Breast Density Knowledge and Awareness

Abstract

Objectives: We reviewed the literature on breast density knowledge and breast density awareness to explore what challenges are faced by this area of research. Method: A review of PubMED, PsycINFO, and CINAHL databases was performed. Studies were published in peer-reviewed journals (in all years available) and written in English. The broad search terms used were [“breast density”] AND [“knowledge” OR “awareness”]. Eligible articles were included in the final analysis after meeting the following inclusion criteria: (1) the records had to quantitatively examine and report breast density knowledge and awareness, (2) the number of participants in the sample had to be clearly specified, and (3) studies reporting differences in breast density knowledge and awareness between racial and ethnic groups were included in the review. Results: Of the 277 articles identified, only 5 met inclusion criteria and addressed breast density knowledge and awareness. Characteristics of studies and results were examined. Conclusions: There is insufficient evidence to determine a pattern of breast density knowledge and awareness in women. More quality studies are needed that focus on how well women understand the relationship between breast density, breast cancer risk, and breast cancer screening, especially in diverse populations.

Breast density (BD) is a measure of the extent of radiodense fibroglandular tissue in the breast. The American College of Radiology uses 4 breast composition categories defined by the visually estimated content of fibroglandular density tissue within the breasts to classify BD: The breasts are almost entirely fatty; there are scattered areas of fibroglandular density; the breasts are heterogeneously dense, which may obscure small masses; and the breasts are extremely dense, which lowers the sensitivity of mammography.¹ It has been reported that about 50% of women between the ages of 40 to 74 years have dense breasts.² A meta-analysis of BD literature identified BD as a strong risk factor for breast cancer.³ Relative to those with scattered fibroglandular densities, women with extreme density had an increased risk for breast cancer (odds ratio [OR] = 1.77, 95% confidence interval [CI] = 1.38-2.26), while those with low density had reduced risk (OR = 0.55, 95% CI = 0.45-0.68).⁴ Results from a meta-analysis showed that summary ORs for the association between 1 standard deviation increments in BD categories and breast cancer risk are 1.52 (95% CI = 1.39-1.66) for percentage dense area in premenopausal women and 1.53 (95% CI = 1.44-1.64) in postmenopausal women.⁵

High BD has been found to lower sensitivity in breast cancer detection.^6-9 Results from a review to evaluate the effect of BD on lesion detection in digital mammography showed that sensitivity to detect breast cancer decreases to between 30% and 64.4% in high-density breasts compared with 80% to 98% in low-density breasts.¹⁰ High interval cancer rates (number of invasive cancer cases after a negative mammography divided by the total number of examinations, exceeding 1 case per 1000 mammography examinations) were found among women aged 70 to 74 years with heterogeneously dense breasts and among those aged 50 to 74 years with extremely dense breasts.² While there is considerable evidence showing the association between breast density, breast cancer risk, and breast cancer screening, little is known about women’s awareness and knowledge of BD.

Breast density notification laws have been adopted in more than 20 states in the United States.¹¹ These laws mandate that providers of mammography services inform patients of their BD, the limitations of mammography to find cancer in dense breast tissue, and the increased risk factor of dense breast tissue. It also advises individuals with dense breasts to talk with their physicians about questions or concerns regarding the summary and whether they might benefit from additional tests (ie, sonogram). In general, these laws have been divisive. There are significant differences found in the language of the laws varying from state to state, and legislated recommendations for possible additional testing are often unaccompanied by legal provisions for insurance coverage.^12,13 It has been reported that patient utilization of screening breast sonography increased after enactment of BD notification, but there was also an increased direct cost for insurers.¹⁴ It has been estimated that for 10 000 women invited to screening from age 50 years for 20 years, about 681 cancers will be found of which 129 will represent overdiagnosis, and 43 deaths from breast cancer will be prevented, influencing the medical decision to recommend additional tests.¹⁵ Results from a survey of physicians within a single primary care network system 10 months after California’s breast density notification law took effect, showed that roughly half of those surveyed (49%) reported no knowledge of BD notification legislation.¹⁶ At the same time, 75% of those surveyed would be interested in more specific education on the subject. Still, little is known about patients’ knowledge and awareness of this legislation and of BD in general.

