Does the proven benefit of mammography extend to breast cancer patients over age 70?

BACKGROUND: Prospective randomized studies show reduced breast cancer mortality among women offered mammographic screening; yet, few women 70 or older were represented in these trials. We examine the impact of mammography on stage at diagnosis of breast cancer, over the years when mammography came into general use, comparing women aged 40 to 69 with those aged 70 and older. METHODS: We reviewed the records of 1,001 consecutive patients 40 and older treated for invasive or in situ breast cancer in the surgical practice of one of us (H.S.C.) between 1979 and 1993, comparing trends in mammography use, means of diagnosis, tumor size, axillary node status, and pathology. RESULTS: The proportion of cases diagnosed by mammography increased over time to a comparable degree in both age groups, as did the proportion of T1 and DCIS or microinvasive cancers. This trend toward earlier stage appears entirely due to an increasing use of mammography. CONCLUSION: The potential benefit of regular mammography to healthy women aged 70 and older may equal that observed in their younger counterparts.     

Diagnostic role of mammography and clinical examination in the framework of a screening program for breast carcinoma in Brescia

Screening by mammography is at present the only way to obtain good results in terms of diagnosis of breast cancer at an early stage. In this paper we present the results of first and second rounds of a mammographic and clinical screening programme carried out in the health district of Brescia. At the first round out of 129 cancers detected, mammography was diagnostic in 124 cases; in 82 cases, the examination also allowed the identification of a suspicious nodule, while in 42 cases non palpable neoplasm was diagnosed with mammography alone. In the remaining 5 cases mammography was negative and only clinical examination led to the discovery of breast neoplasms. In the second round, in the 125 cancers detected, mammography was diagnostic in 124 cases; clinical examination allowed the identification of 59 of these tumours, while in 65 cases non palpable tumours were found with mammography alone. Only in one case mammography was negative and clinical examination led to the identification of the tumour.     

Screening fundamentals

While researchers have established the value of screening for breast cancer with mammography, with and without clinical breast examination, age-specific analyses have led to differing opinions regarding the ages and the intervals that breast cancer screening should begin. This article, therefore, provides a detailed, age-specific evaluation of mammography screening by assessing the severity of breast cancer, the effectiveness of earlier versus later treatment, and the accuracy and reliability of mammography. Data from previous randomized trials and other sources are used to evaluate these criteria. The results indicate that screening programs must have high levels of participation, achieve acceptable sensitivity (85%) and specificity (90%), adopt age-specific screening intervals, and consider how disease stage influences diagnosis. In addition, as others have noted, the following benchmarks can be used to evaluate screening programs: (1) more than 50% of screen-detected cancers should be smaller than 15 mm; (2) 30% or more of grade 3 cancers detected on screening should be less than 15 mm; and (3) more than 70% of cancers detected on screening should be node negative.     

Screening women aged less than 50 years with a family history of breast cancer

Family history is an important breast cancer risk factor and is a common reason for referral to specialist breast clinics for consideration of breast screening. The aims of this study were to determine cancer detection rates and prognostic features of breast cancers identified in women aged less than 50 years at increased risk of breast cancer who attend a Family History Breast Screening Clinic (FHC). Between January 1988 and December 1995, 1371 asymptomatic women aged less than 50 years underwent annual clinical breast examination and biennial mammography due to a family history of breast cancer. A total of 29 cancers (23 invasive and 6 in situ) were detected or presented as interval cancer during a mean follow-up of 22 months (range 0-96 months). This gave a relative risk for invasive breast cancer in this high-risk group of 5 when compared with an age-matched female population in the U.K. The cancer screening detection rates were similar to those of women aged 50 years or over undergoing population screening in the NHS Breast Screening Programme (NHSBSP)--FHC prevalent screen 8 per 1000 screening visits versus NHSBSP 6.5 per 1000, FHC incident screen 3.3 per 1000 screening visits versus NHSBSP 3.8 per 1000. A higher proportion of in situ cancers were detected in the FHC screened group compared with cancers identified in symptomatic patients from an age-matched risk group (21% versus 4%). No differences were demonstrated for invasive tumour size, grade or lymph node stage between symptomatic and screened women. The early results of this study suggests that young women at risk of breast cancer due to a family history may benefit from regular breast screening due to the early detection of in situ lesions.     

