FRIDAY, May 16 (HealthDay News) -- After years of declining rates, the number of mastectomies performed on women with breast cancer is on the rise again, the Mayo Clinic now reports.

The increase coincided with heavier usage of magnetic resonance imaging (MRI) before surgery, according to the authors, who were expected to present their findings May 31 at the American Society of Clinical Oncology (ASCO) annual meeting, in Chicago.

Guidelines introduced in 1990 pronouncing that lumpectomy was equally effective as mastectomy for overall survival in women with early-stage breast cancer resulted in a rise in lumpectomies, also known as breast-conserving surgery, along with a decline in the number of mastectomies performed.

"But in the last 10 years, more changes have occurred in the preoperative work-up of breast cancer, and some of the changes have included the introduction of new imaging modalities such as MRI," senior study author Dr. Matthew Goetz, an assistant professor of oncology at the Mayo Clinic in Rochester, Minn., said during a May 15 teleconference. "There are also improved breast reconstruction options, as well as the introduction of genetic testing."

Previously published trials have shown that mastectomy rates may be increasing in general in the United States, Dr. Julie Gralow, an associate professor of medical oncology at the University of Washington, Seattle, added at the same news conference.

Dr. Richard J. Bleicher, co-director of the Breast Fellowship Program at Fox Chase Cancer Center in Philadelphia, confirmed this. "This is a real finding. This is not something that is isolated to Mayo. We see the same thing," he said.

Breast MRIs may detect cancer in more than one part of the breast, which, in turn, may prompt surgeons and patients to choose mastectomy over lumpectomy. MRIs also pick up noncancerous masses, which leads women to choose a mastectomy, even though the lesion doesn't need to be removed immediately.

The new research involved more than 5,000 patients with early-stage breast cancer who underwent surgery between 1997 and 2006. Information on whether an MRI was performed before surgery became available in Mayo Clinic records, starting in 2003.

In 1997, the mastectomy rate was 44 percent. That number declined to 30 percent in 2003, then rose again from 2004 to 2006, to 43 percent.

"That's similar to the rate seen in the late 1990s," Goetz said.

In 2003, 11 percent of women underwent MRI before their surgery; by 2006, that number had risen to 23 percent.

Fifty-two percent of all patients receiving MRI had a mastectomy, versus 38 percent of women who did not have an MRI.

Mastectomy rates in women who did not have an MRI also increased, from 28 percent in 2003 to 41 percent in 2006.

Nevertheless, Goetz said, "patients who had preoperative MRI were significantly more likely to undergo mastectomy."

But the greater sensitivity of MRI may, in fact, be a double-edged sword.

"Although there has been a lot of excitement about the sensitivity of MRI, there is a significant downside. We don't have evidence that MRI improves our outcome. What we do know is that it finds a lot of things that we don't know the significance of, and many aren't significant," Bleicher.

He added, "I would say this data is phenomenally important, because we're starting to take a step back about the excitement of MRI and look at it through more realistic non-rose-colored glasses."

"Future studies are needed to determine those factors most likely to influence changes in surgical management and whether the changes influence breast cancer outcomes or quality of life," Goetz said.

More information

The National Cancer Institute has more on surgery options for breast cancer patients.

SOURCES: Richard J. Bleicher, M.D., co-director, Breast Fellowship Program, Fox Chase Cancer Center, Philadelphia; May 15, 2008, teleconference with Matthew Goetz, M.D., assistant professor, oncology, Mayo Clinic, Rochester, Minn., and Julie Gralow, M.D., associate professor, medical oncology, University of Washington School of Medicine, Seattle; May 31, 2008, presentation, American Society of Clinical Oncology, annual meeting, Chicago

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