February 5, 2013

Biennial and yearly mammograms give older women same benefit

Yearly test leads to more false-positive results, BCSC researchers find

Seattle, WA—Among older women, getting a mammogram every two years was just as beneficial as getting a mammogram annually, and led to significantly fewer false-positive results, according to a Breast Cancer Surveillance Consortium (BCSC) study including patients and researchers from Group Health. The national study of more than 140,000 women between ages 66 and 89 is in the Journal of the National Cancer Institute.

Group Health Research Institute co-authors were Senior Investigator Diana L. Miglioretti, PhD, also of the University of California at Davis; Assistant Investigator Rebecca A. Hubbard, PhD, also of the University of Washington School of Public Health; Assistant Investigator Karen J. Wernli, PhD; Research Associate Ellen S. O'Meara, PhD; and Biostatistician Weiwei Zhu, MS.

“Screening every other year, as opposed to every year, does not increase the probability of late-stage breast cancer in older women,” said lead author Dejana Braithwaite, PhD, a UC San Francisco (UCSF) assistant professor of epidemiology and biostatistics. “Moreover, the presence of other illnesses such as diabetes or heart disease made no difference in the ratio of benefit to harm.”

From 1999 to 2006, data were collected on 2,993 older women with breast cancer and 137,949 women without breast cancer—“the largest available screening mammography data set in the United States,” according to Dr. Brathwaite. The data were obtained from five BCSC mammography registries in Washington (Group Health), California, North Carolina, New Hampshire, and Vermont.

The researchers found no difference in rates of late-stage breast cancer between women screened annually and women screened biennially.

However, they found that 48 percent of women between the ages of 66 and 74 who were screened every year had false-positive results, while 29 percent of women in the same age range who were screened every two years had false positives. With false positives, women without cancer are called back for more testing, including biopsies and more mammograms.

“Women aged 66 to 74 years who choose to undergo screening mammography should be screened every two years,” said senior author Karla Kerlikowske, MD, a professor of medicine at UCSF and a physician at the UCSF-affiliated San Francisco VA Medical Center. “They get no added benefit from annual screening, and face almost twice the false positives and biopsy recommendations, which may cause anxiety and inconvenience.”

Dr. Braithwaite noted that the study “fills an important information gap, since accountable care organizations do not address screening intervals or screening cessation in women of advanced age or with a significant burden of illness.” Accountable care organizations (ACOs) are alliances between that seeks to tie reimbursements of providers to quality metrics and reducing the total cost of care for a population of patients.

Taken together, Dr. Braithwaite concluded, “these results point to a need to consider life expectancy and co-existing illnesses in informing future recommendations about cancer screening in the elderly.”

Other co-authors of the study include Berta Geller, EdD, and Kim Dittus, MD, PhD, of the University of Vermont; Dan Moore, PhD, of UCSF; and Jeanne Mandelblatt, MD, MPH, of Georgetown University.

The study was supported by funds from the National Cancer Institute of the National Institutes of Health (CA150007, CA148577), the National Cancer Institute-funded Breast Cancer Surveillance Consortium (CA63740, CA86076, CA86082, CA63736, CA70013, CA69976, CA63731, CA70040, HHSN26120110031C), the American Cancer Society and the Agency for Healthcare Quality and Research.

Breast Cancer Surveillance Consortium

The Breast Cancer Surveillance Consortium (BCSC) is the nation's largest and most comprehensive collection of breast cancer screening information. It's a research resource for studies designed to assess the delivery and quality of breast cancer screening and related patient outcomes in the United States. The BCSC is a National Cancer Institute-funded collaborative network of seven mammography registries with linkages to tumor and/or pathology registries. The network is supported by a central Statistical Coordinating Center.

UC San Francisco

UC San Francisco (UCSF) is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care.

About Kaiser Permanente Washington Health Research Institute

Kaiser Permanente Washington Health Research Institute (KPWHRI), formerly Group Health Research Institute, improves the health and health care of Kaiser Permanente members and the public. The Institute has conducted nonproprietary public-interest research on preventing, diagnosing, and treating major health problems since 1983. Government and private research grants provide our main funding. Follow KPWHRI research on Twitter, Facebook, Pinterest, LinkedIn, or YouTube. For more information, go to: www.kpwashingtonresearch.org.

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Karen Wernli, PhD

Associate Investigator
Kaiser Permanente Washington Health Research Institute

Ellen O'Meara, PhD

Research Associate
Kaiser Permanente Washington Health Research Institute

Weiwei Zhu, MS

Biostatistician III
Kaiser Permanente Washington Health Research Institute


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