The effects of health beliefs on screening mammography utilization among a diverse sample of older women

Screening mammography is particularly effective in detecting breast cancer in elderly women. Yet, although half of all breast cancers are diagnosed in older women, statistics show that women aged 65 and over tend to underutilize screening mammography. Prior research has used the constructs of the Health Belief Model to explore attitudes and beliefs relative to breast cancer screening. Prior studies have also identified health beliefs and concerns relative to screening mammography and race/ethnicity as some of the patient-related predictors of screening mammography utilization among younger women. This study uses the theoretical framework of the Health Belief Model to explore the effects of these variables on utilization in a multiracial, multiethnic, random sample of 1011 women, aged 65 and over. Race/ethnicity, belief that mammograms detect cancer, ease the mind, and provide accurate results; concern over the radiation, pain, and cost associated with receiving a mammogram; and other independent variables were tested as predictors of screening mammography utilization. Regression analysis identified that the belief that having a mammogram eases recipients minds was the most significant predictor of screening mammography utilization. None of the other health beliefs or health concerns were significant predictors. Race/ethnicity had no direct effects on utilization nor was it a confounder in the relationship between health beliefs, concerns and utilization. These results indicate that, along with emphasizing the importance of mammograms in early detection of breast cancer, stressing the reassurance that mammography brings recipients may be an effective health education strategy for elderly women of different racial/ethnic backgrounds.     

An ecological study of the effectiveness of mammography in reducing breast cancer mortality

OBJECTIVES: The purpose of this study was to determine the relation of screening mammography to breast cancer incidence and case fatality. METHODS: In a sample of White female Medicare beneficiaries hospitalized in 1990-1991, age-adjusted breast cancer incidence and 2-year case fatality rates were estimated and compared with the frequency of mammographic screening from a population-based survey. RESULTS: The average rates for incidence, case fatality, and mammography within 5 years in 29 states were 414/100,000, 18.8%, and 59.2%, respectively. There was a positive state-level correlation between mammography rates and incidence and an inverse correlation between mammography and case fatality. CONCLUSIONS: High screening mammography rates in some states are associated with reduced breast cancer case fatality rates, presumably as a result of diagnosis of earlier stage cancers.     

Use of 99Tcm-MIBI in the assessment of patients with suspected recurrent breast cancer

A prospective trial was performed to assess the accuracy of 99Tcm-methoxyisobutyl isonitrile (99Tcm-MIBI) scintimammography and X-ray mammography in 18 patients (mean age 58 years, range 46-79 years) with suspected recurrent breast cancer in the breast and/or loco-regional tissues. All patients had been diagnosed to have breast cancer 1-23 years before scintimammography. Two patients had undergone mastectomy, so that a total of 34 breasts were studied with X-ray mammography and with prone-lateral and anterior scintimammography. Any abnormalities on X-ray mammograms and scintimammograms were noted, as was any additional local or nodal uptake of 99Tcm-MIBI. The nature of any lesion seen with either modality, or in which there was a clinical suspicion of recurrence, was confirmed by cytological or histological examination of tissue samples. There were nine breasts with recurrent cancer in eight patients. X-ray mammography identified six of these cancers. 99Tcm-MIBI scintimammography identified eight of nine recurrent breast cancers (the one cancer not seen was positive on X-ray mammography). In the 26 breasts without cancer, two were reported as having changes consistent with cancer and one was reported equivocal. There were three false-positive and one equivocal scintimammograms. The accuracy of 99Tcm-MIBI scintimammography within the breast (85%) was similar to X-ray mammography (82%). Axillary lymph node recurrence occurred in five patients, four of whom were positive with 99Tcm-MIBI. An additional patient had focal uptake of 99Tcm-MIBI at the site of recurrent cancer on the anterior chest wall. In conclusion, 99Tcm-MIBI scintimammography may provide useful complementary information in patients with suspected recurrence of cancer in the breast or loco-regional tissues.     

