Impact of the New Jersey Breast Density Law on Imaging and Intervention Volumes and Breast Cancer Diagnosis.

Sanders LM1, King AB2, Goodman KS3.
  • 1Breast Center, Barnabas Health Ambulatory Care Center, Livingston, New Jersey; Rutgers New Jersey Medical School, Newark, New Jersey. Electronic address:
  • 2Breast Center, Barnabas Health Ambulatory Care Center, Livingston, New Jersey.
  • 3Department of Surgery, Saint Barnabas Medical Center, Livingston, New Jersey.




Increased breast density is acknowledged as an independent risk factor for breast cancer and may obscure malignancy on mammography. Approximately half of all mammograms depict dense breasts. Legislation related to mandatory breast density notification was first enacted in Connecticut in 2009. On May 1, 2014, New Jersey joined other states with similar legislation. The New Jersey breast density law (NJBDL) mandates that mammography reports acknowledge the relevance and masking effect of mammographic breast density. The aim of this study was to assess the impact of the NJBDL at one of the state’s largest ACR-accredited breast centers.


A retrospective chart review was performed to determine changes in imaging and intervention utilization and modality of cancer diagnosis after enactment of the legislation. Data for the present study were extracted from a review of all patients with core biopsy-proven malignancy at a large outpatient breast center between November 1, 2012, and October 31, 2015. Data were divided into the 18-month period before the implementation of the NJBDL (November 1, 2012 to April 30, 2014) and the 18-month period after passage of the law (May 1, 2014 to October 31, 2015).


Screening ultrasound increased significantly after the implementation of the NJBDL, by 651% (1,530 vs 11,486). MRI utilization increased by 59.3% (2,595 vs 4,134). A total of 1,213 cancers were included in the final analysis, 592 in the first time period and 621 after law implementation. Breast cancer was most commonly detected on screening mammography, followed by diagnostic mammography with ultrasound for palpable concern, in both time periods. Of the 621 cancers analyzed, 26.1% (n = 162) were found in patients 50 years of age or younger. Results demonstrated that with respect to how malignancies were detected, age and average mammographic density were both statistically significant (P = .002).


The NJBDL succeeded in publicizing the masking effect of dense breasts. The number of supplemental screening ultrasound and MRI examinations increased after the implementation of this legislation. An efficacy analysis affirmed the high sensitivity of screening MRI compared with other modalities. The use of MRI increased core biopsy efficiency and reduced the number of biopsies needed per cancer diagnosed.


Breast; MRI; breast cancerdensityimaging; risk; screening

PMID: 27318582; DOI:10.1016/j.jacr.2016.05.005



The relative amounts of fat and fibroglandular tissue   determine how dense breasts appear on mammograms.  Fat is radiolucent, or dark, whereas fibroglandular tissue is radiodense and appears white on these x-ray studies.   Women with more relatively more fibroglandular tissue and less fat have denser breasts, which may obscure developing  breast malignancies.    In 2009, Connecticut became the first state to enact a breast density law; there are currently 28 states that have passed similar legislation.  The general purpose of these state laws is to acknowledge the masking effect of increased mammographic density on breast cancer detection.   Federal law in 1992 mandates that patients who undergo mammography receive direct notification of their results in a “lay letter.”    The New Jersey law, which took effect May 1, 2014, specified that lay letters contain specific verbiage advising that patients engage with their health providers on the subject of  breast density, and discuss their need for supplemental screening tests, such as tomosynthesis (an add-on component of mammography), ultrasound or MRI.  The NJ law also mandated insurance coverage for those supplemental exams. 

At the Breast Center of the Ambulatory Care Center of RWJBarnabas Health, in Livingston, NJ, one of the largest centers of breast imaging and intervention in the state, we undertook a retrospective analysis to determine the effects of the law.  We investigated changes in utilization of imaging modalities and the downstream effect on the number of breast biopsies and breast cancers diagnosed by each modality.  We analyzed those patients diagnosed with breast cancer with respect to their age, mammographic breast density and lifetime risk.   Data from two time periods were compared: 18 months prior to and 18 months following the law’s  implementation (1).   

