Why does breast cancer screening (search) fail?

Blame missed mammograms (search) — and mammograms that don't detect early breast cancers, a new study suggests.

Screening for breast cancer means regular mammograms. Experts disagree about who should get mammograms and how often they should get them. But most U.S. breast cancer experts agree that women over 50 die of breast cancer at least 30 percent less often if they get regular mammograms.

Most health plans pay for — and actively promote — regular mammograms. But even women with very good health insurance still show up in doctors' offices with advanced, late-stage breast cancer. Why weren't these breast cancers found earlier when they were easier to treat?

That's what Stephen H. Taplin, MD, and colleagues wanted to know. So Taplin, now a senior scientist at the National Cancer Institute (NCI), led a study that analyzed data on 1.5 million women enrolled in seven major health-care plans. They compared 1,347 women with late-stage breast cancers with 1,347 similar women with early-stage breast cancers.

The results surprised Taplin.

"At first we thought we were losing people in the follow-up process after breast cancer detection," Taplin tells WebMD. "But we found that the problem in follow-up is relatively small. It was really screening and detection where the problems were."

The screening problem: 52 percent of women with late-stage breast cancer hadn't had a mammogram in the last one to three years.

The detection problem: Mammograms failed to find breast cancer in nearly 40 percent of the women who - in the interval between mammograms — came down with late-stage breast cancer.

The findings appear in the Oct. 20 issue of The Journal of the National Cancer Institute.

Women Who Miss Mammograms

Some women were more likely to be among those who missed mammograms:

—Women with late-stage breast cancer were nearly three times as likely to miss mammograms if they were age 75 or older.

—Women with late-stage breast cancer were 78 percent more likely to miss mammograms if they were unmarried.

—Women with late-stage breast cancer were 84 percent more likely to miss mammograms if they had no family history of breast cancer.

—Nearly 60 percent of women who missed mammograms were in lower-education groups.

—Nearly 55 percent of women who missed mammograms were in lower-income groups.

That's a clue to how health plans can do better, says study co-researcher Ann M. Geiger, PhD, group leader for cancer research at Kaiser Permanente Southern California.

"The message is out there: Women need to get screened for breast cancer. But there appears to be a group of women who either don't know they should do this or who don't pursue breast-cancer screening for some other reason," Geiger tells WebMD. "In our study, it isn't lack of insurance. But maybe it's other things, like getting yourself to the clinic on a workday, arranging for child care — things that become big problems for lower-income women."

Taplin says the problem really isn't missed mammograms. It's women who simply don't get screened for years on end.

"If you were to focus on people who have not been screened in the prior three years and just identified them, you could begin to affect late-stage disease," Taplin says. "Whether that affects mortality is unknown. We think you will have a higher chance of affecting mortality. But the issue is not so much repeat screening as it is getting people who haven't been screened."

Screening for breast cancer is not a one-way street. Yes, mammograms detect breast cancer early, when it's easier to treat. But the tests often result in biopsies that find no breast cancer, creating physical, emotional, and sometimes financial hardship.

Taplin and Geiger are quick to point out that their study does not prove mammograms save lives. It does, however, suggest that women think hard about the consequences of not having regular mammograms.

"We may tend to underestimate the difficulties that breast cancer screening makes for women," Geiger says. "But the tradeoff is ending up with a cancer that is very difficult to treat. I have a mother who has issues and has to get a mammogram every six months. It freaks me out because her chances of false positives are high and she has already had some biopsies that turned out negative. But I think the tradeoff is worth it."

It's up to every woman to decide whether to undergo breast cancer screening. As the study data suggest, it's a big decision — a decision best made with a doctor's advice.

"Women who refuse screening should have a chance to tell a doctor what their concerns are," Taplin says. "I am not saying they should be dragged by ropes and chains to be screened, but we should at least talk to them and find out what their concerns are."

Mammograms That Miss Breast Cancer

Women missing mammograms isn't the only reason breast cancer screening fails. Mammograms also sometimes miss breast cancers. A large proportion of women in the Taplin study got their diagnosis of late-stage breast cancer in between mammograms.

"Finding the cancer when it is there is a part of the problem," Taplin says. "We don't know the percentage of these late-stage cancers that were visible on the last mammogram. About a third of the time it is visible, but we don't have that data here. We need better ways of helping radiologists improve interpretation. And we need more research at NCI to find better detection methods."

Geiger agrees that there's an urgent need for better mammogram technology. In the meantime, she says, it's a good idea to improve radiologists' skill at reading mammograms.

"You could have a tumor that is not yet detectable, and it could show up in the interval before your next mammogram. There is no perfect medical test," Geiger says. "An obvious next step is to look at breast cancer detection. Kaiser Permanente Colorado has a great program looking at radiologists, providing training and specialties for mammogram readers."

By Daniel J. DeNoon, reviewed by Michael W. Smith, MD

SOURCES: Taplin, S.H. The Journal of the National Cancer Institute, Oct. 20, 2004; vol 96: pp 1518-1527. Stephen H. Taplin, MD, senior scientist, division of cancer control and population sciences, National Cancer Institute, Bethesda, Md. Ann M. Geiger, PhD, group leader for cancer research, Kaiser Permanente Southern California.