CD1d-mediated recognition of an alpha-galactosylceramide by natural killer T cells is highly conserved through mammalian evolution

BACKGROUND: Although increasing rates of breast carcinoma incidence have been observed in Asian countries, appropriate strategies for detecting early stage breast carcinoma in such communities have been difficult to formulate, particularly because no large population screening trial specifically involving Asian women has been reported. The objective of this study was to evaluate the effectiveness and quality of mammography as a screening technique for Singaporean women, who are predominantly Chinese. METHODS: In this prospective study, 166,600 women in Singapore ages 50-64 years were randomized to either 2-view mammography without physical examination (67,656) or observation (97,294, controls) over 2 years. RESULTS: Of these women, 28,231 (41.7%) responded and were screened; they were more likely to be married, have more formal education, be working, be Chinese, and be in a higher socioeconomic group (P < 0.001 for all variables). To assess for response bias that could affect outcome, results were also evaluated for nonrespondents (n = 39,425). The incidence rate of cancers among nonrespondents (1 per 1000 woman-years) was less than the 1.3 in women not invited to have screening (P = 0.03, relative risk [RR], 1.3; 95% confidence interval [CI], 1.0-1.7). However, cancers arising from nonrespondents did not differ significantly in stage distribution when compared with cancers within the control group. For every 1000 women screened, 4.8 cancers were detected. The prevalence ratio (the number of cancers detected per 1000 women at first screening divided by the corresponding incidence rate in controls per year) was 3.6 for screened women and 2.4 for women invited to have screening. The majority of cancers detected through screening were early stage, with 64% as either ductal carcinoma in situ (26%) or Stage I disease (38%) and was significantly more than the corresponding 26% in women not invited to have screening (P < 0.001). When only invasive cancers were considered, screened women still had more early cancers, with 65% having no lymph node involvement, compared with 47% in the group not invited to have screening (P = 0.001; RR, 1.4; 95% CI, 1.2-1.7). Women who were screened had half the risk of having Stage II or later cancers (P < 0.0001; RR, 0.5; 95% CI, 0.4-0.7) when compared with women not invited to have screening. This higher detection rate of early cancers through screening was accomplished with acceptable recall rates of 8% for further mammographic films or physical examination and a biopsy rate of 1.0% (10 per 1000 women screened). The interval cancer rate was 2.1 per 10,000 women screened in the first year of follow-up. CONCLUSIONS: These positive results of intermediate measures suggest that, in Asian communities, screening mammography could be an important modality for detecting early stage breast carcinoma. However, the low compliance rates suggest that health education efforts must focus on issues related to acceptability if such programs are to succeed.     

Mammography versus clinical examination of the breasts

Using published data from screening trials, this article compares two-modality (mammography and clinical examination) and single-modality (clinical examination alone) screening by evaluating cancer detection rates, program sensitivities, mode of cancer detection in two-modality screening, nodal status at time of detection, survival 10 years post-diagnosis, and breast cancer mortality 10 years after entry. Consistently, two-modality screening achieved higher cancer detection rates and program sensitivity estimates than either modality alone; mammography alone achieved higher rates than clinical examination alone; interval cancer detection rates between screening examinations were higher following clinical examination alone than mammography alone; single-modality screening with mammography failed to detect breast cancers identified by clinical examination alone; the sensitivity of mammography was lower in younger than older women, while the reverse was true for clinical examination; and mammography identified a higher proportion of node-negative breast cancer than clinical examination. We conclude that combining clinical breast examination with mammography is desirable for women age 40-49 because mammography is less sensitive in younger than older women. Careful training and monitoring are, however, as essential with clinical examiners as with mammographers.     

The "epidemic" of breast cancer in the U.S.--determining the factors

Breast cancer incidence rates in the United States rose by 24% between 1973 and 1991. Mortality during this period, however, remained stable. Both the 5-year relative survival rate and the rates of in situ and stage I breast cancers have been increasing, while the incidence of later-stage cancers has been decreasing. Increased mammography screening may explain the documented jump in breast cancer incidence rates during the mid-1980s. Differences in the distribution of breast cancer risk factors may account, in part, for the temporal trends in breast cancer incidence. In particular, breast cancer risk factors may vary by birth cohort, including age at menarche, age at first birth, physical activity, obesity, diet, alcohol intake, estrogen therapy, and exposure to environmental organochlorines. After decades of epidemiologic research, a preventive approach to breast cancer that focuses on the physiologic effects of the sex steroid hormones, and their potential interactions with family history, is being carefully formulated.     

