The Collateral Damage of Being at Average Risk of Breast Cancer and Having Dense Breasts

A woman cannot participate in shared decision making about her values and preferences of screening without weighing the pros and cons of over-diagnosis, false positives and missed positives.
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"The main goal of mammographic screening is to reduce breast cancer mortality by reducing the incidence rate of advanced breast cancer. Thus the aim of screening mammography is to detect breast cancer early in its natural history." These two sentences, included in preamble to the JAMA article introducing the American Cancer Society (ACS) Guidelines for average-risk women, assert the fundamental purpose as to why women participate in mammographic screening.

Buried in the preamble to the guidelines is the critical breast health issue of dense breast tissue. The publication concludes that "there are also women outside of these risk categories who are still at higher than average risk of breast cancer for whom mammography alone may be less effective... including women with significant mammographic breast density."

Twenty-four states have enacted density reporting legislation, beginning in my state of Connecticut in 2009. The intent of the legislation is to give the consumer/patient the facts about the impact of dense breast tissue on mammographic screening. A concluding statement in the JAMA guideline article states, "The ACS also recommends that women be provided with information about risk factors, risk reduction, and the benefits, limitations and harms associated with mammographic screening." The potential harm of missed, delayed and advanced breast cancer, because of the masking of dense breast tissue, must be disclosed to women, regardless of what state she resides in or whether she is of average, intermediate or high risk of breast cancer.

More than 75 percent of women diagnosed with breast cancer are women at average risk of the disease. All too often, health care providers write off the issue of dense breast tissue and screening beyond the mammogram in discussions with these average-risk women, dismissing the masking effect of dense breast tissue. The masking of dense tissue, resulting in a missed positive cancer, seldom receives the interest as the harms of a false positive. Where physicians and researchers are quoted in the JAMA article as being concerned with false positives, there are no guidelines to protect average risk women with dense breast tissue from the harms of false negatives.

Discussing patient risk factors are critical components when determining a woman's personal screening surveillance, including adjunct technology to mammography and screening intervals. While a high-risk woman has a greater likelihood of having a breast cancer diagnosis than an average-risk women, both are at risk of having their cancer masked by mammography. This is why an MRI, a very sensitive technology for detecting breast cancer, is recommended as an adjunct to mammography for women with a 20 percent life-time risk of breast cancer.

Women with extremely dense breast tissue have a 17x greater likelihood of having an interval cancer than women with fatty breasts. Interval cancers are defined as a cancer that is detected within one year of a negative mammogram and are often more advanced than screen detected cancer. The mortality reduction benefit of early detection by mammography and, in turn, quality of life benefits often do not apply to women with dense breast tissue because mammography alone may be less effective. This is the collateral damage of being an average-risk woman with dense breast tissue.

The stories on of average-risk women, who never missed a mammography appointment resulting in advanced disease and, for some, death, might be looked upon and dismissed as anecdotal evidence. However, more than two decades of science refute that claim. The main goal of mammographic screening is to reduce advanced disease, as stated in the ACS guidelines. Giving women at average risk with dense breast tissue access to screening beyond the mammogram is essential to further that goal.

The ACS Guideline Development Group used observational studies to estimate benefits and harms of screening, stating that "well-designed observational studies produce results that are qualitatively consistent with the majority of the RCTs." There are multiple technologies available now that have been the focus of observational studies that demonstrate an improvement in the performance of screening beyond the mammogram.

Renowned radiologist Lazlo Tabar and others, including ACS Epidemiologist, Robert Smith, authored a recent publication in the Breast Journal concluding that an indicator of the impact of a screening program is the incidence of the reduction of advanced disease. Breast cancer screening programs must embrace tailored imaging to provide all women with the greatest opportunity to reduce this risk of an advanced cancer. The authors point to breast density reporting laws, leading to opportunities for more sensitive screening, to decrease the incidence rate of advanced breast cancer.

The JAMA preamble to the guidelines also reports that ACS plans to update its screening recommendations to include additional evidence on factors associated with increased risk (including breast density) and screening outcomes and update its screening recommendations for women at increased and high risk. This is welcomed news for the average-risk woman with breast density.

A woman cannot participate in shared decision making about her values and preferences of screening without weighing the pros and cons of over-diagnosis, false positives and missed positives. While anticipating the ACS future update on screening recommendations, including breast density, health care providers would best serve women, who fall within the new ACS average-risk guidelines, by including discussions about the impact of dense breast tissue on mammography screening sooner than later.