Challenges and Trends in Breast Cancer Screening
Martin Lindner | 03-10-2016
Despite considerable controversy around the world, mammography has become the standard for the systematic early detection of breast cancer. New imaging technologies and the trend toward personalized medicine are ushering in a new era of screening.
Challenge: Breast cancer is the most common cancer in women worldwide, and the number of women affected continues to rise. This requires efficient early detection. However, mammography screening, which is an established procedure in many countries, can also lead to inconclusive test results and to treatment for slow-growing cancers that would not have caused a problem.
Solution: Personalized, risk-adapted screening and therapy could overcome these difficulties to some extent. In addition, a new imaging technology called tomosynthesis is now available that is possibly superior to mammography.
Results: Breast cancer screening options are increasing and are changing the practice of early detection in industrialized countries. Meanwhile, countries like China, India, and Brazil are trying to develop cost-effective screening strategies that are adapted to their needs.
The Rise of Mass Screening Programs
Breast cancer screening is currently a global standard of preventive medicine.1 Debates on the pros and cons have been raging since it was introduced in the early 1970s – and are far from over. Parallel to Western industrialized nations, interest in screening is also becoming increasingly common in countries such as China, Saudi Arabia, and Brazil. At the same time, new imaging technologies and the trend toward personalized care and treatment are gaining ground internationally. What does the future hold for breast cancer screening?
Screening mammograms have been a long-standing practice in North America, Europe, Australia, and Japan. “The strategy provides many important advantages,” confirms mammography screening expert Sylvia Heywang-Köbrunner, who recently contributed to the current position on the subject adopted by the International Agency for Research on Cancer (IARC).2 According to Heywang-Köbrunner, there is strong evidence that a significant number of breast cancer deaths can be prevented through regular mammogram screenings and more timely treatment.
Milestones of a Medical Paradigm
“Breast cancer screenings can be compared to other prevention efforts, such as those for high blood pressure or diabetes,” comments radiologist Ingvar Andersson from Lund University in Malmö, Sweden. One of the field’s pioneers, Andersson has been researching different screening exams since the 1970s and is currently working for the diagnostic company Unilabs, which is responsible for the screening program in southern Sweden.3 Andersson recalls that, in addition to the development of specialized X-ray devices and sensitive screen-film combinations in the 1960s and 1970s, the roots of this medical paradigm also lie in the Health Insurance Plan Study in New York. The long-term study, which began in 1963, showed the efficacy of mass screenings for breast cancer over an observation period of many years.4
Further randomized trials in Sweden and elsewhere confirmed the effect, and technology also improved, particularly with the introduction of digital mammography in early 2000. Today, more than two dozen countries around the world have breast cancer screening programs. “Knowledge about breast cancer and the possibilities of screening are also much more firmly anchored in the minds of women,” adds Andersson. According to the latest IARC scientific paper, the risk of dying from breast cancer has dropped by more than 20% in areas where women have access to screening mammograms, and by as much as 40% among women who actually participate and undergo screening mammograms regularly.
The Problems of a Mass Screening Program
Nevertheless, the controversy about breast cancer screenings is by no means resolved. Some critics consider the benefits of comprehensive routine mammography outside clinical studies to be debatable.5 Others argue that the original large preventive effect of the screening has decreased in the last few decades. Because many breast cancer tumors can be treated more effectively today, very early diagnosis is no longer as important as it used to be.6
Even proponents of population-wide screening programs admit that the approach presents specific problems. For example, most women who take advantage of screenings do not develop breast cancer, but some may find themselves confronted with an inconclusive or suspicious finding in the initial screening mammogram – leading to a so-called recall.
Recalls and Overdiagnoses
Heywang-Köbrunner says it is estimated that on average one in five women who regularly participate in an organized mammography program for 20 years receives one recall during these 20 years. Most initial suspicions can be dispelled by a harmless additional test, such as another mammogram or an ultrasound examination. However, the uncertainty associated with these so-called false positive diagnoses can cause women a great deal of anxiety while they wait. “The psychological effects should not be ignored,” states Andersson.
“However, the most significant problem is overdiagnosis,” she adds. By this, she means tumors that would never be noticed without screening but once detected will typically result in surgery and radiation. Reasons why they would not have been detected include very slow tumor growth or early death from another cause. Estimates for the total number of overdiagnoses are difficult to determine and depend heavily on the defined period of observation. What is clear, though, is that for all women whose lives were saved by a screening, there were others who had to undergo treatment that in retrospect may have been unnecessary.