Breast cancer screening of the medically underserved: results and implications

Socioeconomic status is the most significant factor influencing the decreased survival associated with breast cancer in minority groups in the United States. Barriers to the use of early detection programs by low-income women often result in the detection of breast cancer at stages too advanced to assure optimum outcomes. In an effort to increase accessibility of breast cancer screening among such individuals, the Early Detection Program (EDP) was initiated in 1987. The program provided breast cancer screening to women 40 years of age and older who attended eight primary healthcare centers located in low-income neighborhoods throughout Dade County, Florida. From its inception in October 1987 through December 1993, 23,866 medically underserved women had mammography examinations, with more than 17,000 of these women undergoing baseline mammograms. Since the program's inception, 126 cancers were diagnosed in 123 women. A dramatic shift from later to earlier stage breast cancers was observed. These results warrant a greater inclusion of medically underserved and lower socioeconomic status women in screening programs for the early detection of breast cancer.     

Use of screening mammography and its demographic and risk determinants in women 25 to 65 years of age

BACKGROUND: To know the utilization of the screening mammography among women from 25 to 65 years old in an urban health zone, where there is not an specific screening program for breast cancer. To detect the demographic and risk determinants that are involved in the mammography screening use. SUBJECTS AND METHODS: A sample of 1,240 women were interviewed consecutively as they visited their physician. Risk factors, sociodemographic variables and use of health services were analyzed. The associated variables with the use of mammography screening were determined by univariant analysis. A multiple logistic regression model was designed to identify the variables independently associated with the use of mammography screening. RESULTS: The percentage of interviewed women who have completed at least one mammography screening in the last three years has been 10.2 +/- 3% (confidence level: 95%), 68.3% of them were under 50 years old. The variables independently associated with the use of mammography screening were: age (OR = 1.08); routine visit to the gynecologist (OR = 8.13); educational level (primary: OR = 2.44, secondary: OR = 3.66, university: OR = 7.43, no schooling: reference level); and knowledge about the benefits of mammography screening (OR = 6.15). Family history of breast cancer and the other risk factors were found not to be associated with the use of mammography screening. CONCLUSIONS: The use of mammography screening among women from 25 to 65 years is inadequate according to the age and other risk factors. Mammography screening among women with a family history of breast cancer and those over 50 years old is underused, so it would be recommended and their use increased for these women. But women under 40 years old without family history of breast cancer have to be dissuaded from undertaking such a screening.     

Can mammography screening explain the race difference in stage at diagnosis of breast cancer?

BACKGROUND: A race difference in the stage at diagnosis of breast cancer is well established: African American women are less likely than white women to be diagnosed at a localized stage. The purpose of this study was to determine the extent to which the observed race (black/white) difference in stage at diagnosis of breast cancer could be accounted for by race differences in the mammography screening history. METHODS: This was a population-based, retrospective study of 145 African American and 177 white women with newly diagnosed breast cancer in Connecticut, between January, 1987 and March, 1989. Cases were ascertained through active surveillance of 22 Connecticut hospitals. RESULTS: Black women were diagnosed more commonly with later stage cancer (TNM stage > or = II) (age-adjusted odds ratio [OR] = 2.01, 95% confidence interval [CI] 1.24-3.24) than were white women. Blacks were also more likely than whites to report that they had not received a mammogram in the 3 years before development of symptoms or diagnosis (OR = 2.05, 95% CI 1.26-3.35); this association was not altered substantially with adjustment for socioeconomic status. In race-specific analyses, mammography was protective against later stage diagnosis in white women, but not in black women. With adjustment for mammography screening, the OR for the race-stage association was reduced only minimally, and race remained a significant predictor of stage at diagnosis. CONCLUSIONS: In these population-based data, history of mammography screening was not an important explanatory variable in the race-stage association. Specifically, history of mammographic screening accounted for less than 10% of the observed black/white difference in stage at diagnosis of breast cancer.     

A health priorities model: application to mammography screening

This study describes and empirically tests a health priorities model. This model predicts underuse of regular mammography screening among adult women within the larger health context in which such decisions are made. The model incorporates women's comparative illness threats, comparative importance of health behaviors, and demographic variables. A telephone survey was conducted with a sample of women (N = 887) older than 50, in 40 rural communities in the state of Washington. Logistic regression analyses showed that women who perceived themselves at low risk for getting breast cancer and/or who perceived another disease (i.e. heart attack) as an equal or greater threat than breast cancer were less likely to be regular screeners of mammography. In addition, women who perceived other health behaviors as more important than regular mammography screening were less likely to be regular screeners than those women who perceived regular mammography screening as more important. Current or anticipated health problems were not related to screening behavior. The results are discussed in light of the practical, theoretical, and empirical implications.     

