Publicado por Ricardo Alexandre de Souza em http://medicinadefamiliabr.blogspot.com
Biennial Mammography Reduces False-Positive Results
Clinical ContextFalse-positive recalls occur for 14% of women at first mammography screening and 8% at subsequent examinations. Women will undergo 12 screening mammography examinations in their lifetimes if they start biennial mammography screening at 50 years and stop at age 74 years, and 24 if they start annual screening at 50 years. Estimates of the probability that a woman will receive a false-positive reading range from 29% to 77% and are 8% to 9% for benign biopsy readings.
This is a longitudinal cohort study of women who received mammograms between 1994 and the most recent year, with complete breast cancer capture. The study assesses the rate of false-positive findings with annual and biennial screening.
Study Synopsis and PerspectiveWomen who undergo routine annual screening mammography carry a higher risk for false-positive findings leading to unnecessary follow-up tests and biopsy recommendations than women who receive screening mammography every other year, according to an evaluation of National Cancer Institute registries involving nearly 170,000 patients.
The prospective cohort study, published in the Annals of Internal Medicine, determined that women who undergo routine annual screening mammography have a 61.3% chance of receiving at least 1 false-positive recall for suspected breast cancer every 10 years compared with a 41.6% probability for women who receive biennial screening mammography.
Rebecca A. Hubbard, PhD, an assistant investigator at the Group Health Research Institute, Seattle, Washington, and collaborators from the H. Moffitt Cancer Center, Tampa, Florida; University of Missouri, Columbia; and University of California, San Francisco, compiled these data from the 10-year clinical experience of 169,456 women tracked by 7 mammography registries funded by the National Cancer Institute's Breast Cancer Surveillance Consortium.
The findings appear to lend credence to the US Preventive Service Task Force's controversial recommendation in 2009 favoring biennial screening mammography for women aged 50 to 74 years. The task force challenged the accepted standard of annual X-ray screening mammography for women beginning at age 40 years as a front-line diagnostic strategy for reducing breast cancer mortality. Its pronouncement sent a shockwave through the international medical community about the optimal timing for screening mammography.
Dr. Hubbard's study may add fuel to that debate: It found the likelihood that a woman would receive a biopsy recommendation, based on false-positive findings, was significantly higher for annual mammography than biennial screening.
The 10-year probability of a false-positive biopsy recommendation for women who started annual mammography in their 40s and 50s was 7.0% and 9.4%, respectively. The risk was 4.8% over 10 years for women who began to receive biennial screening mammography in their 40s and 6.4% when women initiated their annual exams in their 50s.
A slightly larger proportion of women screened every 2 years was diagnosed with late-stage cancer; however, the difference was not statistically significant.
For both age groups, 24.6% of the diagnosed cancers were characterized as "late stage" for women receiving biennial screenings compared with 21.3% for women who initiated annual screening in their 40s and 21.9% of women who started receiving annual mammography in their 50s.
"Biennial screening thus decreases risks," the authors write, "but may also attenuate the benefits of routine screening."
In an editorial published with the study, Philippe Autier, MD, director of the International Prevention Institute, Lyon, France, placed Dr. Hubbard's finding into context with the balancing act between efficiency and efficacy that always seems to foment controversy for widely applied screening exams.
"Taken together, available evidence does not demonstrate that a shorter screening interval prevents advanced disease or reduces breast cancer mortality," he writes. "However, as Hubbard and colleagues demonstrate, a shorter screening interval leads to more false-positive screening results and may also lead to greater detection of small, non–life-threatening cases of cancer."
Dr. Autier concludes that mammography screening every year is less efficient than screening every 2 years or more.
The study was supported by grants from the National Cancer Institute. Several of the authors receive grant funding from National Cancer Institute and from the National Institutes of Health. One author reports receiving payment for the development of educational programs for Oakstone Publishing.
Ann Intern Med. 2011;155:481-492; 554-555. Article abstract, Editorial extract
The full text of the Screening for Breast Cancer: U.S. Preventive Services Task Force Recommendation Statement is available online.
- The study used data from 7 Breast Cancer Surveillance Consortium registries in the National Cancer Institute–funded Breast Cancer Surveillance Consortium.
- Participants were women who underwent first screening mammography at age 40 to 59 years between 1994 and 2006 (n = 169,456) and women who had a diagnosis of invasive breast cancer between 1994 and 2006 (n = 4492)
- The registries collected demographic information and radiologists' assessments using the American College of Radiologist's Breast Imaging and Reporting and Data System.
- Each of the 7 registries is linked to the Surveillance, Epidemiology, and End Results database, which is used to determine cancer status after mammography.
- 6 of the 7 sites also had links to the pathology database.
- A separate cohort was constructed for analysis of cancer stage consisting of women aged 40 to 59 years at the time of incident invasive breast cancer between 1996 and 2006.
- Screening interval was defined using self-report by the participants and information from the Breast Cancer Surveillance Consortium database.
- Annual screening was defined as screening intervals of 9 to 18 months.
- Biennial screening was defined as a screening interval of between 19 and 30 months, and longer than biennial screening was any interval greater than 30 months.
- A recall biopsy recommendation was considered false-positive when there was no diagnosis of invasive carcinoma or ductal carcinoma in situ within 1 year of the screening examination or before the next screening mammogram, whichever was earlier.
- Included were 386,799 mammograms from 169,456 women interpreted by 997 radiologists.
- 47.7% of women had only 1 screening mammogram; 11.8% had 5 or more examinations.
- Most mammograms (78.9%) were for women aged 40 to 49 years at first mammogram.
- Median age at first screening was 42 years for women who started in their 40s and 53 years for women who started in their 50s.
- Among subsequent mammograms, 55.6% occurred at annual screening and 27.6% occurred at biennial screening.
- Most mammograms were assessed as benign or negative.
- Those women with initial Breast Imaging and Reporting and Data System scores of 0 were considered in need of additional screening.
- The probability of false-positive recall was 16.3% for first and 9.6% for subsequent mammograms.
- The false-positive recall rate was higher in women who started screening more recently, those with heterogeneously dense breasts, and for first examinations, older women and those with a positive family history of breast cancer.
- The availability of a previous mammogram for comparison reduced the risk for a false-positive recall by 50% (odds ratio, 0.50).
- For a woman who started screening at age 40 years, the cumulative probability of false-positive recall after 10 years was 61.3% with annual screening and 41.6% with biennial screening.
- For a woman who started screening at age 50 years, the relative probabilities were 61.3% and 42.0%, respectively.
- 7% to 9% of women received a false-positive biopsy recommendation after 10 years of annual screening.
- Among women with a diagnosis of incident invasive breast cancer, there was a nonsignificant increased risk for later diagnosis of breast cancer, with a percentage increase of 3.3%.
- The authors concluded that after 10 years of screening, there was an increased risk for false-positive recall of mammograms in women who started at 40 or 50 years, and that biennial screening reduced this risk.
- However, they also noted the small and nonsignificant increased risk of delaying a diagnosis of invasive breast cancer with biennial vs annual screening.