Among postmenopausal women, breast cancers diagnosed following biennial mammography intervals are no more “unfavorable” than those diagnosed following annual intervals, according to a report published online Oct. 20 in JAMA Oncology.
“When considering recommendations regarding screening intervals, the potential benefit of diagnosing cancers at an earlier stage must be weighed against the increased potential for harms associated with more frequent screening, such as false-positive recalls and biopsies, which are 1.5 to 2 times higher in annual vs. biennial screeners,” wrote Diana L. Miglioretti, Ph.D., of the University of California, Davis, and her associates in the Breast Cancer Surveillance Consortium (BCSC).
Dr. Cecil Fox/National Cancer Institute
The optimal frequency of mammographic screening remains controversial. The American Cancer Society commissioned the BCSC to analyze the most recent information on this issue as part of its effort to update the ACS guideline for breast cancer screening for women at average risk.
BCSC registries collect patient and clinical data from community radiology facilities across the country. For this analysis, Dr. Miglioretti and her colleagues focused on 15,440 women aged 40-85 years in these registries who were diagnosed as having breast cancer from 1996 to 2012. A total of 12,070 of the women underwent annual mammographic screening and 3,370 underwent biennial mammographic screening.
Among premenopausal women, those diagnosed after biennial mammograms were more likely to have tumors with unfavorable prognostic characteristics than were those diagnosed after annual mammograms (relative risk, 1.11). In contrast, among postmenopausal women, those diagnosed after biennial mammograms were not more likely to have tumors with unfavorable prognostic characteristics than were those diagnosed after annual mammograms (RR, 1.03), the investigators wrote (JAMA Oncol. 2015 Oct 20. doi: 10.1001/jamaoncology.2015.3084).
In an editorial accompanying this report, Dr. Wendy Y. Chen of Brigham and Women’s Hospital, Dana Farber Cancer Institute, and Harvard Medical School, all in Boston, wrote, “Although the authors do not endorse annual or biennial screening, they imply that biennial screening would be acceptable for postmenopausal women but inferior for premenopausal women.”
Most developed countries outside the United States – including the United Kingdom, Canada, and Australia – recommend screening every 2 or 3 years, Dr. Chen noted (JAMA Oncol. 2015 Oct 20 doi: 10.1001/jamaoncology.2015.3286).
This study and others clearly show that, with less frequent mammography, breast cancers will be larger and have a slightly more advanced stage when they are discovered, Dr. Chen wrote. But with a better understanding of tumor biology and improvements in targeted therapy, the best approach may not be simply trying to identify a smaller tumor, she added.
“Efforts should be focused on a better understanding of how screening interacts with tumor biology with a better understanding of the types of interval cancers and sojourn times and how these characteristics differ by age and/or menopausal status,” Dr. Chen wrote.
This study was supported by the American Cancer Society and the National Cancer Institute. Dr. Miglioretti reported having no relevant financial disclosures. One of the investigators reported being an unpaid advisor on General Electric Health Care’s breast medical advisory board.