Breast Cancer Milder If Caught by Mammogram

Lower Risk Seen for Mammogram-Detected Breast Tumors

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Aug. 31, 2004 -- There's consolation for women who, during regular breast cancer screening, find out they have a tumor. Outcomes are significantly better when mammograms are the first sign of breast cancer.

The finding comes from analysis of detailed medical records from nearly 3,500 Finnish women diagnosed in 1991-1992 with invasive breast cancer. It suggests that women with mammogram-detected breast cancer may not need as aggressive treatment as women whose tumors are found in other ways, says Heikki Joensuu, MD, director of oncology at Helsinki University Central Hospital in Finland.

"This study certainly does not prove the value of screening," Joensuu tells WebMD. "It just tells us that tumors found in screening mammograms are different than the ones found outside screening. These tumors may be in less need of aggressive systemic therapies."

When doctors find a treatable breast cancer, they almost always remove it. If breast-conserving surgery is possible, most doctors follow up with radiation therapy. Women whose cancers are sensitive to hormones also get drugs that keep estrogen out of cells or that reduce estrogen levels. Women may also receive chemotherapy.


Because aggressive cancer therapies have serious side effects, doctors are always looking for ways to identify patients who will do well without such treatments. Now mammograms may offer a new clue.

It is, however, no more than a clue at this time. The findings aren't going to make any immediate change in breast cancer treatment, says Otis Brawley, MD, associate director for cancer control and chief of the solid tumor service at Emory University's Winship Cancer Institute in Atlanta.

"This changes nothing about any current treatment recommendations: Women should get screened, and if breast cancer is detected they should get treated," Brawley tells WebMD. "But in 10 or 15 years, we may say, 'Ms. Jones, you have a breast cancer that does not need to be treated. Ms. Smith, your breast cancer needs treatment, but not very aggressive treatment. Ms. Williams, you need aggressive treatment.' We are going to be tailoring treatment to patients with much better knowledge than we currently have."

Not Just a Matter of Size

It's common wisdom that regular mammogram screenings catch tumors while they're still small. Early cancer treatment, of course, tends to be more successful than later treatment. But even when they have cancers of the same size, the Finnish study shows, women with mammogram-detected breast cancer do better than those who find they have breast cancer in other ways.

Joensuu and colleagues looked at medical records for nearly 3,000 women with breast cancer -- about half of all breast cancers diagnosed in Finland during 1991-1992. They didn't look at whether women got regular mammograms or not (although the vast majority did). They just looked at whether or not the women's cancers were found during a mammogram.

Even after matching patients for tumor size, lymph-node cancer spread, age, and tumor cell type, women whose cancers were found during mammograms had significantly better 10 year, disease-free survival and less spread of their breast cancer to distant body sites.

That's a lot better than studies that show the natural progression of breast cancer would suggest, notes Ruth M. O'Regan, MD, of Emory University's Winship Cancer Center, in an editorial accompanying the study. Both articles appear in the Sept. 1 issue of The Journal of the American Medical Association.


"These data suggest that mammography screening may be more than a useful, acceptable screening tool - it may actually select for patients with a favorable prognosis," O'Regan writes.

What's going on? The study doesn't answer this question, but Joensuu thinks it may be that mammograms find lazier, less aggressive tumors.

"In my mind it makes sense that cancers in which the woman has no symptoms may be different from symptomatic cancers," he says. "Women with symptomatic breast cancer may feel pain or tenderness or pressure in their breast, or they may have a nipple discharge. Possibly these symptoms are related to some cancer invasiveness factors. For example, the pain might be due to the tumor invading or giving off chemicals that disturb the nerves. The nipple discharge may be caused by invasion of tumor cells into the ductal system. So these may be more invasive than asymptomatic cancers. We lack good analytical methods for studying this, but that is my best guess."

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SOURCES: Joensuu, H. The Journal of the American Medical Association, Sept. 1, 2004; vol 292: pp 1064-1073. O'Regan, R. The Journal of the American Medical Association, Sept. 1, 2004; vol 292: pp 1062-1063. Heikki Joensuu, MD, head of oncology division and medical director, Helsinki University Central Hospital, Helsinki, Finland. Otis Brawley, MD, professor of epidemiology, Rollins School of Public Health; associate director for cancer control and chief of the solid tumor service, Winship Cancer Institute, Emory University, Atlanta.
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