Study Finds Some Invasive Breast Cancer Tumors Might Regress Without Treatment

Main Category: Breast Cancer
Article Date: 26 Nov 2008 - 7:00 PDT

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A new study of breast cancer in Norwegian women suggests that some breast tumors may regress on their own over time, the New York Times reports. The study -- published Tuesday in the Archives of Internal Medicine -- followed two groups of more than 100,000 Norwegian women ages 50 to 64 for two consecutive periods: from 1992 to 1997 and from 1996 to 2001. Norway initiated mammography screening in 1996 (Kolata, New York Times, 11/25). Researchers compared invasive breast cancer rates among the first group -- who received just one screening at the end of the time period -- with rates among the second group, who were screened every two years (Kahn, Reuters, 11/25). They found that women who had regular mammograms had 22% more cancers than women who did not have regular mammograms. Overall, there were 1,909 diagnoses of invasive breast cancer for every 100,000 women who were screened regularly, compared with 1,564 diagnoses for every 100,000 women who were not screened regularly. According to the Times, the study suggests that invasive breast cancers might disappear without treatment "in larger numbers than anyone ever believed." However, the finding currently "has no practical applications because no one knows whether a detected cancer will disappear or continue to spread or kill," the Times reports. The study was conducted by Gilbert Welch of VA Outcomes Group, Per-Henrik Zahl of the Norwegian Institute of Public Health and Jan Maehlen of Ulleval University Hospital in Oslo (New York Times, 11/25). According to the authors, "Our findings simply provide new insight on what is arguably the major harm associated with mammographic screening, namely, the detection and treatment of cancers that would otherwise regress" (Cortez, Bloomberg/Philadelphia Inquirer, 11/25).

Welch said the most likely explanation for the findings is that "there are some women who had cancer at one point and who later don't have that cancer." Two possible alternative explanations are that women who had regular scans used hormone therapy to relieve menopausal symptoms, while the other women did not, or that mammograms' ability to detect more tumors improved over the six-year period, the Times reports. However, researchers calculated that hormone use could account for no more than 3% of the effect, and mammography's sensitivity did not appear to change.

In an accompanying editorial, Robert Kaplan of the School of Public Health at the University of California-Los Angeles and Franz Porzsol of the University of Ulm wrote, "If the spontaneous remission hypothesis is credible, it should cause a major re-evaluation in the approach to breast cancer research and treatment" (New York Times, 11/25). The editorial also said that if the hypothesis of natural regression is correct, then 20% of women who received a biannual mammogram were treated unnecessarily (Bloomberg/Philadelphia Inquirer, 11/25).

According to the Times, "some experts remain unconvinced" (New York Times, 11/25). Eric Winer of the American Society of Clinical Oncology said, "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, 11/25). Robert Smith, director of cancer screening at the American Cancer Society, said, "The conclusion that more than one in five invasive breast cancers is destined to regress without incident if not detected by mammography is nothing more than an overreaching leap in logic." He added that the excess cancers found in the study were a reflection of the additional cancers detected through mammograms that otherwise likely would have gone unnoticed for years (Bloomberg/Philadelphia Inquirer, 11/25). ACS recommends women undergo an annual mammogram beginning at age 40 (Szabo, USA Today, 11/25). However, Suzanne Fletcher of Harvard Medical School said, "The issue is the unintended consequences that can come with our screening. In general we tend to underplay them." She said the new findings are "part of the picture" of cancer screening (New York Times, 11/25).

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