One in five breast cancer tumors may regress without treatment, a new study suggests. Researchers screening women who had a history of regular mammograms and those who did not report that those in the first group were diagnosed with 22 percent more breast cancers, implying that such a percentage of cancers would have eventually gone away on their own. The study opens up a controversial debate on whether early and aggressive treatment of breast cancer is always the best procedure. But many experts are wary of the new findings, saying the conclusions were incorrectly drawn and fearing they will discourage women from getting mammograms.
"The idea that somehow these cancers go away entirely is, I would say, an intriguing hypothesis, but one we don't have a lot of evidence to support," [Reuters]
said Dr. Eric Winer. Researchers in Norway followed two groups of women, each numbering more than 100,000, for six years. The first group, monitored from 1992 to 1997, did not receive mammograms until the end of the study. (Mammograms were not common in Norway until 1996.) The second group, monitored from 1996 to 2001, received mammograms every two years.
For every 100,000 women who were screened regularly, 1,909 were diagnosed with invasive breast cancer over six years, compared with 1,564 women who did not have regular screening [New York Times]—a difference of 22 percent. The researchers attribute this difference to the number of undetected tumors in the first group that vanished on their own during those six years.
There is currently little understanding of how cancer tumors can spontaneously regress. Reported cases usually involve neuroblastomas, a rare cancer that afflicts children, and most are seen as medical mysteries. The researchers cite 32 known cases of breast cancer tumors that regressed without treatment, a small number compared to the 180,000 cases of breast cancer diagnosed annually in the U.S. alone.
At the moment, the finding has no practical applications because no one knows whether a detected cancer will disappear or continue to spread or kill [New York Times].
However, Robert M. Kaplan, who wrote an editorial [subscription required] accompanying the new study in the Annals of Internal Medicine, says if the results can be replicated,
it could eventually be possible for some women to opt for so-called watchful waiting, monitoring a tumor in their breast to see whether it grows. “People have never thought that way about breast cancer,” he added [New York Times]. Such a paradigm shift could decrease the number of biopsies for noncancerous lumps, an inevitable consequence of regular screenings.
But others warn that eschewing regular screenings would be irresponsible and potentially deadly. The American Cancer Society recommends annual mammograms for most women over the age of 40. Robert A. Smith, head of cancer screening for the Society believes strongly that the researchers are wrong in their conclusions. There are many factors that could have caused the difference in breast cancer incidence—for example, he suggests, the women who did not receive regular treatments could in fact have tumors that were not detected by the single mammogram at the end of the study.
Considering the prevalence of breast cancer, Smith says that doctors would surely have noticed if these tumors were really disappearing. "It's important that people not wonder if women lost their breasts for no reason," Smith says. "That's a reprehensible conjecture" [USA Today].
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