Disagreement continues to dog screening mammography

April 1, 2009

In a commentary on the mammography controversypublished in Diagnostic Imaging six and ahalf years ago,2 I discussed how two prestigiousgroups of scientists analyzed data from the eightmost commonly recognized clinical trials onscreening mammography conducted to date andarrived at opposite conclusions.

Here we go again
Here we go again and again
Wondering how it all began
Wondering will it ever end
Round and round we go
Where it's going nobody knows
Though I know we've been
This place before...
John Lennon, Phil Spector

In a commentary on the mammography controversy published in Diagnostic Imaging six and a half years ago,2 I discussed how two prestigious groups of scientists analyzed data from the eight most commonly recognized clinical trials on screening mammography conducted to date and arrived at opposite conclusions. The first group, the U.S. Preventive Services Task Force, concluded that mammographic screening to detect early breast cancer was efficacious and clearly saved lives. The second group, the Nordic Cochrane Center in Denmark, the head scientist of which is Dr. Peter Gøtzsche, concluded that mammography not only fails to reduce deaths from breast cancer but may even do more harm than good. I concluded that the mammography controversy would persist for many years and that the two sides of the story-one supportive without reservation, the other claiming that mammography is of little or no value-would continue to attract public attention.

As predicted, claims and counterclaims regarding the efficacy of mammographic screening have continued to be published in the scientific literature and have periodically captured the attention of the news media, which stories have, in turn, attracted public attention. One recent study showed that screening mammography resulted in a reduction in deaths from breast cancer of up to 44%.3 Another recent report, based on a meta-analysis of randomized controlled trials, however, concluded that the reduction of deaths due to breast cancer attributable to mammography was as low as 7%.4 One nationally known radiologist-mammographer's disagreement with the latter report was so vehement that he characterized it as “misleading and an outrage.”5

Just as the controversy over the efficacy of mammography seemed to be quieting down somewhat, in February Gøtzsche and colleagues fired a new salvo against mammography in a British Medical Journal article entitled, “Breast screening: the facts-or maybe not.”6 Gøtzsche et al strongly criticized public health officials in the U.K. for informing the British public about the benefits of screening mammography but among the harmful effects enumerated by Gøtzsche and his group were that “[t]he likelihood of women being overdiagnosed after mammography is 10 times greater than the likelihood of their avoiding death from breast cancer,” and “overdiagnosis and subsequent overtreatment of healthy women result in 30% more surgery, 20% more mastectomies, and more use of radiotherapy.”6

The Nordic scientists also pointed to mammography's high rate of false-positive diagnoses, the likelihood of which rises with each screening. The odds of a woman in the U.S. getting a false-positive result hits 50% after 10 screenings. False-positive diagnoses subject women patients to “anxiety, worry, despondency, and problems with sleeping, sexuality, and behavior.”

The Gøtzsche group then focused on carcinoma in situ, an entity that “constitutes 20% of the diagnoses made at screening in the U.K.,” leads to invasive cancer in “fewer than half the cases,” but for which “30% of patients are treated with mastectomy.” The group again emphasized that mammography screening “does not decrease total cancer mortality.”

Gøtzsche et al concluded their article by explaining that they had developed a new evidence-based leaflet that they hope will be distributed to women. Highlighted in the leaflet are admonitions such as, “If 2000 women are screened regularly for 10 years, one will benefit from screening and will avoid dying of breast cancer; at the same time 10 healthy women will, as a consequence, become cancer patients and will be treated unnecessarily. These women will have either part of their breast or the whole breast removed, and they will often receive radiotherapy, and sometimes chemotherapy. Furthermore, about 200 healthy women will experience a false alarm, the psychological strain [of which] can be severe.”