Data showed that although the screening mammography volumes remained flat (decreasing from approximately 59,000   to 56,000 exams), screening ultrasound studies increased seven fold and total MRIs increased by a factor of 1.6.     Overall, total breast core biopsies performed by stereotactic, ultrasound and MRI guidance dropped.  Based on results of the ACRIN 6666 trial, we expected the increased utilization of screening ultrasound to quadruple our ultrasound core biopsy rate, however, it only rose by less than 4%.    These results were attributed to the increased use of breast MRI.  Non-enhancement of sonographically indeterminate or suspicious lesions (BI-RADS 4) on breast MRI has been shown to be 100% accurate in excluding malignancy (2).   Breast MRI was recommended in patients with multiple indeterminate lesions on ultrasound to evaluate enhancement, in an effort to decrease the false negative core biopsy rate. 

 A greater number of cancers were diagnosed following the law’s implementation despite a reduction in total core biopsies.   Excluding cancers detected on diagnostic imaging studies for breast symptoms or referred for biopsy based on outside imaging, screening  mammogram detected the most cancers.   Supplemental screening ultrasound and MRI studies accounted for 47 of the 284 cancers foundby screening, or 16.5%.   Analysis of the efficacy of each modality showed that screening ultrasound detected the fewest cancers per 1,000 women screened, screening mammography detected twice as many,  and MRI detected three times as many cancers per 1000 women screened as mammography.  Diagnostic MRI detected the most cancers per 1000 women imaged. 

Approximately a third of patients who were initially imaged at our institution were diagnosed with cancer because of a palpable concern and approximately one fourth of cancers were diagnosed in patients 50 years of age or younger.    

A comparison of the patients diagnosed by each of the three screening modalities was made with respect to three variables: age of diagnosis, density of mammogram and lifetime risk.  Patients whose cancers were diagnosed by screening mammogram and ultrasound were significantly older  compared to those diagnosed by screening MRI .  Patients whose cancers were diagnosed by mammography had significantly less dense breasts than those who were diagnosed by ultrasound or MRI, attributable to the following facts:  1) mammography performs better as a test to find cancer in less dense breasts, and 2) supplemental screening modalities were more frequently utilized in women with negative but dense mammograms.   The lifetime risks of the women diagnosed with cancer by each screening modality category were averaged; the three pooled averages were all found to be under 15%.   This confirms widely known data that approximately 75-90% of women diagnosed with breast cancer are not “high risk “(defined as lifetime risk over 20%).

These data support the following conclusions of this study.

1.  The determination to perform supplemental breast imaging studies should be based on mammographic density regardless of risk.   16.5% of cancers diagnosed were found by supplemental screening studies in denser breasts.    

2.  MRI was the most efficient modality to diagnose breast cancer.   Its increased use resulted in fewer core biopsies performed per cancer diagnosed.   However, patients and referring doctors still experienced considerable difficulty in obtaining authorizations for MRI exams.   

3.  Considering that over a quarter of diagnosed cancers were in women 50 or under, we reject the United States Preventive Services Task Force recommendations of every other year mammography in women over 50.   40% of life years lost to breast cancer are in women aged 40-49(3).  We support the Amereican College of Radiology and Society of Breast Imaging recommendation for annual mammography beginning at age 40.   

4.  Considering that almost a third of women imaged and biopsied at our institution were diagnosed based on a palpable concern, we reject USPSTF’s recommendations against teaching self breast exam and clinical breast exams and suggest palpation of the breasts are critical to breast cancer detection.


The paradigm used by insurance companies to authorize breast MRI needs to be reassessed.   Many companies will not authorize breast MRI unless a biopsy-proven cancer has been diagnosed, permitting coverage only for extent of disease evaluation.  We strongly support the use of breast MRI in two additional scenarios: to screen dense breasts (since it is the most efficacious modality), and to determine the need for core biopsy of indeterminate or suspicious sonographic nodules  (since non-enhancement on MRI obviates the need for biopsy).


1.     Sanders LM,  King AB, Goodman KS.  Impact of the New Jersey Breast Density Law on Imaging and Intervention Volumes and Breast Cancer Diagnosis.  J Am Coll Radiol 2016: 13:1189-1194

2.     Strobel K, Schrading S, Hansen NL et al.  Assessment of BI-RADS 4 lesions detected with screening mammography and screening US: utility of MR imaging. Radiology 2015; 274:343-351.

3.     Kopans, DB. The Recent US Preventive Services Task Force Guidelines Are Not Supported by the Scientific Evidence and Should Be Rescinded. J Am Coll Radiol 2010 7:260-264.