A multicenter study has found that digital mammography is more accurate than standard film techniques at screening women under 50 or those who have very dense breasts for cancer.

But fewer than one out of 10 mammography units in the country are digital, noted Dr. Willliam Poller, associate director of the breast care centers at Allegheny General Hospital and one of the study investigators.

So even if women wanted it, "we couldn't image them all using digital techniques because [the units] aren't there to do it," he said.

Dr. Etta Pisano, of the University of North Carolina at Chapel Hill, presented the findings yesterday at a meeting of the American College of Radiology Imaging Network in Pentagon City, Va. The report will be published in the New England Journal of Medicine next month.

Nearly 43,000 women at 33 centers in the United States and Canada participated in the trial. About 570 women were studied at Allegheny General, which was the only Pittsburgh site.

The women had digital and film mammograms done at the same sitting. Different radiologists interpreted each set of images without knowing what the other set showed. Screenings were repeated about one year later and biopsies of suspicious lesions were performed if either doctor recommended it.

Digital and film mammography were equivalent in screening women who were older than 50, did not have dense breast tissue and were post-menopausal.

But digital mammography was more accurate for women who were under 50, or who were of any age with dense breast tissue or who were premenopausal.

Women cannot judge how dense their breasts are, Poller cautioned.

"She wouldn't know," he said. "It's not how it feels, it's how it looks inside."

If a woman has had a mammogram within the last year, she need not get another one done using digital means, he said. But she might want to contact her doctor to find out if the mammography report indicated she had dense breasts so that she can plan for her next exam.

Poller said that digital mammography will likely become more commonplace, especially in light of the study. It could take some time, however, because the units cost up to $450,000 and are several times more expensive than conventional film machines.

"Women are going to want digital," he said. "The institutions are going to have to decide now to pour some money into mammography and buy the digital units."

According to Poller, Allegheny General, Magee-Womens Hospital and St. Clair Hospital have digital mammography units.

Robert Smith, director of cancer screening for the American Cancer Society, issued a statement emphasizing the importance of regular screening.

"Younger women and women with denser breasts should not forego their regular mammogram if digital mammography is not available," he said. "While this study showed an advantage with digital imaging in these groups, it should be remembered that traditional film mammography also is effective."

The earlier a breast cancer is caught, the more likely it is to be cured, Poller said.

Researchers will continue to follow the 335 women in the study who were diagnosed with breast cancer to see whether having digital mammography leads to improved survival rates.