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Study finds new benefits from mammography

If the devastating Southeast Asian tsunami hadn't taken over the headlines in late December and early January, the results of a Dartmouth study of mammography might have gotten more press.

The investigation, led by cancer surgeon Richard Barth, M.D., and published in the January issue of the American Journal of Roentgenology, confirmed that mammograms are better than physical examinations at detecting breast cancers early and that tumors found by mammography are smaller and less likely to have metastasized. That finding is not surprising, since the benefits of regular mammography—especially for women aged 50 to 69—have long been known. But the study also determined that these smaller cancers are usually treated less aggressively.

Link: "We were one of the first studies to actually link mammography to breast-cancer treatment," says one of Barth's coauthors, Patricia Carney, Ph.D. The finding may still attract attention in the medical community, but Barth had hoped it would get coverage in the lay press as well—and it likely would have if it hadn't been for the timing.

Aggressive surgical treatment of larger tumors can mean breast removal as opposed to more conservative surgery. Chemotherapy is also part of aggressive management of advanced breast cancers, except in very elderly patients or those with other serious diseases. Even in young, otherwise healthy patients, chemotherapy's side effects—which occur in a high proportion of patients—include hair loss, nausea and vomiting, increased susceptibility to infections, and memory deficits.

Less toxic: "The take-home message is that there can be benefits other than just a survival benefit from having your breast cancer detected early by using mammography," says Barth. "These benefits are that if you're unlucky enough to get the breast cancer, you can have it treated with less toxic therapy. This applies to women across the entire spectrum . . . women of any age who are going to develop breast cancer."

Barth and his colleagues did a retrospective study of 992 patients with invasive breast cancer who were treated at DHMC over an 11-year period. (In a retrospective study, researchers examine patients' medical records, looking at what actually happened.)

The breast cancer was detected by physical examination in 532 of the women and by mammography in 460. The tumors detected by mammography were half the size of those found by physical examination (1.5 centimeters, compared to 2.9 centimeters) and were less likely to have metastasized to the lymph nodes. In addition, patients in the mammography group were much more likely to have undergone breast-conserving surgery, such as lumpectomy, and less likely to have had chemotherapy.

Benefits: In addition, the study identified benefits to mammography for both younger and older women. Experts have long debated whether mammography improves survival for women under 50 or over 70, but Barth's study showed that regular screenings help women in these age categories, too. For women who were 40 to 49 years old, their chance of receiving chemotherapy more than doubled if the tumor was discovered by physical examination instead of by mammography. And women 70 and older were five times as likely to undergo a mastectomy and four times as likely to receive chemotherapy if their tumor was discovered by physical exam.

"To me, the nice thing about this paper is that it shows that breast cancers detected by mammography are also less likely to result in mastectomy [and] less likely to result in toxic treatment," says Carney.

It was Barth's years of caring for women who discovered their cancers too late to take advantage of less aggressive treatments that led him to do this study. "When you see a bunch of people with advanced breast cancer, and you have to take care of them day in and day out, all week long, it's so obvious that detecting these cancers earlier is better," he says. "The really frustrating thing is to get people who haven't been screened and come in with really big cancers. . . . They all have to get really aggressive treatment in an attempt to save them."

Though experts debate optimal screening rates generally, there's no question in Barth's mind how he'd advise women about breast cancer screenings: "Start annual mammography when you are 40, and continue for the rest of your life." But, he adds, physical examination— by a caregiver or self-administered— shouldn't be stopped. It does no harm and can detect tumors, albeit not as early as mammography.

—Roger P. Smith, Ph.D.

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