Knowledge has been defined as familiarity gained by experience of a fact or situation, or as the theoretical or practical understanding of a subject. Awareness is the ability to perceive, to feel, or to be conscious of events, objects, thoughts, emotions, or sensory patterns without necessarily implying understanding. This paper examines published studies that include data regarding BD knowledge (ie, whether women know their own breast density, and whether women know about the association between breast density and health outcomes) and BD awareness (ie, whether women have previously heard about BD).

Methods

We performed a search of the databases PubMed, PsycINFO, and CINAHL. All publication years and all search fields were included. The search was limited to articles in English, and employed specific search keywords. One example of a search strategy used with the PubMed database is [“breast density” AND “knowledge”]. We decided to use broad search terms to make sure we would identify as many pertinent studies as possible. A manual secondary search of all bibliographies from relevant articles was performed to yield further relevant publications. We excluded studies conducted outside the United States.

Articles were reviewed for relevance within the criteria for inclusion as follows: (1) the reports had to quantitatively examine and report (frequency, means, percentages, effect sizes, and/or OR) BD knowledge and/or BD awareness and (2) the number of participants in the sample had to be stated. Books, book chapters, case studies, meta-analyses, comments, and reviews were excluded.

Results

The first database searched was PubMED, followed by a search of PsycINFO and CINAHL. A total of 271 articles were identified from these databases and 6 additional articles were identified from bibliographies, for a total of 277 records (see Figure 1). A search of duplicates was conducted, leaving 234 records that were title- and abstract-screened and 71 articles that were screened in full. The title and abstract screening step evaluated the title and abstract of each of the 234 articles to determine whether they met the following criteria: (1) informed about BD, (2) informed about the sample used (humans), (3) used English as publication language, (4) informed about studies conducted in the United States, and (5) indicated that the publication was peer-reviewed. As part of the full screening step, the articles from the 71 abstracts selected from the title and abstract screening step were obtained and read by 2 readers to determine whether they met the eligibility criteria. These articles were read in full, and 5 were included in the final analysis (see Figure 1). Data on the author, year of publication, sample characteristics, methodology used, measures selected, and quantitative results from each of the articles were abstracted and evaluated.

Figure 1.

Flow diagram of literature review.

Findings are illustrated in Table 1. All studies included in the final analysis were cross-sectional, and used surveys for data collection. Three studies included women younger than 40 years. Three studies recruited participants at medical facilities (eg, breast clinic), and 2 studies were conducted using online services (eg, Amazon Mechanical Turk). Two studies had surveys available in more than one language. All studies included non-white participants. One study had a relatively small sample (<100 participants).

Table 1.

Characteristics of Articles Reviewed.

