Low-Dose Digital Mammography May Be Accurate

Research by Chen et al suggests that low-dose techniques for digital mammography may be feasible, as results are not substantially affected by variations in radiation dose. Their study was published in Radiology.

The researchers analyzed retrospectively a cohort of women from the American College of Radiology Imaging Network Pennsylvania 4006 trial. All patients underwent breast screening with a combination of dose protocols, including standard full-field digital mammography, low-dose digital mammography, and digital breast tomosynthesis. A total of 5832 images from 486 women were analyzed with fully automated software for quantitative estimation of density.

Clinical Breast Imaging Reporting and Data System (BI-RADS) density assessment results were also available from the trial reports. The influence of image acquisition radiation dose on quantitative breast density estimation was investigated with analysis of variance and linear regression.

Radiation dose of image acquisition did not significantly affect quantitative density measurements, with percent density demonstrating a high overall correlation between protocols. However, differences in breast percent density were observed within high BI-RADS density categories, although they were significantly correlated across the different acquisition dose levels.

The authors concluded that reproducibility of automated breast density measurements with digital mammography are not affected by variations in radiation dose; thus, the use of low-dose techniques for the purpose of density estimation may be attainable.

Digital breast tomosynthesis may reduce recall rates

JAMA Oncology published McDonald et al research regarding the efficacy of digital breast tomosynthesis (DBT) on recall rates versus that of digital mammography (DM), and also its sustainability over the long term.

The study was a retrospective analysis of a total of 44468 screening events performed on 23958 women whose average age was 56 years and were followed over a period of 4 years.

Recall rates rose slightly for years 1 to 3 of DBT (88, 90, and 92 per 1000 screened, respectively) but remained significantly reduced compared with the DM zero rate of 104 per 1000 screened. The cancer cases per recalled patients continued to rise from DM zero rate of 4.4% to 6.2% for years 1 to 3 of DBT, respectively. Outcomes assessed for the most recent screening for individual women undergoing only 1, 2, or 3 DBT screenings during the study period demonstrated decreasing recall rates of 130, 78, and 59 per 1000 screened, respectively (P < .001). Interval cancer rates, determined using available follow-up data, decreased from 0.7 per 100 women screened with the use of DM to 0.5 per 1000 screened with the use of DBT.

Digital breast tomosynthesis screening outcomes are sustainable, with significant recall reduction, increasing cancer cases per recalled patients, and a decline in interval cancers.

USPSTF breast cancer screening guidelines

The United States Preventative Services Task Force (USPSTF) issued new guidelines for when and how often women should be screened for breast cancer.

The USPSTF recommends biennial screening mammography for women 50-74 years.  Women of average risk between the ages of 40 and 49 should make an individual choice about whether to initiate screening every other year.  The UUPSTF recommends against teaching self-breast examination.

       

The USPSTF’s recommendations are similar to those issued recently by the American Cancer Society.  ACR recommends initiation of annual screening at age 45 and transition to biennial at age 55 as long as a woman has life expectancy of 10 years or longer.

American Cancer Society Updated Guidelines for Breast Cancer Screening

Breast cancer is a leading cause of premature mortality among US women.   Oeffinger at al report in JAMA the American Cancer Society (ACS) 2015 update regarding the frequency of screening mammography in women at average risk. 

The ACS recommends that women with an average risk of breast cancer should undergo annual screening mammography starting at age 45 years (strong recommendation).

Women 55 years and older should transition to biennial screening (strong recommendation).

Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer (qualified recommendation).

Women should have the opportunity to have annual screening between at the ages of 40-45 received a qualified recommendation.

The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation).

These updated ACS guidelines provide evidence-based recommendations for breast cancer screening for women at average risk of breast cancer.   

USPSTF guidelines for breast cancer screening

On April 20, 2015, the U.S. Preventive Services Task Force (USPSTF) released its draft guidelines for breast cancer screening.

The USPSTF recommends biennial screening mammography for women ages 50 to 74 years.

The decision to start screening mammography in women prior to age 50 years should be an individual one. Women who place a higher value on the potential benefit than the potential harms may choose to begin biennial screening between the ages of 40 and 49 years.

•   For women at average risk for breast cancer, most of the benefit of mammography will result from biennial screening during ages 50 to 74 years. Of all age groups, women ages 60 to 69 years are most likely to avoid a breast cancer death through mammography screening. Screening mammography in women ages 40 to 49 years may reduce the risk of dying of breast cancer, but the number of deaths averted is much smaller than in older women and the number of false-positive tests and unnecessary biopsies are larger.

•   All women undergoing regular screening mammography are at risk for the diagnosis and treatment of noninvasive and invasive breast cancer that would otherwise not have become a threat to her health, or even apparent, during her lifetime (known as “overdiagnosis”). This risk is predicted to be increased when beginning regular mammography before age 50 years.

•   Women with a parent, sibling, or child with breast cancer may benefit more than average-risk women from beginning screening between the ages of 40 and 49 years.

•    The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women age 75 years and older.

•     The USPSTF concludes that the current evidence is insufficient to assess the benefits and harms of tomosynthesis (3-D mammography) as a screening modality for breast cancer.

This recommendation applies to asymptomatic women age 40 years and older who do not have pre-existing breast cancer or a previously diagnosed high-risk breast lesion and who are not at high risk for breast cancer because of a known underlying genetic mutation (such as a BRCA mutation or other familial breast cancer syndrome) or a history of chest radiation at a young age.

Benefits, Harms, and Costs of Screening with Digital Mammography

Stout et al in their article published by the JNCI, report on the economic impact digital mammography had as it has replaced film in the United States.

Their research compared digital screening strategies starting at age 40 or 50 years applied annually, biennially, or based on density with biennial film screening from ages 50 to 74 years and with no screening. Common data elements included cancer incidence and test performance, both modified by breast density. Lifetime outcomes included mortality, quality-adjusted life-years, and screening and treatment costs.

For every 1000 women screened biennially from age 50 to 74 years, switching to digital from film yielded a median improvement of 2 life-years, 0.27 additional deaths averted, 220 additional false-positive results, and $0.35 million more in costs. For an individual woman, this translates to a health gain of 0.73 days. Extending biennial digital screening to women ages 40 to 49 years was cost-effective, although results were sensitive to quality-of-life decrements related to screening and false positives. Targeting annual screening by density yielded similar outcomes to targeting by age. Annual screening approaches could increase costs to $5.26 million per 1000 women, in part because of higher numbers of screens and false positives, and were not efficient or cost-effective.

They concluded that transition to digital breast screening in the United States increased total costs for a small added health benefit.  While the value of digital mammography screening for breast cancer among women aged 40 to 49 years was cost effective the women should be cognizant of the high rate of false positives.