To our knowledge, this study was the first comprehensive community-based evaluation of the first mammography experience, including both screening and diagnostic mammography, among women younger than 40 years. In our population, a substantial percentage of young women received screening mammography, but few breast cancers were found, regardless of their specific age, race, or individual characteristics. Yet, these women experience high recall rates with high rates of additional imaging. The sensitivity, specificity, and screening positive predictive value of screening mammography were poor, and cancer detection rates were very low in these young women, who are not yet in an age group for which national organizations recommend regular screening mammography. Harms need to be considered, including radiation exposure because such exposure is more harmful in young women (22
), the anxiety associated with false-positive findings on the initial examination, and costs associated with additional imaging. If we consider a theoretical population of 10
000 women aged 35–39 years, then from our results, an average of 1266 women who are screened will receive further workup, with 16 cancers being detected and 1250 false-positive examinations. This cancer detection rate corresponds to an estimated 79 workups for each cancer detected. Using the same methods that were outlined above, we also considered two theoretical populations of women who underwent their first mammography at the ages of 40–44 years or 45–49 years. The number of workups per cancer detected was estimated to be 66 in the age group of 40–44 years and 40 in the age group of 45–49 years. Performance characteristics were good for diagnostic mammography, as expected because most young women undergoing diagnostic mammography reported the presence of a breast lump and because diagnostic mammography performance improved when a lump was reported.
It is unclear why the first mammogram for some women with a breast lump was classified as a screening mammogram, and for others, it was classified as a diagnostic mammogram. Women reporting a breast lump constituted a small proportion of the screening mammography population (5%) but were different from the women reporting a lump in the diagnostic mammography population (ie, the specificity and the cancer detection rate among women with a lump who received a screening mammogram was observed to be lower than that among women with a lump who received diagnostic mammography). Unfortunately, we could not evaluate when the lumps were detected. For example, it is possible that among women with a breast lump, some made a screening appointment and then developed a lump that was then reported at the time of screening, whereas others with a lump may have sought an immediate consultation for a new breast symptom, without having scheduled a mammogram. The subgroup of women arriving for screening with a lump need further study because they appear to be a clinically distinct group.
The majority of women who were younger than 40 years at their first screening mammogram (67
468 [77.7%]) had no family history of breast cancer in a first-degree relative, in particular women aged 35–39 years (80.7%). We caution against screening young women with a positive family history of breast cancer, unless there are characteristics that are associated with an inherited predisposition to breast cancer at a very young age; we make this recommendation because performance characteristics were similar in women with a family history of breast cancer and in women without such history. Women with a family history of breast cancer, compared with those without such history, had higher recall rates but equal cancer rates and cancer detection rates. Some women and/or their providers may be requesting a baseline mammogram, most likely a holdover from historical American Cancer Society guidelines (12
). It is also possible that the women and/or their providers think that they are at high risk and can benefit from screening. Kapp et al. (25
) used data from the National Health Interview Survey and found that women aged 35–39 years who had a mammogram reported a physician recommendation for a mammogram regardless of risk factors. Risk factors, however, were more likely to explain reported phyisician recommendations for mammography for women aged 30–34 years.
To understand the level of performance reported in this study, we compared these results in young women (aged 18–39 years) with results from women in the BCSC who were aged 40–44 years and 45–49 years and who had their first screening mammogram in the BCSC. Mammography performance measures in young women (aged 18–39 years), except for specificity, were inferior to those in women aged 40–49 years. Age-adjusted sensitivity of first screening mammography was lower among young women (76.5%) than among women aged 40–44 years (82.4%) or 45–49 years (87.3%). The cancer detection rate among women aged 18–39 years was 1.7 cancers per 1000 mammograms, among those aged 40–44 years was 2.3 cancers per 1000 mammograms, and among women aged 45–49 years was 4.3 cancers per 1000 mammograms. This cancer detection rate in young women may be higher than expected in comparison to incidence rates because data were from first mammograms. The poor performance of screening mammography among younger women is likely attributed to the very low cancer prevalence in this group. Most of the young women have dense parenchymal tissue that may mask tumors, and so breast density may also contribute to the lower performance of mammography in young women.