Author, Publication Date	Sample and Data Source	Measures	Results
Manning et al (2013)18	N = 76; B = 54.5% (42); W = 33.8% (26); O = 10.4% (8); clinic attendees for whom further screening was prescribed following a suspicious screening or diagnostic mammogram (age = 51.28 years)	Awareness: “Do you know what BD is?” 1 (I have never heard about it) to 5 (I know exactly what it is); “Do you know how dense your own breasts are?” (yes/no); if yes 1 (entirely fat) to 4 (extremely dense) Accuracy: Define BD in their own words Risk factor knowledge “Older women are at greater risk for getting breast cancer,” “Women with female relatives who have breast cancer are more likely to get breast cancer;” “There is a gene that makes some women more likely to get breast cancer,” “Women with more dense breasts are at greater risk for getting breast cancer.” 1 (I strongly disagree) to 5 (I strongly agree)	Awareness: All sample: M = 364, SD = 129; W (M = 4.28, SD = 0.94), B (M = 3.29, SD = 1.31), t 64 = 3.11, P < .01, d = 0.87 Accuracy: All sample: M = 2.42, SD = 0.97; W (M = 2.77, SD = 0.93), B (M = 2.27, SD = 0.96) t(67) = 2.07, P < .05, d = 0.53 Correlation accuracy and knowledge: All sample: r = 0.35, P < .01; W (r = 0.46, P < .05), B (nonsignificant) Risk factor knowledge: All sample: M = 3.26, SD = 1.19; by race: nonsignificant Knowledge own BD: All samples: 33.8%; by race: nonsignificant
O’Neill et al (2014)19	N = 344; L = 29; B = 24; W = 235; A = 14; O = 11; with a recent screening mammogram at a tertiary care center (age = 45.71 years)	Knowledge: Whether participants were informed that they had extremely dense breasts; if the participants had heard of BD as a risk factor Talked to providers: If participants’ health providers had spoken to them about BD	Risk factor knowledge: All sample: 62%; First-degree relative (OR = 4.04, CI = 1.26-12.99) Talked to provider: All sample: 32.6%; prior biopsy (OR = 2.43 (CI = 1.21- 4.88) Knowledge dense breasts: All sample: 18.3%; race (OR = 0.26, CI = 0.08-0.93; B vs W); perceived lifetime risk (OR = 0.96; CI = 0.93-0.99)
Rhodes et al (2015)17	N = 1506; L = 11.8%; B = 12%; W = 70.6%; O = 5.5; Online study of screening age women (age = 55.2%)	Knowledge of the masking effect of BD: “If a woman has dense breasts, what impact does this have on the ability of a mammogram to correctly detect cancer? (Easier to see cancer/does not impact/more difficult to see cancer/I don’t know) Awareness: “Have you ever heard of something called BD?” (yes/no) Knowledge of impact on breast cancer risk: “Having breasts that are mostly dense on a mammogram” does or does not put a woman at increased risk of breast cancer	Knowledge of the masking effect of BD (correct response): W 73.1%, B 58.0%, L 77.1%, O67.3% Awareness (yes): W 65%, B 48.5%, L 22.9%, O 54.1% Knowledge of impact on breast cancer risk (correct response): W 57.5%, B 65.5%, L 66.8%, O 51.9%; Knowledge of the masking effect of BD multivariate model—household income OR = 1.10, CI = 1.05-1.15; education OR = 1.22, CI = 1.05-1.42; legislation status OR = 3.82, CI = 1.56-9.32; past biopsy OR = 2.16, CI = 1.38-3.38; awareness multivariate L (compared with W) L: OR = 0.23 (CI = 0.13-0.40), P < .001, B: OR = 0.57 (CI = 0.35-0.93); household income OR = 1.07, CI = 1.03-1.11; education OR = 1.19, CI = 1.09-1.30; diagnostic evaluation OR = 2.64, CI = 1.94-3.58; hormonal therapy OR = 1.69, CI = 1.21-2.38
Trinh et al (2015)20	(Academic facility; 39% were aged 31-50 years, 50% were 51-70 years, 11% were >70 years) N = 105; L = 8%, B = 3%. W = 69%; A = 15%; O = 5% (County hospital; 47% were aged 31-50 years, 59% were 51-70 years, 8% were >70 years) N = 132; L = 51%; B = 3%, W = 20%; A = 21%; O = 5%; women after/waiting for their screening mammography appointments	Knowledge: “Do you know your BD?” (yes/no) Interest in knowledge: “Would you like to know your BD?	Knowledge: 23% yes in academic facility; 5% yes in county hospital (P < .0001); Interest: 94% and 79%, respectively (P < .01); willingness to pay for the supplemental tests at the county hospital compared with those at the academic facility (22% and 70%, respectively, for ultrasound, P < .0001; 20% and 65%, respectively, for contrast-enhanced spectral mammography, P < .0001)
Yeh et al (2015)21	N = 184 (213); L = 9; B = 16; W = 163; O = 9	Knowledge: If participants had been told by their physicians that they had dense breast tissue	Knowledge: 16.8% of women had already been told by their physicians that they had dense breast tissue

Abbreviations: BD, breast density; N, total sample; B, black; W, white; L, Latina; O, other; A, Asian/Asian American; OR, odds ratio; r, Pearson correlation coefficient; d, Cohen’s d.