An International Comparison of Screening Programs
According to a 2012 survey by the International Cancer Screening Network, more than two dozen countries worldwide have organized breast cancer screening programs.7
After the first pilot projects in 1977 in Japan, the approach spread to North America, Europe, and Australia in the 1980s and 1990s. More recently, it arrived in countries such as China, Singapore, Saudi Arabia, and some parts of Brazil.8 In a global comparison, there are differences as well as similarities.
For example, women in the Scandinavian countries, the United Kingdom, and Germany receive a personal invitation for screening at predetermined intervals. In other countries, by contrast, the participants are recruited through media campaigns or referred by their doctor. The screening programs are only available in limited regions of China, Saudi Arabia, Spain, and Switzerland.
One special case is opportunistic screening, in which women undergo the exam at their request or as part of routine medical care. Opportunistic screening plays an important role in the United States, for example. In Latin America, where there are national screening recommendations but no organized mammography programs, most screenings are performed at the patient’s request, and often by a private-sector doctor.9 The main problems with opportunistic screenings are that the necessary intense training of the personnel and the quality assurance of imaging, image interpretation, and further work-up are not generally guaranteed to be at the same level as in organized screening programs. This typically leads to higher risks of side effects and higher costs without proof of a comparable effect.
Mammography is the standard screening technology around the world, and is sometimes supplemented by the doctor palpating the breast or examining it with ultrasound. Special centers, general medical facilities, and sometimes mobile screening units perform the examinations, normally at two-year intervals. Many organized programs concentrate on patients between the ages of 50 and 70, but women are routinely screened starting at the age of 40 and after the age of 70 in Sweden, Australia, South Korea, Japan, and the United States. The participation rates also vary considerably. They stand at almost 20% in Japan and Saudi Arabia, at around 50% in Canada and Switzerland, and at over 80% in the Netherlands and Finland.
Trends and New Technologies
These difficulties can be partly remedied by new strategic approaches. “In the future, the screening will be more personalized than it is now,” predicts Andersson. He explains that the individual cancer risk is likely to be evaluated more precisely based on genetic analyses or biomarkers. This could then influence the type and intensity of the screening and help avoid unnecessary treatment. Imaging technologies are also changing. Heywang-Köbrunner explains that breast tomosynthesis is an important innovation. The ability to view the breast in slices rather than as a single projection helps tumors to be detected more often and earlier, and to be more clearly defined.
“A combination of tomosynthesis and ultrasound in one and the same device would also be beneficial,” says Andersson. Such customized hardware could be very advantageous for efficient screening in women with dense breast tissue, for example. Andersson also suggests another idea: Software for routine use in computer-assisted tumor detection. “One important barrier to mammography screening is a lack of competent radiologists prepared to read a large number of normal mammograms daily,” he says. “A computer-assisted detection (CAD) system that could rule out breast cancer with a high degree of accuracy and thus relieve radiologists from reading a significant proportion of screening mammograms would be highly desirable.”
About the Author
Martin Lindner is an award-winning science writer based in Berlin, Germany. He went into journalism after studying medicine and earning a PhD in the history of medicine. His articles have appeared in many major German and Swiss newspapers and magazines.
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2Interview with Sylvia Heywang-Köbrunner, Vienna, Austria, March 2, 2016
Lauby-Secretan B, Scoccianti C, Loomis D, et al. (2015) Breast-cancer screening – viewpoint of the IARC Working Group.
3Telephone interview with Ingvar Andersson, February 18, 2016
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Ciatto S, Houssami N, Bernardi D, et al. (2013) Integration of 3D digital mammography with tomosynthesis for population breast-cancer screening (STORM): a prospective comparison study. Lancet Oncol 14:583-9
6Welch HG (2010) Screening mammography – a long run for a short slide? N Engl J Med 363:1276-8
7ternational Cancer Screening Network: Breast Cancer Screening Programs in 26 ICSN Countries, 2012: Organization, Policies, and Program Reach. http://healthcaredelivery.cancer.gov/icsn/breast/screening.html (accessed March 8, 2016)
8De Castro Mattos JS, Mauad EC, Syrjänen K, et al. (2013) The impact of breast cancer screening among younger women in the Barretos Region, Brazil. Anticancer Res 33:2651-5
Caleffi M, Ribeiro RA, Bedin AJ Jr, et al. (2010) Adherence to a breast cancer screening program and its predictors in underserved women in southern Brazil. Cancer Epidemiol Biomarkers Prev 19:2673-9
Loy EY, Molinar D, Chow KY, Fock C (2015) National Breast Cancer Screening Programme, Singapore: evaluation of participation and performance indicators. J Med Screen 22:194-200
9International Agency for Research on Cancer (2002) Breast Cancer Screening – IARC Handbook of Cancer Prevention Volume 7 (Chapter 3). http://www.iarc.fr/en/publications/pdfs-online/prev/handbook7/ (accessed March 12, 2016)
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