Breast density disclosure may do more harm than good

Re: Breast density disclosure may do more harm than good by Laura Eggertson

Ms. Eggertson, in her article got a few things right, but several things wrong. She correctly communicated the double-barreled risk associated with breast density. It is important for women and their healthcare providers to know when an individual is at increased risk of developing breast cancer. It is even more important that they be informed when there is increased likelihood of an already existing cancer being missed on a mammography screen because it is hidden by dense breast tissue. A woman with breast cancer who receives false reassurance of a negative examination is at risk of delayed, and in some cases, more harmful treatment once the cancer is found.

My concerns about this article, begin with its title. Of course any activity can cause more harm than good if it is not done properly. But, why shouldn’t communication of breast density be done properly? And while the push to communicate information on density came from advocacy, there is plenty of solid and well reproduced quantitative peer-reviewed evidence to support the existence of those two risk factors.

Ms Eggertson's article states that there are no definitive studies demonstrating that giving women information on their breast density will reduce breast cancer incidence. I don’t think that anybody has suggested that this would occur. Density is associated with breast cancer risk, but reducing density doesn’t necessarily reduce risk.
The most actionable aspect of breast density is currently not its association with breast cancer risk but its use in deciding, for an individual woman, if a mammogram is or is not sufficiently accurate for her breast cancer screening. While there are quantitative computer methods for assessing density (disclosure – I developed such a program over 20 years ago), this decision can be made in a couple of seconds or less by eye by an experienced breast radiologist while looking at the mammogram. If the accuracy is likely to be compromised by density, then a woman should have the right to know this and consider alternatives.

It is this lack of accuracy combined with the inertia of both government and the medical community in Canada to act on this information that led to a grass roots group taking on an advocacy role. They followed the example of women in the US who had the similar experience of having cancers missed due their having very dense breasts, not having been advised of this risk, and thus leaving them in the dark about the potential risks to their lives

Will, as Dr. Sharon Batt, quoted in Ms. Eggertson’s article, asks, giving women with very dense breasts the opportunity to have supplemental screening save lives? Ms. Eggertson is correct when she points out that we don’t have direct randomized studies testing this, but these will probably never be conducted. Such studies are large and expensive and governments won’t fund them. But, despite the limitations of current screening that Dr. Batt mentions, many studies and overviews have clearly demonstrated that earlier detection reduces breast cancer deaths. Even the Canadian Task Force on Preventive Health Care acknowledges that early detection is life saving for women 40 and older, although they grossly underestimate the magnitude of benefit. That’s why we have had screening programs across Canada for almost 30 years. Therefore, it is logical that if screening doesn’t work as well and cancers are missed in very dense breasts there will be more deaths. If we can find those cancers more effectively in the 10-15% of women with the most dense breasts, and there is plenty of evidence that techniques like breast ultrasound and others can achieve this, we can avoid some of those deaths. Ms Eggertson's article neglected to mention that the FDA, considered by most to be an evidence-based organization, has now decided to make communication of breast density a requirement across the US.

Ms Eggertson is correct that medical guidelines for managing dense breasts are vague and they should certainly be tightened up. The vagueness may arise because the threshold between acceptability and inadequacy of current screening will always be somewhat arbitrary and there are costs, workforce and accessibility issues around the provision of supplementary screening that must be addressed by providers.

Ms Eggertson may have misinterpreted the quotation from Dr Tamimi, a highly reputable scientist. Dr Tamimi’s stated concerns are not about whether it is a good idea to communicate information on density, but that the messages have not been delivered as clearly and effectively as they should be.

The answers to those concerns appear to be quite straightforward. First, drop the paternalistic attitude about “not worrying your little head”. Then, use national guideline resources to ensure that women are effectively informed when they have dense breasts and their mammograms are likely to be less reliable. Provide them with information on possible supplemental screening, so they can make their own decisions about screening. At the same time provide their physicians with accurate information on the strengths and weaknesses of those screening tools, so that they can discuss them knowledgably with their patients. Only then can the informed decision making process advocated by the Canadian Task Force on Preventive Health Care credibly take place. Finally, convey to women how they might reduce density-associated breast cancer risk based on lifestyle factors. While the evidence is less solid that such behaviour modification will be effective, losing weight and drinking less alcohol are unlikely to do any harm.

All of this is doable today. Or we can accept the status quo and live with the consequences – more women dying of breast cancer unnecessarily.

Martin J. Yaffe, PhD, C.M., Hon. D.Sc.
Senior Scientist, Physical Sciences
Tory Family Chair in Cancer Research
Sunnybrook Research Institute
Professor, Depts. Medical Biophysics and Medical Imaging
University of Toronto

Co-Director, Imaging Research Program
Ontario Institute for Cancer Research
2075 Bayview Avenue
Rm S657
Toronto, ON, Canada M4N 3M5
Tel. 416 480-5715 martin.yaffe@sri.utoronto.ca