Breast density awareness (eg, “Do you know what breast density is?”) was assessed in 2 studies. Results from a national survey administered to women aged 40 to 74 years using an online service (N = 1506; mean age = 55.2 years, standard error [SE] = 0.30) showed that 57.5% of participants responded “yes” to the following item: “Have you ever heard of something called breast density?”¹⁷ Women who participated in a small study (N = 77) conducted at a breast clinic responded to the item “Do you know what breast density is?” by using a scale from 1 (I have never heard about it) to 5 (I know exactly what it is).¹⁸ Results showed that the average response to this item was 3.64 (SD = 1.29).

Breast density knowledge (eg, “Does having dense breasts mask the ability of a mammogram to correctly detect breast cancer?”) or knowledge of one’s own BD was assessed in five studies. Rhodes and colleagues¹⁷ reported that 48.6% of women selected the answer “more difficult to see cancer” to the following item: “If a woman has dense breasts, what impact does this have on the ability of a mammogram to correctly detect cancer?” When participants were asked to report their knowledge regarding whether “having breasts that are mostly dense on a mammogram” puts a woman at increased risk of breast cancer, 53.2% agreed with this statement. Manning et al¹⁸ also evaluated BD knowledge by asking participants to indicate their agreement on a scale from 1 (I strongly agree) to 5 (I strongly disagree) with the following item: “Women with more dense breasts are at greater risk for getting breast cancer” (M = 3.26, SD = 1.19). In addition, most participants (58.44%) answered “no” to the following item: “Do you know how your own BD?” As a way to assess “BD accuracy”, women were asked to define BD using their own words, and responses were scored by 3 expert judges using a 1 (not at all correct) to 4 (quite accurate) scale. The mean BD accuracy was 2.42 (SD = 0.97). Women recruited at a breast clinic after a normal mammogram examination (N = 344; mean age = 45.71 years) reported their knowledge regarding BD as a risk factor for breast cancer (62% reported they knew about BD as risk factor), if their health care provider has spoken to them about BD (32.6% reported having discussed BD with their health care provider), and whether they were informed that they had extremely dense breasts (18.3% were told they had dense breasts) after they were provided a description of BD.¹⁹ In another study, women (aged ≥31 years) responded to a survey at an academic facility (N = 105) and a county hospital (N = 132) serving women with high and lower socioeconomic status, respectively.²⁰ Women were asked the following item: “Do you know your breast density?” A greater percentage of women recruited at the academic facility (23%) answered “yes” to this item, compared with those recruited at the county hospital (5%). Most of the participants who answered “no” also reported they would want to know their BD (94% and 79%, respectively). Results from a study conducted online to explore how women respond to the wording of BD notifications (N = 184; mean age = 49.4 years, SD = 8.07) indicated that 16.8% of women had already been told by their physicians that they had dense breast tissue.²¹

Individual differences and associations between BD awareness, BD knowledge, and other sociodemographic and psychosocial variables were assed in all 5 studies. Rhodes and colleagues¹⁷ tested a multivariate model to assess the association between BD awareness and selected variables: household income (OR = 1.07 per category increase, 95% CI = 1.03-1.11), education (OR = 1.19 per category increase, 95% CI = 1.09-1.30), diagnostic evaluation after a mammogram (OR = 2.64, 95% CI = 1.94-3.58), and postmenopausal hormone therapy (OR = 1.69, 95% CI = 1.21-2.38).¹⁷ Similar results were found when a multivariate model of knowledge regarding whether BD makes it difficult to see breast cancer on a mammogram was evaluated: higher income (OR = 1.10 per category, 95% CI = 1.05-1.15), more education (OR = 1.22 per category increase, 95% CI = 1.05-1.42), having had a breast biopsy (OR = 2.16, 95% CI = 1.38-3.38), and residing in Connecticut (OR for Connecticut vs other states = 3.82, 95% CI = 1.56-9.32). This study was conducted in Connecticut, which was the first state to pass BD notification legislation.¹⁷ There were no significant associations between the selected variables (ie, income, education, screening history) and knowledge of impact of BD on breast cancer risk. O’Neill and colleagues¹⁹ reported that knowledge of BD as a risk factor was higher among those with an affected first-degree relative (OR = 4.04, 95% CI = 1.26-12.99). Women with a prior biopsy (OR = 2.43, 95% CI = 1.21-4.88) were more likely to have spoken to their provider about BD. Women with lower perceived lifetime risks were more likely to report that they had been told they had dense breasts (OR = 0.96, 95% CI = 0.93-0.99). After being informed that BD is associated with a higher cancer risk and decreased sensitivity of mammography, 39% of women recruited at an academic facility and 36% of those recruited at a county hospital agreed that this information changed their desire to know their BD.²⁰ In addition, women were asked the following items: “If you found out that you had dense breasts, would you be interested in an additional screening test, such as whole breast ultrasound? (94% of women recruited at an academic facility and 73% of those recruited at a county hospital answered “yes”), and “If you found out that you had dense breasts, would you be interested in additional screening test, like contrast-enhanced spectral mammography, which would require you to have a digital mammography and receive contrast in your vein?” (81% of women recruited at an academic facility and 59% of those recruited at a county hospital answered “yes” to this item). Yeh and colleagues²¹ reported that women perceived significantly greater lifetime breast cancer risk (participants were asked the likelihood they would develop breast cancer in their lifetimes on a scale ranging from 0% to 100%) after being asked to read a sample BD notification as if they had personally received it) (M = 27.82, SE = 1.53) than before (M = 19.79, SE = 1.29). Women were also more likely to intend to undergo mammography after reading the sample BD notification than before, t(183) = 3.29, P < .001, d = 0.25.

