Women in both countries who are recalled undergo additional tests such as ultrasound, diagnostic mammography and biopsy.
The study, published in the October 22 issue of the Journal of the American Medical Association, compared screening mammography performance in the US and UK among similar aged women by examining three large-scale registries, analyzing 5.5 million mammograms.
Recall rates in the UK are substantially lower than in the US, yet there is no substantial reduction in cancer detection. Projections made by the researchers show that over ten years of screening about 40-50 percent of US women will have at least one false-positive scare, while in England only 15 percent of women will. Still, very similar numbers of cancers are detected in both countries. "The anxiety and costs associated with these false-positives can be enormous," said Smith-Bindman, a UCSF assistant professor of radiology and epidemiology and biostatistics.
"We need to find ways to improve the accuracy of mammography and training for mammographers," she added. "The goal of any cancer screening effort is to obtain high cancer detection rates while avoiding unnecessary diagnostic evaluation following false positive results. Perhaps we can learn from the UK, where half as many women without breast cancer undergo open surgical biopsies as in the US."
The National Health Service Breast Cancer Screening Program of the UK provided the researchers with records for 3.94 million mammograms. In the US, the Breast Cancer Surveillance Consortium provided 978,591 records and National Breast and Cervical Cancer Early Detection Program provided 613,388 records.
Researchers ascertained which women in the data set had developed cancer through active case follow up and linkages with state tumor registries, Surveillance Epidemiology and End Result registries, or pathology databases. Cancers, either invasive or ductal carcinoma in situ, within 12 months of a positive screening mammogram were counted.
Recall, biopsy, and other further diagnostic procedures were calculated per 100 screening mammograms. Biopsy types including fine needle aspiration, core biopsy, open surgical and unspecified were included.
The researchers noted that in the UK, the National Health Service has set and reached targets that emphasize high rates of cancer detection and low recall rates. "We attribute success in the UK to their centralized program of continuous quality improvement," said Smith-Bindman. In the US, although facilities and radiologists must comply with the Mammography Quality Standards Act/Mammography Quality Standards Reauthorization Act, no specific guidelines for interpreting mammograms are mandated.
Another factor may be the higher rate in the US of malpractice lawsuits focused on missed breast cancer diagnoses. Researchers speculated that US radiologists may recall women very conservatively based on findings with even a low likelihood of cancer in order to avoid any such potential litigation.
Researchers also characterized UK radiologists as highly experienced. While US physicians must read only 480 mammograms annually to fulfill quality standard requirements, UK radiologists are required to read at least 5000. On average, UK radiologists interpret 5-7 times more mammograms than their US counterparts.
The study was funded by the National Cancer Institute and the Department of Defense. Additional authors are Philip Chu, MS, UCSF; Diana Miglioretti, PhD, University of Washington; Edward Sickles, MD UCSF; Roger Blanks, PhD, University of London; Rachel Ballarad-Barbash, MD, MPh, National Cancer Institute; Janet Bobo, PhD, and Nancy Lee, MD, Centers for Disease Control; Matthew Wallis, MB, ChB, FRCR, Warwickshire, Solihull and Coventrey Breast Screening Service; Julietta Patnick, BA, FFPHM, National Health Service; Karla Kerlikowske, MD, UCSF.
Journal
JAMA