs. Wendie Berg, Bhavika Patel, and I, will offer a two-hour introductory program on practical CEM for radiologists. Our Featured Sunday Session, “Contrast-Enhanced Mammography: The Essentials and Beyond,” will include interactive didactic and case-based lectures to educate and update practicing radiologists on the important foundational principles of CEM. The course will be supplemented with an optional short pre- and post-test survey to help the audience organize the information and evaluate their learning progress.

CEM Augments Mammography Capabilities in the Digital Era

The strength of CEM is its ability to provide both morphologic information on low-energy images, similar to a standard 2D mammogram, and functional information of contrast distribution on the “recombined” (subtracted and processed) images. This is achieved by software and hardware modifications to modern mammographic equipment and necessitates patient workflow adjustments in breast centers [2]. The course will present the basics of CEM technology, its strengths and limitations, as well as helpful tips on implementing this modality in clinical practice.  

Additionally, the course will serve as a guide to CEM image interpretation with a special emphasis on utilization of the newly introduced Breast Imaging Reporting & Data System (BI-RADS®) CEM lexicon [3].

We will also discuss background parenchymal enhancement (BPE) in CEM image interpretation. Similar to breast tissue density of mammography, increased BPE may both mask and mimic cancer on CEM. As on MRI, there are four categories of BPE (Fig. 1), and multiple factors are associated with increased BPE [4]. We will present the audience with a range of appearances for normal BPE on CEM.

Drs. Berg, Patel, and myself will provide a case-based introduction to the most common artifacts and cancer mimics on CEM, too. This topic is continuously evolving. In the July issue of AJR, enhancing cherry hemangioma has been described as a common benign finding that may be misleading (Fig. 2) [5]. It is helpful for the technologist to make note of skin lesions, which can be marked to facilitate recognition.

CEM Screening and Diagnostic Applications

Chief among the topics discussed will be the role of CEM, alongside other legacy modalities, in today’s screening and diagnostic guidelines and society-endorsed consensus recommendations for breast cancer imaging. CEM is already recommended as an alternative to MRI in screening of women at high risk of breast cancer and in average-risk women with dense breasts [6]. An AJR article from 2021 demonstrated that CEM shows promise as a breast cancer screening examination in patients with a personal history of lobular neoplasia [7].  

Of clinical importance is the fact that enhancing CEM-detected lesions that have an ultrasound correlate are more likely to be malignant. These data were also published by AJR in 2021 [8]. Among 153 enhancing lesions detected on CEM in 144 patients, the authors found ultrasound correlates in 47 (31%). Furthermore, this means that a substantial number of enhancing findings can potentially be sampled with ultrasound-guided biopsy (Fig. 3).

Diagnostic applications of CEM in breast imaging continue to evolve. In the July issue of AJR, CEM was compared with MRI for neoadjuvant therapy (NAT) response assessment [9, 10]. After NAT for breast cancer, CEM and MRI yielded similar assessments of lesion size (both slightly overestimated vs. pathology) and RECIST categories, and no significant difference in specificity for complete pathologic response. Duly noting that MRI had higher sensitivity for complete pathologic response, Bernardi et al. showed preliminary data suggesting that a delayed CEM acquisition 6 minutes after contrast injection could help detect residual ductal carcinoma in situ (DCIS) [10]. The authors concluded that while MRI remains the preferred test for NAT monitoring, the findings support CEM as a useful alternative when MRI is contraindicated or not tolerated [10, 11].

CEM may be a useful alternative to MRI in women with newly diagnosed breast cancer and breast augmentation. The findings of Carnahan et al. published in AJR last year suggest the plausibility of CEM for disease extent assessment in women with breast augmentation and contraindication or limited access to MRI [12].

 The study evaluated 17 female breast cancer patients with breast implant augmentation, who underwent both CEM and MRI for staging. CEM and MRI were concordant for the index cancer in all 17 women. Six additional lesions were demonstrated by CEM and confirmed by MRI in 6 (35%) women: three multifocal, one multicentric, and two contralateral; two (33%) were malignant (one each invasive ductal and invasive lobular carcinoma). MRI did not identify any additional cancers not seen on CEM.

