Can Some Breast Cancer Tumors Regress if Left Untreated?

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By Kate Stinchfield

Do more frequent mammograms pick up some breast cancer tumors that might have gone away without treatment? Possibly, according to a controversial study published this week in Archives of Internal Medicine. However, experts caution that the research raises an interesting question, but can’t definitively answer it.

In the study, a research team led by Per-Henrik Zahl, MD, of the Norwegian Institute of Public Health, looked at two groups of women from before and after Norway stepped up its mammogram screening program in 1996.

One group of 119,000 women ages 50 to 64 had mammograms every two years, for a total of three mammograms between 1996 and 2001. The researchers compared them to a second group of nearly 110,000 women who were ages 50 to 64 in 1992 but didn’t have routine mammograms. Those women had a single mammogram in 1997.

Not surprisingly, the women who had more mammograms had more cases of invasive breast cancer—if you look for cancer, you tend to find it. However, at the end of the six-year period, cases of invasive breast cancer were still 22% higher among regularly screened women, although the researchers expected the same number of cases in both groups.

They suggest that some of the tumors detected by mammography would have spontaneously regressed had they not been caught and treated.

It’s a controversial idea, but one worth considering, says Robert M. Kaplan, PhD, the chairman at UCLA’s Department of Health Services, who cowrote an editorial accompanying the study. “Our tendency was to dismiss it when we first read it, but the more we looked at it, the more we thought that maybe there is something to this.”

Next: In rare cases, breast cancers have been known to regress

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