Authors of Nordic mammo study no strangers to controversy

The debate over mammography got hotter last month with the publication of a study by Nordic researchers claiming there's no evidence that mammography screening reduces death rates. Some mammography advocates have taken issue with what they say is an antiscreening bias on the part of the research group.

Last month's study, published online March 24 in the British Medical Journal, is only the latest salvo questioning mammography's benefits from a group headed by Dr. Peter Gøtzsche of the Nordic Cochrane Centre in Copenhagen and colleagues from the Norwegian Institute of Public Health in Oslo.

In the new study, the group said reductions in breast cancer death rates in regions with screening were the same or actually smaller than in areas where no women were screened.

'Crude and insensitive?'

But the study obscures whatever benefit mammography might have because of its "crude and insensitive" methodology, according to a response submitted by Robert Smith, Ph.D., director of cancer screening at the American Cancer Society (ACS), and Dr. Stephen Duffy, professor of cancer screening at the Cancer Research U.K. Centre for Epidemiology, Mathematics, and Statistics in London. The response was published March 30 on the BMJ Web site.

"While we expect to see a range of benefits from mammography ... to argue that there is no benefit from modern mammography on the basis of such flawed methods means this paper feeds the media's hunger for controversy but contributes nothing of substance to the evidence or the ongoing debate," Smith and Duffy wrote.

Last month's research is only the latest antiscreening message from Gøtzsche's group, which has been producing papers questioning mammography's value for the past decade. For example, in a 2008 study, Dr. Per-Henrik Zahl, Ph.D., co-author on last month's BMJ study, published research claiming that many breast cancers would "spontaneously disappear" if not detected.

But the arguments Gøtzsche and Zahl offer are not scientifically justified, according to Dr. Daniel Kopans, professor of radiology at Harvard Medical School in Boston.

"[Gøtzsche and his colleagues] keep getting things published that don't have scientific structure to them," Kopans told AuntMinnie.com. "To take two different populations that aren't uniform and compare them doesn't work."

Kopans also posted a formal response to the study on the BMJ Web site. He wrote: "There is, clearly, a major problem with the peer review with regard to screening mammography. ... The recent article in the British Medical Journal by Jørgensen et al is another example of the failure of peer review that permitted the publication of a methodologically unsupportable analysis."

Indeed, just a week later, a U.K. study again confirmed screening mammography's value, finding that regular mammographic screening for breast cancer saves the lives of two women for every one who is given unnecessary treatment. The study, conducted by Dr. Stephen Duffy and colleagues, was published online March 31 in the Journal of Medical Screening.

Long-term skepticism

Gøtzsche's work has met with skepticism for years:

• In 2000, Gøtzsche and Dr. Ole Olsen published a paper in The Lancet reporting that mammography screening is not justified (January 8, 2000, Vol. 355:9198, pp. 129-134). In response, Colin Begg, Ph.D., of the Memorial Sloan-Kettering Cancer Center in New York City called into question the publication process for the article.

  Begg wrote in The Oncologist that the "study was sponsored by the Cochrane Collaboration, but it transpires that other members of the Cochrane Breast Cancer Group had disagreed with the conclusions published in The Lancet. Subsequently, The Lancet took the extremely unusual step of essentially republishing the study, this time only displaying the results from the two trials that showed no benefit for mammography" (The Oncologist, June 2002, Vol. 7:3, pp. 174-176).