CEM-Guided Biopsy

Perhaps the largest unmet need for expertly curated CEM education surrounds CEM-guided biopsy. Case in point: recently FDA-approved—but not yet widely available—direct CEM-guided biopsy is often a necessary step in patient management. In the absence of CEM-guided biopsy capability, suspicious enhancing findings that have no definite correlate on low energy images, tomosynthesis, or ultrasound require possible MRI-guided biopsy for diagnosis. This increases cost and prolongs diagnostic workup. With the introduction of CEM-guided biopsy technology, this workflow is expected to become more streamlined and efficient.  Our subspecialized presenters have personal experience with this technology and will deliver a comprehensive overview of the current state of knowledge and the future directions of CEM-guided biopsies.   

CEM Essentials—and Beyond—at the ARRS Annual Meeting

Contemporary breast imagers must become more familiar with the range of indications and contraindications on CEM, such as normal variants, BPE, pathology, and artifacts. Focused sessions will also address interpretative skills in CEM—including appropriate use of the recently released BI-RADS CEM lexicon from the American College of Radiology—giving radiologists in private and academic practices alike applied insights from real-life cases.

Although the target audience for our course is predominantly medical imaging professionals considering or actively implementing CEM in practice, the curriculum presented live on Sunday, April 16 will also be relevant and valuable for recent residency or fellowship graduates, particularly those transitioning to imaging practices with established CEM services.

As the field moves forward, medical centers with established CEM programs will inevitably need to educate an incoming imaging workforce and new trainees who have not experienced enough clinical exposure to this modality in their previous practices or training programs. Apropos, “Contrast-Enhanced Mammography: The Essentials and Beyond” will also offer participants a unique opportunity to test and evaluate a newly developed online teaching module for CEM, purposefully designed to train the radiologists of today and tomorrow in clinical implementation of CEM in their own practices.

References

1. Gandhi J, Phillips J. Contrast-Enhanced Mammography: Current Applications and Future Directions. ARRS InPractice website. ARRSInPractice.org/contrast-enhanced-mammography-current-applications-and-future-directions. Published March 1, 2022. Accessed September 12, 2022
2. Perry H, Phillips J, Dialani V, Slanetz PJ, Fein-Zachary VJ, Karimova EJ, et al. Contrast-Enhanced Mammography: A Systematic Guide to Interpretation and Reporting. AJR 2019; 212:222–223
3. Breast Imaging Reporting & Data System (BI-RADS®) Contrast Enhanced Mammography (CEM) Supplement. ACR website. http://www.acr.org/-/media/ACR/Files/RADS/BI-RADS/BIRADS_CEM_2022.pdf. Published 2022. Accessed September 12, 2022
4. Karimi Z, Phillips J, Slanetz P, Lotfi P, Dialani V, Karimova J, et al. Factors Associated With Background Parenchymal Enhancement on Contrast-Enhanced Mammography. AJR 2020; 216:340–348
5. Lu AH, Zuley ML, Berg WA. Enhancing Cherry Hemangioma: A Mimic for Breast Cancer on Contrast-Enhanced Mammography. American Journal of Roentgenology. 2022;219(1):160-1.
6. The ACR Appropriateness Criteria® American College of Radiology Appropriateness Criteria. Supplemental Breast Cancer Screening Based on Breast Density. ACR website. acsearch.acr.org/docs/3158166/Narrative. Published 2021. Accessed September 12, 2022.
7. Hogan MP, Amir T, Sevilimedu V, Sung J, Morris EA, Jochelson MS. Contrast-Enhanced Digital Mammography Screening for Intermediate-Risk Women With a History of Lobular Neoplasia. AJR 2021; 216:1486–1491
8. Coffey K, Sung J, Comstock C, Askin G, Jochelson MS, Morris EA, et al. Utility of Targeted Ultrasound to Predict Malignancy Among Lesions Detected on Contrast-Enhanced Digital Mammography. AJR 2021; 217:595–604
9. Woodard S. Editorial comment: evidence supporting contrast-enhanced mammography (CEM) for monitoring neoadjuvant chemotherapy response and showing the potential of delayed CEM. AJR 2022;11
10. Bernardi D. et al. Contrast-enhanced mammography versus MRI in the evaluation of neoadjuvant therapy response in patients with breast cancer: a prospective study. AJR 2022; 14:1–11
11. Alabousi M. Role of Contrast-Enhanced Mammography in Breast Cancer Neoadjuvant Therapy Response. AJR podcast website. AJRpodcast.libsyn.com/role-of-contrast-enhanced-mammography-in-breast-cancer-neoadjuvant-therapy-response. Published August 10, 2022. Accessed September 12, 2022
12. Carnahan MB et al. Contrast-enhanced mammography for newly diagnosed breast cancer in women with breast augmentation: preliminary findings. AJR 2021; 217:855–856