Researchers are inviting legions of women to step forward for a high-tech showdown between two types of mammography used to detect breast cancer: tried-and-true film mammography and newer digital mammography, which generates images like a digital camera.

The Digital Mammographic Imaging Screening Trial (DMIST) is a $26.3 million effort funded by the National Institutes of Health’s National Cancer Institute. Co-sponsored by the American College of Radiology Imaging Network, it will take place at 19 test sites housed in 18 institutions in the US and Canada.

The 49,500 female volunteers who participate will receive a conventional screening mammogram along with a digital screening.

Digital mammograms hold the promise of many advantages after a cancer is detected, says Etta Pisano, MD, principal investigator at the University of North Carolina (UNC) at Chapel Hill.

But it remains unproven whether the far costlier digital mammograms are better, worse, or equal to film at finding early tumors. Film mammography has been instrumental in saving so many women’s lives, says Pisano, co-director of the breast cancer program at the UNC School of Medicine’s Lineberger Comprehensive Cancer Center.

Women and their doctors should know the differences in diagnostic accuracy, Pisano says, before demanding a hot new technology that may not, in fact, detect breast cancers as well as conventional mammography.

Comparisons between the methods are complicated, Pisano says, but film offers finer detail, while digital excels at distinguishing between shades of gray. The study will show which attribute is more important for detection.

The American Cancer Society (ACS) encourages women to join the trial, says Robert Smith, PhD, director of cancer screening for the ACS. “It’s an enormous service to help answer this important clinical question,” he says.

Meanwhile, mammography machines have a six-to-eight year lifespan, and health organizations are asking which technology to buy next: film or digital. “We want to have proof before every mammography unit is replaced,” Pisano says.

The 49,500 volunteers are needed because most women screened will not have cancer. Statistically, Pisano says, researchers expect to find four-to-seven cancers per 1,000 women in the general “screening population” —women without symptoms who are due for a scheduled mammogram.

“Absolutely, we need women to participate,” Pisano says. “We need them to be altruistic. This will help their daughters, their mothers, their sisters, women they care about.”

The process of a digital mammogram is no different from film. The same technologist will conduct both exams, compressing the breasts between plates and taking at least two views per breast.

Screening tests, including mammograms, are judged by several measures, says Smith.

• Sensitivity is key: How reliable is the mammogram at detecting tumors?
• Specificity is another yardstick: Does the test produce too many false alarms resulting in callbacks for additional screenings and biopsies?
• And is it cost effective: Do mammograms save lives and prevent illness to an extent that justifies their price tag? (A digital mammogram costs about four times as much as film.)

At the end of the study, Smith says, scientists will know if digital offers unique clinical advantages, or if film is superior in more ways than just price. “Participating in this study does not involve any risk of a less-accurate mammogram, because they are getting both,” says Smith. “And study coordinators will act on a positive finding, no matter the imaging technique they use.”

The 18 institutions will enroll their own participants – most will start accruing volunteers on Oct. 15. Investigators expect to wrap up enrollment within 18 months. Pisano anticipates having answers in 2004.

A list of participating institutions follows. For contact information at each site and entrance requirements, go to the Digital Mammographic Imaging Screening Trial.

The study sites are located at: Beth Israel Deaconess Medical Center in Boston; Columbia University in New York; Good Samaritan Hospital Medical Center in West Islip, N.Y.; Johns Hopkins University in Baltimore; LaGrange Memorial Hospital in LaGrange, Ill.; Memorial Sloan Kettering in New York; Mt. Sinai Medical Center in New York; Northwestern University in Chicago; Thomas Jefferson University in Philadelphia; University of California Davis; University of California Los Angeles; University of Colorado Health Sciences Center in Denver; University of Massachusetts in Worcester, Mass.; University of North Carolina in Chapel Hill (host of two sites for the study); University of Pennsylvania in Philadelphia; University of Toronto in Ontario, Can.; University of Washington in Seattle; and Washington Radiology Associates, PC, in Washington, D.C.