The North Carolina Breast Cancer Screening Program: foundations and design of a model for reaching older, minority, rural women

Breast cancer screening programs do not reach all women at the same rate. Screening mammography use varies according to sociodemographic characteristics; mammography utilization is highest among women in their fifties but then decreases with age. In North Carolina, breast cancer is a particular burden for Black and lower-income women. Black women are more likely to be diagnosed with late stage disease, and their rate of breast cancer mortality is higher than it is for White women even though the incidence in White women is greater. Older, Black, and low-income women are less likely to obtain screening by mammography and clinical breast examination. The Black-White gap is even more pronounced among rural women, in part because they are more likely to be poor. The North Carolina Breast Cancer Screening Program (NC-BCSP) was established to increase the rate of regular mammography screening by an absolute 20% in 3 years among older Black women ages 50 and older in five rural counties in the eastern part of the state. In this paper, we describe the genesis of this comprehensive community intervention model, highlighting the behavioral science constructs, health education principles, and theories of behavioral and organizational change that form its conceptual foundation. NC-BCSP's theoretical foundations include the social ecological perspective, the PRECEDE model of health promotion, the Health Belief Model of individual change, and the "stages of change" transtheoretical model. We also review the experiences and lessons learned from two previous outreach initiatives in North Carolina that provided valuable "lessons" in the development of the NC-BCSP intervention model. In the second half of the paper, we describe the actual NC-BCSP interventions, activities, and evaluation tools, citing specific examples of how the underlying theories are implemented. NC-BCSP's goal goes beyond individual behavior change to raise low mammography screening rates among Black women in rural North Carolina. Its ultimate objective is to create linkages across agencies, and between agencies and communities, that will endure after the research project ends.     

Endoscopic surveillance of Barrett's esophagus: a cost-effectiveness comparison with mammographic surveillance for breast cancer

OBJECTIVE: Endoscopic surveillance of Barrett's esophagus is commonly practiced to detect malignancy in an early and curable stage. However, the cost-effectiveness of this practice has been questioned. To clarify this issue, we undertook a cost analysis of endoscopic surveillance to detect adenocarcinoma in Barrett's esophagus compared with mammography used to detect occult carcinoma of the breast, a widely accepted cancer surveillance technique. METHODS: The rate of esophageal adenocarcinoma detected by endoscopic surveillance was calculated for Duluth Clinic patients with Barrett's esophagus seen from 1980 to 1995 and compared with published rates. The rate of occult breast cancer detection was calculated for all women undergoing surveillance mammography at the Duluth Clinic for the year 1994 and compared with published rates. Costs for screening studies and therapy for cancer treatment for both cancers were calculated based on clinical results and assumptions regarding outcomes derived from published reports, and the costs were compared. RESULTS: Endoscopic surveillance of 149 patients with benign Barrett's esophagus was performed for a total of 510 patient-yr, during which time seven patients developed adenocarcinoma, an incidence of one case per 73 patient-yr of follow-up. Occult breast cancer was detected in 50 of 12,537 mammograms, a detection rate of 0.4%. The incidences in both cases were comparable to published figures. The costs of detecting a case of adenocarcinoma in Barrett's esophagus and occult breast cancer were $37,928 and $54,513, respectively, and those for treatment resulting in cure were $83,340 and $83,292. Cost per life-yr saved was $4,151 for adenocarcinoma in Barrett's esophagus and $57,926 for breast cancer. CONCLUSION: Endoscopic surveillance of patients with Barrett's esophagus compares favorably with the common practice of surveillance mammography to detect early breast cancer, and should therefore be considered to be as cost-effective as surveillance mammography.     

