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A study published in JAMA Oncology found that pre-menopausal women who were diagnosed with breast cancer following a biennial screening mammogram were likely to have more advanced tumors than woman screened annually. UNC Lineberger researcher Louise Henderson was a co-author on the study, which was co-led by researchers at the University of California-Davis School of Medicine and the Dana-Farber Cancer Institute.

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ouise M. Henderson, MSPH, PhD, is a UNC Lineberger member and assistant professor in the UNC School of Medicine Department of Radiology.

Premenopausal women diagnosed with breast cancer following a biennial screening mammogram were more likely to have bigger, more advanced tumors than women screened annually, according to a study published online by the journal JAMA Oncology. In contrast, the study also found that postmenopausal women not using hormone therapy had a similar proportion of tumors with less favorable prognostic characteristics regardless of whether their screening mammogram was biennial or annual.

“The results of this study suggest that menopausal status may be more important than age in determining screening intervals for breast cancer screening,” said Louise M. Henderson, MSPH, PhD, a UNC Lineberger member and assistant professor in the UNC School of Medicine Department of Radiology. Henderson was a co-author on the study, which was led by researchers at the University of California- Davis School of Medicine and the Dana-Farber Cancer Institute.

Screening mammography intervals remain under debate in the United States. Recently on Tuesday, the American Cancer Society published new guidelines that increased the age that women are recommended to begin yearly mammograms from 40 to 45. Starting at age 55, the society recommended that women have mammograms every other year. The results of the study examining menopausal status as well as a review of existing evidence on screening mammography and outcomes were used to develop the new recommendations Henderson, but they did not directly influence the change in starting age.

In the study co-led by Diana L. Miglioretti, Ph.D., of the University of California-Davis School of Medicine, researchers compared the proportion of less versus more favorable tumor prognostic characteristics in women with breast cancer who had annual versus biennial screening mammograms by age, menopausal status and postmenopausal hormone therapy (HT) use. The authors update previous analyses by using narrower intervals for defining annual (11to 14 months) and biennial (23 to 26 months) screening.

The authors used data from Breast Cancer Surveillance Consortium and included a total of 15,440 women (ages 40 to 85) with breast cancer diagnosed within one year of an annual or within two years of a biennial screening mammogram. The Carolina Mammography Registry, housed at UNC-Chapel Hill, is a member of the national Breast Cancer Surveillance Consortium. Breast imaging data from participating Carolina Mammography Registry imaging facilities throughout North Carolina were included in the study, along with data from five other breast imaging registries across the United States.

The authors defined less favorable prognostic characteristics as tumors that were stage IIB or higher, bigger than 15 millimeters, positive lymph nodes and any one or more of these characteristics.

Among the 15,440 women with breast cancer, most were 50 or older (13,182 or 85.4 percent), white (12,063 or 78.1 percent) and postmenopausal (9,823 or 63.6 percent). Women who had biennial screening mammograms were more likely to be in the youngest (40 to 49) or oldest (70 to 85) age groups and less likely than women screened annually to have a family history of breast cancer.

Premenopausal women (2,027 or 13.1 percent) had higher proportions of ductal carcinoma in situ (DCIS) vs. invasive cancers and invasive tumors with less favorable prognostic characteristics than postmenopausal women. Among premenopausal women, women screened biennially vs. annually had a higher proportion of stage IIB or higher tumors (25.7 percent vs. 19.8 percent), tumors greater than 15 millimeters (65.3 percent vs. 54.6 percent) and node-positive disease (36.6 percent vs. 31.3 percent), the results show.

Differences in these tumor characteristics among postmenopausal women were small and inconsistent, regardless of HT use, and the differences in women taking postmenopausal HT were not statistically significant, the study reports. The proportions of tumors with less favorable prognostic characteristics were not significantly larger for postmenopausal women not taking HT who were screened biennially or annually.

The authors note their study did not measure breast cancer mortality so they do not know if increases in the proportions of less favorable tumors with biennial vs. annual screening would result in differences in breast cancer mortality.

“Our findings suggest that menopausal status may be more important than age when considering breast cancer screening intervals, which is biologically plausible. … Our findings of a lower proportion of less favorable tumors with more frequent screening in premenopausal women, and no statistically significant difference in the proportion of less favorable tumors in postmenopausal women by screening interval, add to evidence about the potential benefits and harms of screening that policymakers can use to set guidelines about screening intervals and women can use when making personal screening decisions with their clinicians,” the authors conclude.

(JAMA Oncol. Published online October 20, 2015. doi:10.1001/jamaoncol.2015.3084. Available pre-embargo to the media at https://media.jamanetwork.com.)

Editor’s Note: An author made a conflict of interest disclosure. This research was supported by the American Cancer Society. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.