MANY DISAGREE

To be sure, many radiologists and other medical experts disagree with many if not nearly all of the Gøtzsche group's assertions. In an American Journal of Roentgenology article, also published in February, women's imaging section editor Marcia Javitt reiterated, “It is clear that screening mammography decreases breast cancer mortality in women older than 40 years and especially in those who are 50-69 years old.”7 Other researchers have reported that the reduction in mortality from breast cancer due to mammography screening ranges from 15% to 75%.8-12

Gøtzsche and colleagues touched on one other facet of the mammography controversy: a “conflict of interest when those who provide the information are responsible for the success of the screening program.” This particular concern has been voiced by others as well. One Canadian researcher has written about what he calls the “arrogance of preventive medicine, proponents of preventive medicine who are aggressively assertive, pursuing symptomless individuals and telling them what they must do to stay healthy, confident that the interventions they espouse will do more good than harm to those who accept and adhere to them.”13 Similar sentiments have been expressed by German radiologist Prof. Christiane Kuhl (who chided U.S. radiologists for being “reluctant to educate women about screening mammography for fear of reducing their participation in undergoing screening”),14 and researcher-author Dr. H. Gilbert Welch (“[w]e should talk about screening in the context of choice instead of obligation,”15 and “[t]he reality of cancer testing is that it is the downsides that are certain, while the benefits-in most cases-are unclear”16).

I do very much believe, and I think most radiologists and other medical experts believe, that radiologists, radiology organizations, and allied medical societies, including but not limited to the American Cancer Society, must fully and truthfully educate the public about the benefits, limitations, and potential downsides and risks of mammography, particularly as they relate to the diagnosis, management, and prognosis of breast cancer. Acknowledging rather than denying the existence of controversies regarding the efficacy of mammography, and expanding rather than limiting public discussion and debate of viewpoints and opinions critical of screening mammography expressed by various researchers in the scientific community, will serve the interests of both the public at large and the medical profession.

It was nearly 50 years ago that the first major randomized study evaluating the efficacy of screening mammography was conducted. The project was sponsored by the Health Insurance Plan of New York, and it found that mammography reduced the mortality rate of breast cancer in women by 30%. Since that time, at least seven other randomized studies have been conducted, the findings of which have been reported, then reviewed, then rereviewed, and again re-rereviewed by radiologists, epidemiologists, and other scientists innumerable times.

Many of the reviewers have concluded that these studies confirm that screening mammography reduces mortality from breast cancer, but many others, analyzing the same raw data, have disagreed-sometimes vehemently so. Clearly, the scientific as well as the lay literature is replete with reports from researchers who are convinced that mammography saves lives but also with articles from researchers who believe that screening mammography is not only of no value but may actually be harmful.

NO RECONCILIATION

It is natural to ask how we can reconcile the conflicting data generated and opinions expressed by myriad researchers and scientists, both within and beyond the U.S., regarding the efficacy of screening mammography. My answer is that we cannot. We must accept the reality that the mammography controversy will continue indefinitely. The fact that these periodically appearing articles concerning the efficacy of screening mammography and its effect on breast cancer deaths tend to do nothing more than reiterate opinions that have already been expressed repeatedly brings to mind the biblical book of Ecclesiastes, in which it is written that “[w]hat has been will be again, what has been done will be done again; there is nothing new under the sun.”17 When it comes to data related to mammographic screening and breast cancer, it does indeed seem that there is nothing new under the sun.

So. Is screening mammography good or bad? What should radiologists advise women? I personally believe that there is sufficient, albeit not incontrovertible, evidence that screening mammography does reduce mortality resulting from breast cancer; whether the reduction factor is 5%-or 15% or 30%-is irrelevant. Thus, I firmly believe that radiologists and other physicians should, after discussing both the pros and cons of screening, encourage, but not coerce, women over 40 to undergo annual screening mammograms. In the final analysis, however, the decision must be made by the woman herself.

I close by returning to Lennon and Spector's “Here We Go Again,” including, with apologies, my own additional lyrics: We've all heard it so many times before:
Mammography screening's a test many
praise, but some naysayers abhor;
Scientists on both sides keep finding new data that “unequivocally”
support the view
That their position on mammography
is the only one that's true;
Any side that thinks it can convert
the other shouldn't even begin,
For the opinions are so entrenched that
there's no way to win;
So when more conflicting mammographic
data appear, as they surely
will now and then,
My advice is to maintain your equanimity and simply say, “here we go again.