Articles

The major mammography study no one knows about

WRITTEN BY DAVID HODGES ON DECEMBER 8, 2011 FOR THE MEDICAL POST CHICAGO

There has been another salvo in the heated debate surrounding controversial breast cancer screening recommendations by the Canadian Task Force on Preventive Health Care (CTFPHC). New data presented at the Radiological Society of North America (RSNA) meeting here suggest that women in their 40s with no family history of breast cancer are just as likely to develop invasive breast cancer as women with a family history of the disease.

Radiologists who performed the study concluded this age group should be screened annually with mammography.
But for Toronto’s Dr. Steven Narod, the most cited scientist in the world in the field of breast cancer, the biggest story in the current breast cancer screening furor isn’t the CTFPHC’s new screening recommendations, nor is it the RSNA study, which he dismissed. It’s a Swedish study that was published in the November issue of Lancet Oncology (and first available online Oct. 12) that found most screen-detected invasive breast cancers will naturally go away on their own!

For Dr. Narod, a Tier I Canada Research Chair in breast cancer, this study handily puts the mammography debate to rest. The problem, he says, is no one is paying attention to it.

‘Front-page’ news

“The critical issue in the paradigm is not about technology, it’s not about costs and it’s not about side-effects,” Dr. Narod said. “It’s that we have intriguing evidence that many mammogram-detected breast cancers that are not palpable look like they would go away by themselves. And I think the best evidence is that Swedish paper. I believed this for a long time but these guys really put this on the line. That’s a paper that was worth being on the front page of the newspapers in the world.

“The most important question in the (mammography) debate is: How the hell do breast cancers go away by themselves? And once we accept the fact that they do, that the smaller they are the more likely they are (to go away), there’s a tremendous amount we can do and we can actually take a good approach to cancer prevention.”

The CTFPHC’s recommendations suggest average-risk women not start mammography screening until age 50, and afterward in two- to three-year intervals. Even more stringent than similar guidelines the U.S. Preventive Services Task Force issued in 2009, the guidelines have created an international media stir.

‘This is insane’

Most notably, in an article in the Globe and Mail, Toronto’s Dr. Martin Yaffe, a senior scientist in the imaging research program at Sunnybrook Health Sciences Centre, said the new Canadian recommendations leave women in their 40s “with nothing, effectively telling them to wait until a cancer becomes advanced before seeking attention. Based on the science, this is insane.”
In opposition, Dr. Cornelia Baines, professor emerita at the Dalla Lana School of Public Health at the University of Toronto, told the Globe she supports the evidence behind the guidelines, citing a host of reasons for their dismissal from “ignored conflicts of interest” to politicians who “loathe to provoke the ladies with pink ribbons.”

Medical organizations are equally divided. The Canadian Association of Radiologists (CAR) has publicly thrown its support behind breast cancer screening for women in their 40s and opposes the task force recommendations, while the College of Family Physicians of Canada endorses them.

Not surprisingly, other international groups have taken similarly different stands on early screening recommendations. For instance, like the CAR, the RSNA (along with other U.S. groups such as the American Cancer Society and the American College of Obstetricians and Gynecologists) defends screening for women in their 40s. And at the RSNA’s annual meeting, the organization highlighted a large single-centre trial in support of this during one of its premier news conferences.
The retrospective review aimed to identify the number and type of cancers diagnosed among women between the ages of 40 and 49—with and without a family history of breast cancer—who underwent screening mammography at Elizabeth Wende Breast Care in Rochester, N.Y., from 2000 to 2010. The researchers then compared the number of cancers, incidence of invasive disease and lymph node metastases between the two groups. Dr. Stamatia Destounis, a radiologist and managing partner of Elizabeth Wende, led the study.

Her findings showed that 373 of the 1,071 patients identified were diagnosed as a result of screening. Of that 373, 39% had a family history of breast cancer; 63.2% of these patients had invasive disease and 36.8% had noninvasive disease. In the no family history group, 64% of the patients had invasive disease and 36% had noninvasive disease. The respective lymph node metastatic rates were 31% and 29%. Dr. Destounis told reporters her results underscore the importance of early detection and annual screening mammography for women between the ages of 40 and 49, regardless of family history of breast cancer.
After reviewing Dr. Destounis’s study abstract (a full paper hasn’t been published), Dr. Narod said there is nothing in it to support the researchers’ conclusion.

‘It’s nonsense’

“Family history doesn’t predict breast cancer in women from age 40 to 49? That’s absolutely not true. And they certainly didn’t address the question with the study design that I read. I can’t make anything out of this study. It’s nonsense. Quote me on that.It’s bullshit.”

Dr. Narod said he supports the CTFPHC recommendations, but he doesn’t think the right issues are being discussed.
“I’m kind of amazed that everybody got it wrong on both sides of the argument, in my opinion. . . . I think mammography fails because the vast majority of breast cancers that are detected when they’re small, node negative and, mammographically, when they’re seen by a mammogram but are not palpable, go away by themselves. . . . And there’s very, very good evidence to support this.”

The proof, he said, is the aforementioned Swedish study by Dr. Per-Henrik Zahl and colleagues at the Norwegian Institute of Public Health in Oslo. Researchers compared cumulative breast cancer incidence in age-matched cohorts of women living in seven Swedish counties before and after the initiation of public mammography screening between 1986 and 1990.

The researchers invited women in their 40s to have screening every year and women ages 50 to 74 years every two years. They followed up a screened group including all women ages 40 to 69 years (328,927 subjects) for six years after the first invitation to the program. They also followed up a control group including all women in the same age range (317,404 women) for six years—four years without screening and two years when they entered the screening program. They obtained counts of incident invasive breast cancers from the Swedish Cancer Registry, with in-situ cancers excluded.

The researchers found that before the age-matched controls were invited to be screened at the end of their followup period, the four-year cumulative incidence of invasive breast cancer was significantly higher in the screened group (982 per 100,000) than it was in the control group (658 per 100,000). Even after prevalence screening in the control group, the screened group had higher six-year cumulative incidence of invasive breast cancer (1,443 per 100,000 versus 1,269 per 100,000).

The researchers indicated that “because the cumulative incidence among controls did not reach that of the screened group, we believe that many invasive breast cancers detected by repeated mammography screening do not persist to be detected by screening at the end of six years, suggesting that the natural course of many of the screen-detected invasive breast cancers is to spontaneously regress.”

“In other words,” Dr. Narod said of the finding, “there was strong evidence those cancers would have gone away by themselves. How many? Most of them. . . . Now, not every breast cancer goes away by itself . . . Breast cancers that are 2 cm and are non-palpable probably have a 10% chance of going away by themselves; 90% of them will become real cancers. A 1 cm cancer has a 50% chance of going away by itself. And one that’s 1 mm probably has a 99% chance of going away by itself. So why would we go for identifying 1 mm breast cancers?”

Articles

The major mammography study no one knows about

Comments