Racial and/or ethnic differences in BD awareness and BD knowledge were evaluated in 3 of the studies. Rhodes and colleagues¹⁷ reported that BD awareness was lower among black (OR = 0.57, 95% CI = 0.35-0.93) and Hispanic women (OR = 0.23, 95% CI = 0.13-0.40) when compared with white women in a multivariate model. There was no association between race/ethnicity and BD knowledge (P > .05). Manning et al¹⁸ described a significant difference in BD awareness by race, with greater BD awareness reported by white women (M = 4.28, SD = 0.94) compared with black women (M = 3.29, SD = 1.31), t(64) = 3.11, P < .001, d = 0.87. Results also showed that white women had significantly more accurate BD definitions (M = 2.77, SD = 0.93) than black women (M = 2.27, SD = 0.96), t(67) = 2.07, P < .05, d = 0.53. In addition, it was reported that the correlation between BD accuracy and BD awareness was significant for white women (r = 0.46, P < .05), but not for black women (r = 0.12, P > .05). O’Neill and colleagues¹⁹ found significant associations between knowledge regarding BD as a risk factor for breast cancer, being informed about one’s own high BD, and race. White women were more likely to report BD knowledge (OR = 2.22, 95% CI = 1.15-4.30), and less likely to report that they had been told they had dense breasts (OR = 0.26, 95% CI = 0.08-0.93) when compared with non-white women (N = 109; black = 84, Asian American = 14, Native American/Pacific Islander = 6, more than one race = 5). In the study conducted by Trinh et al,²⁰ while no statistical test was conducted to assess differences in BD knowledge by race or ethnicity, there was a notable difference in the characteristics of the sample by site. Most of the women recruited at the academic facility where white (69%) while most of those recruited at a county hospital were Hispanic (51%). Results from this study showed differences in BD knowledge and interest in BD knowledge by site.

Discussion

Research suggests that BD is an important predictor of breast cancer risk in women. Women who have dense breast are more likely to develop breast cancer than women with low BD. In addition, since cancer and dense breast tissue look similar on a mammogram, dense tissue may make more difficult the interpretation of the results from this imaging test. A large proportion of women in the United States are classified as having dense breasts, but many of them do not know it, or do not know about BD.

This study examined published reports of BD awareness and BD knowledge in women, and we found 5 articles that followed the established criteria. As rates of breast cancer begin to increase after age 40 years, results suggest that women at that age and older tend to have moderate awareness of BD. A low proportion of women know their own BD, and there is lack of knowledge regarding the effect of BD on breast cancer risk and detection. Increased BD knowledge seems to be associated with sociodemographic and screening history factors, such as race, ethnicity, household income, and history of diagnostic evaluation after a mammogram. Results also suggest that the definition and assessments of BD awareness and BD knowledge vary by study. Overall, findings illustrated that there are limited studies on how much women know about factors influencing breast cancer screening.

