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Study: Some Breast Cancers May Naturally Disappear

Posted on: Tuesday, 25 November 2008, 15:25 CST

Researchers recently reported findings that show how some breast cancers that are detectable by mammograms could naturally disappear on their own.

Experts responded to the new research presented by Dr. Per-Henrik Zahl of the Norwegian Institute of Public Health in Oslo and Norwegian and U.S. colleagues by affirming that women should continue to get regular mammograms.

Researchers looked at invasive breast cancer rates among nearly 120,000 women age 50 to 64 who had a mammogram every two years over a six-year period. This group was compared to a group of women of similar age who were screened only once at the end of the six-year period.

They found 22 percent more invasive breast tumors in the group who had mammograms every two years.

Researchers say this lends credence to the theory that some cancers disappear naturally, although there is no biological reason to explain how this might be.

"We are the first ones to publish such a theory," Zahl said.

"What we say is many cancers must spontaneously disappear or regress because we cannot find them at later screenings. I have no biological explanation for this."

The American Cancer Society estimated that about 465,000 women die of breast cancer globally each year, and 1.3 million new cases are diagnosed.

"I think generally when we look at studies like this it is important to keep in mind there are some studies that change practice and others that make us think a little bit more, said Dr. Eric Winer, director of the Breast Oncology Center at Dana-Farber Cancer Institute in Boston.

"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," said Winer, who was speaking on behalf of the American Society of Clinical Oncology.

Bob Smith, director of cancer screening for the American Cancer Society, said Zahl's team misinterpreted the data, and expressed doubt about the idea that a significant number of breast tumors "spontaneously regress."

"I imagine there are still some people who believe the Earth is flat, but there are not very many of them," Smith said. "It's not usual -- it happens every day that research is published that gets it wrong."

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On the Net:

• Norwegian Institute of Public Health
• American Cancer Society

Source: redOrbit Staff & Wire Reports

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