Right now, doctors have no way of predicting which cases of DCIS will progress. So women usually receive treatment -- which may mean surgery to remove some breast tissue or the whole breast. And that's raised concerns about overtreatment.
Because the two new studies were presented at a meeting, the findings should be considered preliminary until they have been published in a peer-reviewed medical journal.
They were also conducted by radiologists -- the specialists who do all those mammograms. But an expert who is not a radiologist and not connected to the research agreed that the findings support advice for women to begin mammograms at age 40.
"I think this reinforces concerns a lot of us have had since the [USPSTF] guidelines came out," said Dr. Therese Bevers, a professor of clinical cancer prevention at the University of Texas M.D. Anderson Cancer Center in Houston.
"There are harms from screening, and I think that's something everyone in this field recognizes," Bevers said.
But she thinks the benefits outweigh the downsides, and she also noted that the task force suggests that screening decisions be individualized for women in their 40s, taking into account their risk factors.
However, researchers are still trying to figure out what the risk factors are. Strong family history is one; but in Arleo's study, Bevers noted, only three of the 39 breast cancer patients in their 40s had a mother or sister diagnosed with early breast cancer.
"Until we have a better understanding of how to target screening to certain women in their 40s, I think we should screen everyone," Bevers said.
According to the U.S. National Cancer Institute, the average 40-year-old woman has a one in 69 chance of developing breast cancer in the next 10 years. A 60-year-old woman has a one in 29 chance.
Learn more about breast cancer and mammograms from the U.S. National Cancer Institute.
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