Effect of a community health center intervention on breast cancer screening among Hispanic American women

OBJECTIVE: A multiple component intervention in a community health center is presented, and its effect on breast cancer screening participation by Hispanic American women between the ages of 45 and 75 years is discussed. DATA SOURCES/STUDY SETTING: In 1990, data were collected through a retrospective audit (at least as far back as 1987) of community health center medical records, as well as from a client referral log. The health center, located in a small Massachusetts city, primarily serves clients of Latino heritage. STUDY DESIGN: The study used a nonexperimental pretest-posttest intervention design to document clients' screening activities. To control for uneven length of enrollment, aging of the population, and sporadic utilization, the unit of analysis chosen for the principle study variables was an "eligible year." DATA COLLECTION: Variables of interest included screening (clinical breast exam and mammography), periodicity of screening, and compliance with referrals. PRINCIPAL FINDINGS: Postintervention, considerably greater screening mammography occurred among all age groups, more women had at least one screening mammogram during the period, more clinical breast exams included a mammogram referral, and the compliance rate improved. The rate of clinical breast exam did not significantly improve, showing a downward trend.     

Increases in ductal carcinoma in situ (DCIS) of the breast in relation to mammography: a dilemma

The increased use of screening mammography has resulted in a marked increase in detected cases of ductal carcinoma in situ (DCIS) of the breast since the early 1980s. In 1993, there were an estimated 23,275 newly diagnosed cases of DCIS in the United States, of which 4,676 were in women aged 40-49. DCIS accounted for 14.7% of all newly diagnosed breast cancers in women aged 40-49 in 1993, and perhaps 40% of all mammographically detected breast cancers in this age group are DCIS. Among women aged 40-49, an estimated 1,890 mastectomies and 2,707 lumpectomies (with or without radiation) were performed for DCIS in 1993. There is an urgent need to better understand the relationship of mammographically detected DCIS to invasive and potentially life-threatening breast cancer. Better information about the appropriate treatment of DCIS is also needed to reduce the confusion and uncertainty many women and their physicians currently experience in the face of a DCIS diagnosis. For the present, women considering screening mammography should be told the likelihood of being diagnosed with DCIS and that only some DCIS cases may be clinically significant but almost all will be treated surgically.     

A new, more invasive approach in the radiation diagnosis of breast cancer

The authors discuss the state-of-the-art techniques and the increasingly invasive approach to the diagnosis of breast diseases and also summarise their own experiences. Special attention is called to the nonpalpable, preclinical stage of breast cancers. The newest techniques like MR-mammography, stereo-taxic and ultrasound directed cytology and core biopsy are demonstrated, as well as the present place of traditional breast imaging methods: mammography and diagnostic ultrasound. The preoperative localisation of nonpalpable cancers improves the safety of surgical procedures. The authors emphasize the importance of the detection of early breast cancer, for the sake of a more favourable prognosis compared to that of the palpable, advanced cases. The results of mass screening is detailed, based on statistical data.     

Biological parameters in major depression: effects of paroxetine, viloxazine, moclobemide, and electroconvulsive therapy. Relation to early clinical outcome

Mammography, whilst remaining the first line imaging investigation of suspected primary breast cancer, can be difficult to interpret in patients with fibrous or dense breasts. Radionuclide imaging of the breast (scintimammography) has been suggested as an additional test. The aim of this study was to perform prospectively a comparison of the two techniques in a population with suspected breast cancer. Seventy such patients, mean age 54 years (range 57 years, 28-85) with 74 suspicious breast lesions were studied. They were imaged 5-10 min after intravenous injection of 740 MBq of Tc-99m sestamibi. Prone lateral and anterior supine views with and without markers were performed. All patients had histological confirmation of the nature of the breast lesions by limited incisional biopsy or definitive wide local excision, or cytological confirmation on fine needle aspiration. All patients had X-ray mammography. There were 53 malignant breast tumours and 21 benign lesions. Scintimammography correctly diagnosed 47 breast cancers, and yielded true-negative results in 12 benign breast lesions. There were six cases of false-negative results and nine false-positive results. Four scans were reported as equivocal. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 89%, 52%, 84% and 67%, respectively. X-ray mammography diagnosed correctly 37 malignant tumours, and in 12 benign lesions the results were true negatives. Ten studies were reported as equivocal. The sensitivity, specificity, PPV and NPV were 70%, 57%, 80% and 43%, respectively. The accuracy of Tc-99m sestamibi scintimammography was better than X-ray mammography though this was not significant (McNemar's test). Fewer equivocal results were obtained with scintimammography. Scintimammography may therefore have a role in the diagnosis of primary breast cancer when X-ray mammography is equivocal or unhelpful.