Digital mammography begins to deliver hope

For years, the world of breast imaging was quite simple. Screen-film mammography and ultrasound did not leap ahead, but they did a satisfactory job for most women. In the past few years, the armamentarium has exploded, with the introduction of modalities from MRI to vacuum biopsy. The management of breast disease has changed significantly.

Digital mammography has raised controversy in Europe and the U.S., especially in the screening field. Initial acceptance was quite slow, and the results of some papers were keenly contested, mainly because the gold standard, screen-film mammography, is far from perfect. Both techniques miss some cancers but not necessarily of the same type.

The American College of Radiology Imaging Network (ACRIN) study enrolled about 49,500 women and represents a milestone in digital mammography's history.¹ The initial results suggest there is a slight benefit for women with dense breasts and no clear advantage against screen-film mammography in others, digital mammography being at least equal to SFM. The open Oslo studies enrolled more than 30,000 women and showed some other advantages-lower recall rate, better specificity in certain cases, and lower dose exposure-with marginal overall superiority for digital mammography.²

Meanwhile, the debate over screening continues. A survey presented at the SOFMIS (La Societe Francaise de Mastologie et d'Imagerie du Sein) conference in June showed that screening was not uniform in the world.³ Only nine national screening programs exist in 25 EU countries, with wide differences in terms of age at screening, periodicity, second reading, and quality control. In some federally organized countries, screening may or may not exist, and it can differ from a linguistic or regional point of view (county/lander/canton). Variations also occur in heavily centralized countries. The age at which screening begins ranges from 40 to 50, and the age at which it ends differs from 69 to 74.

Kopans has shown how information can be manipulated, even by highly respected peer-reviewed journals.⁴ This leads to biases in the analysis of the results of screening campaigns and inaccurate information, notably about starting screening at the arbitrary age of 50. In France, the age for initial screening is 50, but we find nearly as many cancers in a population aged 45 to 50 as in the 50 to 55 range, and no age is specified for women with dense breasts, even without hormonal replacement therapy.

In the U.S., digital mammography accounts for 8% to 10% of the installed base. In May 2006, 865 of the 8879 accredited breast centers had 1210 digital systems. The results of the Mammography Quality Standards Act published by the Food and Drug Administration show a clear trend toward digital mammography, with a steep decline of SFM accreditation and a clear increase of digital mammography accreditation. Digital mammography was approved in 2000. Medicare has accepted some extra payment for digital mammography ($135.29 versus $85.65), as well as for computer-aided detection ($19.17), but the market remains quite sluggish as buyers wait for more evidence. The ACRIN trial triggered a great deal of interest from the general public, and coverage appeared in numerous newspapers. Many Web sites, including those of the National Cancer Institute and the Susan G. Komen Breast Cancer Foundation, are warning women not to defer their screening exams by waiting for digital mammography.

PILOT PROGRAMS

In Europe, the situation is complex because some countries are still conducting investigational studies. Some have closed pilot studies and are moving toward digital screening, and in most countries, except France, both techniques are now allowed for screening. According to some experts in the SOFMIS survey, Pisano's paper has prompted a strong tendency toward digital screening in Europe,¹ but there are no national digital screening programs. In the Netherlands, the digital program has been postponed until 2007.

Controversy about economics also persists, but very few papers are available on this topic. There are many ways of conducting a screening mammography program, and uniformity is lacking. A Swedish pilot study showed it was possible to screen 20,000 women a year and conduct 4500 diagnostic studies with a single digital full-field mammography unit staffed by two radiologists with five radiographers.⁵ A U.K. study that was conducted in 2004 that was performed with two different FFDM systems concluded that digital mammography was nearly as cost-effective as SFM when using soft-copy reading only with digital archiving.⁶

Like it or not, breast screening mammography is going digital. Many factors account for this trend, including increased pressure from industry and growing scientific evidence and public awareness. The digital equipment market is expected to grow annually by 10% to 12% for the next five years. The financial benefits still must be proven, and the organizational approach has to be modified greatly to take advantage of innovations such as digital mass storage and image distribution, as well as data-mining (eDiamond project) and the National Digital Mammography Archive. Some issues remain unresolved, but the move toward digital mammography screening looks set to change screening practice.

DR. LAVAYSSIERE is a private-practice radiologist in Sarcelles, France.

References1. Pisano E, Gatsonis C, and Hendrick E. Diagnostic performance of digital versus film mammography for breast-cancer screening. NEJM 2005;353(17):1773-1783.
2. Skaane P and Skjennald A. Screen-film mammography versus full-field digital mammography with soft-copy reading: randomized trial in a population-based screening program-the Oslo II Study. Radiology 2004;232:197-204.
3. Lavayssiere R. Revue des experiences etrangeres de depistage numerique. SOFMIS, Clermont-Ferrand, France, 2-3 June 2006.
4. Kopans DB. Informed decision making: age 50 is arbitrary and has no demonstrated influence on breast cancer screening in women. AJR 2005;185:177-82.
5. Heddson B. A complete digital workflow at the breast unit, Helsinborg Hospital, Sweden. EUSOBI, Vienna, 1-2 March 2006.
6. Legood R, Gray AM. A cost comparison of full field digital mammography (FFDM) with film screen mammography in breast cancer screening. NHS Breast Screening Programme Equipment Report 0403. February 2004. Sheffield, NHS Cancer Screening Programmes.