The present study shows that research is still lacking in the assessment and understanding of specific factors that might be associated with BD knowledge and BD awareness, and disparities in breast cancer screening and mortality. Results from the National Ambulatory Medical Care Survey (N = 8521 visits) showed that white patients received more mammography (P < .05), skin examinations (P < .01), digital rectal examinations (P < .01), and prostate-specific antigen tests (P < .01) than patients of other racial and ethnic groups.²² An analysis of focus group data regarding knowledge of changes in US Preventive Task Force (USPTF)’s mammography screening guidelines in a diverse sample of women shows that there is resistance to guideline changes among these women because the process by which they were revised did not recognize their part in the decision.²³ These findings illustrate the need to increase screening efforts and education initiatives in minority communities. While most studies generally used “large” samples, most samples were primarily white. Findings must be validated in non-white samples, as research suggests that there are racial and ethnic differences in BD. A multivariate model adjusting for body mass index, menopause status, age at first birth, breastfeeding duration, waist circumference, and smoking showed that black women had higher mean percent density when compared with white women (51% vs 43%), P < .01.²⁴ Other studies reached similar conclusions.^25,26 To date, no research has examined BD knowledge and BD awareness in a large and racially/ethnically diverse sample of women as a risk factor for breast cancer.

Our search was limited to peer-reviewed journals, which generally publish articles with significant results. It was also limited to results of BD awareness and BD knowledge published in the Unites States, and in English. Findings cannot be generalized to studies conducted in other countries, and there is a possibility that important elements of BD knowledge and BD awareness in women were not captured in our review. The major strength of this review is that it helped us realize that the evaluation of BD awareness and BD knowledge for the detection and control of breast cancer in women remains largely untested. This finding should open the doors for the development of efforts to promote education regarding breast cancer risk and screening, and to promote health in higher risk women.

Future Direction

The USPSTF states, in their update of the 2009 recommendation for breast cancer, that critical questions remain about how best to manage the association between BD, breast cancer risk and breast cancer diagnosis, and to support women with increased BD.²⁷ While there are many outreach education programs available to assess breast health knowledge and promote breast cancer education in the community, as a way to increase knowledge and participation in screening among women, many of these programs do not consider BD education. In a randomized pretest, posttest experiment conducted in British Columbia, women in the intervention group received information about their BD with the mailed results of their mammogram, along with a pamphlet describing mammographic BD (including photographs showing mammograms of dense and not-dense breasts) and other risk factors for breast cancer, factors that influence BD (ie, age, hormone therapy) and risk-reduction strategies (ie, regular breast screening).²⁸ Results showed that among those who had heard the term, 24.8% in the intervention group described it correctly, 48.6% had a vague answer, and 26.6% described it incorrectly at the 4-week follow-up. The corresponding figures for the control group were 7.5%, 63.8%, and 28.7%. An online study illustrated that, after reviewing a sample dense breast tissue notification and being asked to respond to questions as if they had personally received the notification, women reported greater perceived risk (d = 0.67) and intentions to undergo mammography (d = 0.25) than before.²¹ These findings suggest the need to inform women about BD in general, and about their own BD. We plan to create an enhanced educational intervention for women, focusing on BD awareness, breast cancer risk and breast cancer diagnosis. We also plan to target minority women, as findings from this review suggest that Latinas and black women report lower BD awareness and knowledge than white women. Results from this research will directly affect public health agencies and research on planning and intervention design; as to more effectively promote breast health knowledge and breast cancer detection.

Author Biographies

Marimer Santiago-Rivas, PhD, is a postdoctoral fellow at the Icahn School of Medicine at Mount Sinai. Her research interests include health promotion and cancer disparities.

Shayna Benjamin, BA, is completing a postbaccalaureate premedical program at New York University, and is a volunteer research assistant at the Icahn School of Medicine at Mount Sinai.

Lina Jandorf, MA, is a research professor at the Icahn School of Medicine at Mount Sinai. She is the director of Cancer Community Outreach in the Department of Oncological Sciences as well as the Director of Minority, Outreach, Recruitment and Education (MORE) for the Tisch Cancer Institute.