Consistent with previously published work (3
), pathology results indicated that tumors from most young women compared with tumors from older women have poorer prognostic characteristics, higher stage, higher proportion of positive lymph nodes, and higher proportion with an estrogen receptor–negative and progesterone receptor–negative status. Although the young women in our population had a higher proportion of cancers with poor prognostic characteristics, they also had poor mammography performance indicators with low sensitivity, specificity, and cancer detection rate. These results pose challenges to screening decisions. African American women have higher cancer rates and poorer outcomes than white women (27
). Young African American women are screened at a higher rate than white women (31
), which could be explained by physicians giving greater importance to the relative risk of a diagnosis before age 40 years than to the absolute risk and by the perception that because a high level of cancers with poor prognosis are found among young African American women, earlier screening is required for this group (32
). Our findings support a need for serious discussion about the appropriateness of mammography in women without the presence of symptoms. The results for diagnostic mammography are much better for all young women perhaps because 70% report the presence of a lump at the time of testing. Symptomatic women should receive mammography.
Few community-based studies have been conducted to evaluate the performance of mammography among young women. The Oregon Breast and Cervical Cancer Program (BCCP), which targeted women at the poverty level, has reported that 21% of women who were younger than 40 years were asymptomatic but that 79% of their women who were sent mammography had been examined for a breast problem, which is a much smaller proportion than were examined by screening in our population (33
). Discrepancies between that study and this study might be that data for this study were from all women in participating practices, whereas data in the BCCP study were from women who were eligible for that study (ie, those with incomes of up to 250% of the Federal Poverty Level and who were uninsured or underinsured). Thus, mammographic screening of asymptomatic women is not supported and should be reserved for young women with symptoms.
Breast ultrasound and breast magnetic resonance imaging are increasingly used in young women (34
), yet to date there are no community-based evaluations of the performance characteristics or demonstrations of a reduction in morbidity and mortality. Both of these modalities would be important in lowering the radiation dose to young women.
This study has several limitations. First, because our data reflect clinical practice, we had a sizeable amount of missing data for breast density and pathology characteristics. Density data are largely missing as a result of practice-specific nonreporting, and pathology characteristics are missing when they are not reported on the pathology reports to the cancer registries and/or are specific to a hospital or pathology laboratory. Second, we could not collect the complete family pedigree or BRCA1 or BRCA2 status of those in our study, which prevents us from identifying women at very high risk. Finally, we do not know the outmigration of women from the region in which they were diagnosed within 12 months of their mammogram. This percentage is expected to be small, and most women with a positive mammogram complete their workup within a month. The major strengths of our study include the representative community-based nature of the BCSC, the large sample size, and prospective cancer follow-up through linkages with local registry and/or pathology databases.
Future research should explore the association of symptoms with accuracy and health-seeking behavior. In addition, research should provide guidance on defining which young women might benefit from screening mammography and on the role and use of advanced technologies to detect breast cancers in younger women.
In conclusion, young women have received screening mammography, but few cancers have been detected, regardless of their specific age, race, or other individual characteristics. With high recall and low cancer detection rates, many young women, who are at low or average risk for breast cancer, are having additional imaging as a result of undergoing screening mammography, with a low probability of cancer detection. Who should be screened for breast cancer at younger ages and how best to screen them remain important research questions. Cancers in young women, across the board, have characteristics associated with more rapid tumor growth and poorer prognosis than those in older women. Tumor characteristics with poorer prognostic characteristics pose a dilemma: It is important to find breast cancers in young women early because of the underlying tumor biology of such cancers; yet current screening performance is challenged by the high breast density, which is generally found in young women. Research results evaluating the performance of the addition of ultrasound and/or breast magnetic resonance imaging in young women at high risk for breast cancer are needed to show whether these modalities perform better than mammography alone in young women.