Annual Mammography Screening Offers Women of All Ages Same Benefits

Both pre- and post-menopausal women who undergo annual screening mammography have fewer late-stage breast cancer diagnoses, fewer interval cancers, and smaller average tumor size.

Women who undergo annual screening mammography beginning at age 40 have lower-stage breast cancer at diagnosis and have fewer interval cancers that women who have biennial or non-annual screenings.

Amidst the ongoing debate around at what age and at what interval women should have mammograms, these findings support earlier and more frequent screenings.

“Despite the large number of lives saved because of cancer detection with screening mammography, controversy persists regarding screening frequency for women at average risk for breast cancer,” said a team led by Mark A. Helvie, M.D., FACR, radiology professor and director of breast imaging at the University of Michigan Rogel Cancer Center. “In this study, among all women and among post-menopausal women analyzed separately, annual screening was associated with lower [American Joint Committee on Cancer (AJCC)] stage, fewer interval cancers, and smaller mean tumor size compared with biennial or non-annual screening.”

The multi-institutional team published their findings in the May 6 American Journal of Roentgenology.

Currently, there is little consensus about when women should begin mammography screening. Recommendations range from annual screening beginning at age 40 – supported by both the American College of Radiology (ACR) and the National Comprehensive Cancer Network (NCCN) – to biennial screening for women ages 50 to 74 proposed by the U.S. Preventive Services Task Force.

To offer some clarity on which screening interval offers the best performance, Helvie’s team examined screening mammography records of 245 women ages 40-to-84 scanned between Jan. 1, 2016, and Dec. 31, 2017, who had mammographically detectable or clinically palpable interval primary breast cancer. Of the group, 200 (81.2 percent) had annual screening (every nine-to-15 months), 32 (13.1 percent) had biennial scans (every 21-to-27 months), and 13 (5.3 percent) had triennial (every 33-to-39 months) screening. Together, biennial and triennial screenings were considered non-annual.

Based on the analysis of 14 fellowship-trained breast radiologists, the team determined that annual screening offered women the most benefit. For women of all ages, annual screening was associated with fewer late-stage cancer presentations, a lower likelihood of interval cancers, and smaller average tumor diameter.

Screening Outcomes for Women of All Ages

CharacteristicAnnual (n=200)Biennial (n=32)Non-annual (n=45)
Late-Stage Cancer24%43.8%44.4%
Interval Cancer10%37.5%33.3%
Mean Tumor Size1.4cm +/- 1.2cm1.8cm +/- 1.6cm1.8cm +/- 1.5cm

These findings held true for post-menopausal women, as well. Of the 191 post-menopausal women included in the study, those who were screened annually had less late-stage cancer, fewer interval cancers, and small average tumor diameters. These outcomes are important, the team noted, because previous research has not identified these benefits in this patient group.

Screening Outcomes for Post-Menopausal Women

CharacteristicAnnual (n=159)Biennial (n=24)Non-annual (n=8)
Late-Stage Cancer23.9%45.8%43.8%
Interval Cancer10.1%45.8%37.5%
Mean Tumor Size1.3cm +/- 1.0cm1.8cm +/- 1.6cm1.8cm +/- 1.6cm

The team noted that interval cancers have a two-fold higher hazard ratio for death than screening-detected cancers. In addition, they said, larger tumor size is an independent predictor of increased mortality.

The team found no statistically significant differences in the frequency of axillary lymph node positivity among interval groups, as well as no statistical differences in pathologic diagnosis. Also, while not statistically significant, annually screened women were less likely to undergo any axillary nodal surgery, showed less frequency use of chemotherapy, and used hormone therapy less frequently. Biennially- and non-annually screened women demonstrated greater use of axillary lymph node dissection.

“Our data show that breast cancers diagnosed in the setting of annual screening require less extensive treatment, which is not surprising given the lower AJCC stage, fewer interval cancers, and smaller mean tumor size,” the team said. “The results of this study support the recommendation for annual screening mammography for pre- and post-menopausal patients, consistent with annual screening recommendations by the ACR and the NCCN, which recommend screening initiation at age 40-years-old.”

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